Abstract:

A brief introduction will be given to Artificial Intelligence (AI) with a special emphasis on how it does differ from Human Intelligence (HI). Humanoid Robot, the most difficult one out of all the robots to analyze and control, will be used as a Robotic Soldier. A robotic soldier will have to negotiate varying rough terrains in the field, as the situation demands, by consuming minimum energy and after maintaining its dynamic balance. For the said purposes, a robotic soldier must be equipped with adaptive motion planner, gait planner and controller, and for their development, the assistance of AI is a must. This lecture will deal with the steps to be followed to achieve this milestone, and highlights a few open research issues, till date.

Bio-sketch:

Dr. Dilip Kumar Pratihar received his BE (Hons.) and M. Tech. in Mechanical Engineering from Regional Engineering College (now, National Institute of Technology) Durgapur, in 1988 and 1994, respectively. He obtained his Ph.D. from Indian Institute of Technology Kanpur, in 2000. He received University Gold Medal, A.M. Das Memorial Medal, Institution of Engineers’ (I) Medal, INSA Teachers’ Award 2020, New Code Of Education 2021 Award, Distinguished Alumnus Award 2021 from National Institute of Technology Durgapur, Institute Chair Professor Award 2022 from IIT Kharagpur, and others. He was included among the World’s Top 2% Scientists in the areas of Image Analysis and Artificial Intelligence in a survey carried out by Stanford University, USA, in 2020, 2021, 2022. He was declared Outstanding Researcher 2021 in www.research.com. He completed his post-doctoral studies in Japan, and then, in Germany under the Alexander von Humboldt (AvH) Fellowship Programme. He received the Shastri Fellowship (Indo-Canadian Fellowship) to work on humanoid robots. He is working now as a Professor (HAG scale) of IIT Kharagpur. He has made significant contributions on the fundamentals and applications of Artificial Intelligence in Industrial Automation, Robotics, Health Care, Education Technology, and others. He has published more than 180 research papers in peer reviewed international journals and 100 papers in conferences and national journals. He has contributed 23 chapters in edited international books. A few of his fundamental contributions published in IEEE, ASME, Elsevier, Springer journals are being highly cited by researchers in the field. He has written the textbooks on “Soft Computing”, “Fundamentals of Robotics”, co-authored another textbook on “Analytical Engineering Mechanics”, edited a book on “Intelligent Autonomous Systems”, co-authored four reference books on “Modeling and Analysis of Six-legged Robots”, “Modeling and Simulations of Robotic Systems Using Soft Computing”, “Modeling and Analysis of Laser Metal Forming Processes by Finite Element and Soft Computing Methods” and “Multi-body dynamic modeling of multi-legged robots”. His textbook on “Soft Computing” has been translated into Chinese language also. He has developed three on-line NPTEL courses, such as “Traditional and Non-Traditional Optimization Tools”, “Robotics” and “Fuzzy Logic and Neural Networks”. He has guided 25 Ph.D. s, and 11 more Ph.D. students are working now under his guidance. He has filed three patents and been granted Copyright for his novel intelligent optimization tool named Bonobo Optimizer. He has completed a number of sponsored projects funded by the DST, DAE, DBT, MHRD, MeitY, Government of India, and two consultancy projects of the industries. He is in editorial board of a few International Journals. He is an Associate Editor of one International Journal. He has been elected as a Fellow of Institution of Engineers (I), MASME and SMIEEE.

Abstract:

Droplet wetting and evaporation are ubiquitous in nature and technology. A surface exposed to the environment invariably goes through these phenomena. Several textured surfaces of plants and animals exhibit dewetting properties, and this property may be leveraged in applications such as drag reduction, anti-snow adhesion surfaces, self-cleaning surfaces, and water harvesting. In the context of the evaporation, applications include inkjet printing, surface coating, biosensors, and spray evaporative cooling. In this seminar, I will present my research on two topics, i.e., Droplet wetting on microtextured surfaces and Droplet evaporation. The wetting on microtextured surfaces having the geometry of honeycomb hexagon cavities, micro-grooves, and varying pitch micro-pillars will be presented. The droplet wetting behavior on these different geometries and the effect of their shape and size of the microtexture on spreading and controlling the motion dynamics of the droplet will be shown. In the context of droplet evaporation, a study of pinned sessile droplet evaporation on a heated hydrophilic substrate will be presented, which uses numerical and experimental methods. A two-way coupled numerical model/solver based on the Finite Element Method will be discussed, which accommodates for evaporative cooling and substrate heating.

Bio-sketch:

Dr. Manish Kumar is a Postdoctoral research fellow at the Transfers, Interfaces and Processes (TIPs) Laboratory of Université Libre de Bruxelles in Belgium. He is currently working on "DynWet" project funded by Fonds National de la Recherche Scientifique (FNRS), Belgium, to study the effects of evaporation on dynamic wetting of volatile liquids. He received his Ph.D. from the Department of Mechanical Engineering at IIT Bombay in 2020 and M.Tech. in Thermal Engineering (CFD & HT) from NIT Hamirpur in 2013. He has also worked as Assistant Professor at JSS Academy of Technical Education Noida for three semesters after completing his M.Tech. and before joining the Ph.D. program. He has a keen interest in research topics involving interfacial transport, multi-scale and multi-physics phenomena such as wetting, evaporation, and microfluidics. He uses experimental as well as numerical methods to conduct the research work. His work has been published in prestigious international journals such as Langmuir, Scientific Reports, Physics of Fluids, and International Journal of Heat and Mass Transfer. He received travel grant awards from APS-DFD, DST-SERB, and CSIR to present his research work at International conferences in US and UK.

Abstract:

Exactly, two hundred years ago, in 1822, it was discovered that there exists a pressure and temperature condition on the Phase Diagram, later identified as the Critical Point (CP), beyond which the liquid and vapor states are indistinguishable. However, it is now well accepted that the Supercritical (SC) fluids have two distinct states – “liquid-like” and “gas-like” and their thermophysical properties exhibit anomalous behavior above CP. We highlight that this anomalous behavior extends to pressures and temperatures much below the critical values; indeed, the anomalous region starts within the subcritical liquid state and extends well into the SC region. It is also revealed that two to three orders-of-magnitude enhancements in gaseous heat transfer is possible by moving from subcritical to high-SC pressures, the effect being more pronounced at lower temperatures. Additionally, since the dynamic viscosity at SC pressures is much lower than that of liquid, the flow work goes down significantly. Motivated by many applications, extensive research has been devoted to thermal transport by SC water and CO2. However, these fluids are reactive and corrosive, and require much higher pressures. We present Argon as an alternative SC fluid for thermal transport, whose critical pressure is lower (Pc = 47.994 atm) and it can even work as a SC fluid under subzero temperatures (Tc = -122.5°C). Argon is non-reactive, non-corrosive, and environmentally-benign. Indeed, fluids under SC conditions can find widespread emerging/future applications in terrestrial, space, and lunar systems.

Bio-sketch:

Dr. Prasad’s research interests include convective heat transfer, heat transfer in porous media, supercritical fluids and heat transfer, energy materials/devices, and advanced materials processing and manufacturing. He has published over two hundred twenty invited/refereed articles and made over two hundred conference/seminar presentations. As a PI/Co-PI, Dr. Prasad has received more than $25 million in grants and contracts from US federal agencies and industry. He has mentored/advised sixteen doctoral students, twelve post-doctoral fellows, six visiting scientists, and numerous masters students. Several of his doctoral and post-doctoral advisees are serving as faculty at major research institutions in the US, India, and China. He is the recipient of many US and international awards, including the 2020 Heat Transfer Memorial Award from American Society of Mechanical Engineers. Dr. Prasad’s academic positions include Assistant/Associate Professor at Columbia University, Professor/Leading Professor of ME and Professor of Materials Science and Engineering at Stony Brook, Distinguished Professor of MME at Florida International University (FIU), and Distinguished Visiting Pfrofessor and Adjunct Professor at Indian Institute of Technology, Kanpur. In the academic leadership role, Dr. Prasad has served as the President of Mody University of Science and Technology (India), Vice President for Research and Economic Development at UNT, Executive Dean/Dean of Engineering and Computing at FIU, Interim Dean of Engineering at Wichita State, and Associate Dean of Engineering for Research and Graduate Studies at Stony Brook. Currently, he serves as a member of the Board of Directors of American Society of Thermal and Fluid Engineers and the lead Editor-in-Chief of the Annual Review of Heat Transfer (2002-present).

Abstract:

The roles of rare earths (RE) in global economy, technological advancement and national security are being increasingly recognized and has been strongly underscored by the global trend to transition to a cleaner society. Rare earth elements for Nd-Fe-B and Sm-Co permanent magnets are central to devices and machineries for data storage, clean transportation, wind energy, consumer electronics, medical systems, national defense, etc. They are indispensable for the ongoing Net-Zero world effort for accelerating the decarbonization of energy systems. However, most countries excessively depend on vulnerable supply chains for rare earths. This is even more critical considering that Nd-Fe-B magnets, widely used in many applications, is regarded as subject to supply disruption relative to the projected demand for applications. High performance permanent magnets need suitable intrinsic magnetic properties and proper microstructure for extrinsic properties development. Many potential RE-lean and RE-free permanent magnet candidates show good intrinsic magnetic properties, including high magnetization, large or moderate magnetic anisotropy, and high Curie temperature, all of which can potentially be exploited for the development of novel permanent magnets. However, they are metastable which leads to the formation of local structural defects, secondary soft magnetic phases, or decomposition at high temperature. Hence it has not been possible to transform their promising properties into practical applications. This talk focuses on challenges and opportunities for developing permanent magnets. It will include trends for current commercial magnets. It will also include the strategy for composition and microstructure design and the development of novel synthesis routes to maximize the coercivity and mitigate the challenge of the metastable behavior of the magnetic phases in new formulations. Opportunities in additive manufacturing of magnets will be discussed.

Bio-sketch:

Ikenna Nlebedim is a scientist at Ames Laboratory and a deputy lead in the Developing Substitutes focus area of the Critical Materials Institute. He is also an adjunct faculty member at Iowa State University. He obtained his Ph.D. from Cardiff University, United Kingdom. Ikenna’s research has focused on the development, modeling and functionalization of magnetic materials, including rare earth permanent magnets for different applications. As a principal investigator and group leader at Ames Laboratory, he led the multi-institution national research effort that produced the first Made-in-America rare-earth magnet within 20 years, using materials sourced entirely from the United States. Also, he leads a group of researchers developing recycling technologies for rare earths, lithium, cobalt and other critical elements. He led the research effort that developed the novel environmentally-friendly acid-free dissolution recycling process. Ikenna’s research has received R&D100 awards, Federal Laboratory Consortium award, TechConnect Innovation awards, Research Excellence award and Ames Laboratory Inventor awards.

Abstract:

Traditionally, the usage of mechanical transmission concepts that offer high reduction ratio in a compact space has been limited to very low, intermittent power applications. Efficiency less than 70% further discourages allocation of the limited research and development funds that are usually directed towards making conventional planetary gear trains (PGT) more reliable. The continued push for electrification and sustainability has however, renewed the interest in compact power dense and quiet mechanical trans- mission solutions, especially in aviation, wind energy, and ground transportation sectors. To meet the aggressive power density targets, for example 8 hp/lb for rotor-crafts, it is imperative to explore configu- rations different from conventional PGTs. The research work attains three of the goals in the development and de-risking of a high reduction ratio transmission (HRT) technology: (i) mature the component level design analysis tools based in the fun- damentals of contact mechanics, FEM, multi-body dynamics, and tribology (ii) integrate these individual design modules in a system level framework to design the transmission for given operating parameters, and (iii) use this framework to design a 100 HP, 93% efficiency, 32:1 speed ratio prototype for fabrication and testing under load. While the research focuses on development of Pericyclic transmission, the design framework is applicable to all high reduction, high power epicyclic gear systems. The presentation will lay special emphasis on design concepts that are in development in aviation industry for future jet engines, hybrid electric vertical take off and lift, and tiltrotor aircrafts. The author will also present his research plan and a wishful vision for establishing the center for power transmission and gearing research and development at IIT Kanpur to meet the critical needs of our aerospace, power generation, and transportation industries.

Bio-sketch:

Tanmay is currently employed at Leonardo helicopters (Philadelphia, USA) as drive system technical lead engineer. He is supporting the civil certification of a tiltrotor aircraft (AW 609) and research on torsional dynamics of multirotor powered lift aircraft drive systems. Prior to Leonardo helicopters, Tanmay worked as a Research engineer in the mechanical components and systems group at GE Research in Niskayuna, NY focusing on development of next. generation narrow body jet engine power gearbox. He earned his PhD and MS degrees in mechanical engineering from Penn State University while working at the Vertical Lift Research Center of Excellence (VLRCOE). He completed his B.Tech in mechanical engineering from IIT Roorkee in 2012.

Abstract:

This talk introduces a class of optimization problems - parameterized Sequential Decision Making (para-SDM) problems, and proposes a comprehensive framework to address them. Para-SDM problems cover a vast range of network logistics and planning problems that span diverse disciplines and applications such as facility location with path optimization (FLPO), vehicle routing, sensor network design, manufacturing process parameter optimization, last mile delivery, industrial robot-resource allocation, and data aggregation, classification, and clustering algorithms. These problems include large subclasses of problems such as Markov Decision Processes (MDPs), reinforcement learning (RL), clustering, resource allocation, scheduling, and routing problems. Conceptually, these problems require simultaneously determining the shortest path and allocating resources in a network, incorporating application-specific capacity and exclusion constraints, and while respecting the dynamical evolution of the network. This talk develops a flexible framework that addresses the class of optimization problems that fall under the ambit of para-SDM tasks.

Bio-sketch:

Amber Srivastava is currently a postdoc in the Automatic Control Laboratory at ETH Zürich. He obtained his PhD from the Department of Mechanical Science and Engineering at University of Illinois Urbana Champaign (UIUC), USA in August 2021. He received his Master of Science in Mathematics from UIUC in 2020, and his Bachelors of Technology in Mechanical Engineering from IIT-Kanpur in 2014. His areas of current research interests are Sequential Decision Making, Operations Research, Combinatorial optimization, Reinforcement Learning, Manufacturing process optimization , System Identification, and control systems. Beyond the academic work, Amber enjoys outdoor sports like cricket, badminton, and running.

Abstract:

Mediated by biological activity, emergent properties despite cell-level phenotypic noise shape microbial behaviour, physiology and community interactions. Yet, if (and how) cell-to-population scale emergence is regulated by biological activity has, to date, remained unexplored. This leaves a major gap in our understanding of microbial traits and strategies. Here, using quantitative microscale time lapse imaging, particle image velocimetry and a simple mathematical model, we capture the individual-to-population scale dynamics within sets of two distinct E. coli bacterial strains, growing independently under nutrient replete conditions. By tuning the growth temperature, we vary the cell-level biological activity and quantify its impact on the geometry, order and topology -- three key biophysical parameters -- which underpin the emergent dynamics in bacterial colonies. Our results reveal that temperature-mediated activity modulates the areal rate of colony proliferation and the dynamics of the mono-to-multi layer transition (MTMT). The MTMT cascades synchronous emergence of hydrodynamic fields, actively enhancing the micro-environmental transport. Furthermore, our experiments identify a strain-independent generalization of the dynamical microbial activity, synchronized with an equivalent topological phenomenon, that ultimately tunes the active hydrodynamics and microscale transport properties of the system. By harnessing temperature as a switch to control the geometric, structural and topological facets, we establish a mechanistic link between biological activity and emergent properties of growing bacterial colonies. Our results highlight how interplay of phenotypic noise triggers an emergent synchronicity across confluent systems.

Bio-sketch:

Jayabrata completed his Bachelors (B. Tech) from NIT Durgapur (Mechanical Engineering) in 2011. He graduated from the IIT Kharagpur with a Joint Masters-PhD Degree in 2017. His doctoral research focused on the dynamics of complex electrorheological (ER) fluids in micro-confinements. Specifically, he studied how electrical double layers can be used to activate and modulate the rheological complexity and flow structures of particulate (DER fluids) and homogeneous (liquid crystals) ER fluids in narrow conduits. Thereafter, Jayabrata joined the Geosciences Department at the University of Rennes 1 (DIMENV Group) as a postdoc to study the mechanism of carbon dioxide sequestration through a porous medium using experiments and numerics. Jayabrata moved to the Sengupta Lab in the Department of Physics and Materials Science, University of Luxembourg, in November 2019 as a HFSP Cross-Disciplinary fellow, where he used a combination of physical and biological approaches to decode the underlying physics of the transition of bacterial colonies to biofilms, and the ecology of bloom forming phytoplankton under nutrient stress conditions-observables common in a warming climate. Presently, he is working as a faculty in BITS Pilani, Hyderabad Campus, Department of Mechanical Engineering.

Abstract:

Microscopic quantum mechanical interactions among heat carrying lattice waves called phonons govern the macroscopic thermal properties of semiconductors. In this talk, I will describe how our newly developed first-principles computational framework to predict these microscopic interactions of phonons unveils a new paradigm for heat conduction in these materials. As an example, I will first describe a curious case of heat conduction in boron arsenide (BAs), where the lowest order interactions involving three phonons are unusually weak and higher-order scattering among four phonons affects the thermal conductivity significantly, in stark contrast with commonly-used semiconductors such as silicon, germanium and diamond [1]. I will demonstrate that, in fact, this large effect of four-phonon scattering on thermal conductivity is fairly common among compound semiconductors, driven largely by selection rules for phonon scattering processes [2, 3]. Next, I will show that these selection rules cause intricate competition among three and four phonon scattering processes, which can be exquisitely tuned to drive an unusual non-monotonic pressure dependence of the thermal conductivity in BAs and boron phosphide (BP), unlike in most other materials [4, 5]. Finally, I will show how boundary reflection and scattering of phonons affect the thermal conductivities of several materials in their thin film form. This last section of my talk will draw upon my prior experimental effort to probe the scattering of phonons at atomically rough surfaces of a nanoscale silicon film [6], and our on-going effort to study the effects of phonon mode conversion on the thermal conductivities of thin films made of compounds like indium phosphide, where the difference between the longitudinal and transverse lattice wave velocities is large.

References [*: Equal contribution]:
[1] Fei Tian, Bai Song, Xi Chen, Navaneetha K. Ravichandran et al., Science 361 (6402), 2018
[2] Navaneetha K. Ravichandran & David Broido, Phys. Rev. X, 10 (2), 021063, 2020
[3] Ke Chen*, Bai Song*, Navaneetha K. Ravichandran* et al., Science 367(6477), 2020
[4] Navaneetha K. Ravichandran & David Broido, Nature Communications 10 (827), 2019
[5] Navaneetha K. Ravichandran & David Broido, Nature Communications 12 (3473), 2021
[6] Navaneetha K. Ravichandran, Hang Zhang & Austin Minnich, Phys. Rev. X 8 (4), 041004, 2018

Bio-sketch:

Dr. Navaneetha K. Ravichandran is an assistant professor in the Mechanical Engineering department at IISc Bangalore. He is broadly interested in studying the thermal, thermodynamic and electronic properties of crystalline materials using non-contact optical experiments and predictive first-principles computation. Dr. Ravichandran obtained his Dual Degree (B. Tech and M. Tech) in Mechanical Engineering from IIT Madras. He obtained Masters in Space Engineering and Ph.D. in Mechanical Engineering from Caltech, working with Prof. Austin Minnich. For his Ph.D., Dr. Ravichandran worked on experimentally investigating boundary scattering of heat carrying lattice waves (phonons) in thin silicon membranes using the transient grating experiment. Subsequently, he was a postdoctoral research fellow at Boston College, where he worked with Prof. David Broido on developing a predictive first-principles computational framework to capture the thermal, thermodynamic and electronic properties of materials at high temperatures and extreme environmental conditions.

Abstract:

The interfacial phenomena revolve mainly around the evaporation of a sessile droplet on a solid surface and a droplet impact on a solid surface. The evaporation of a droplet containing colloidal particles is useful in many technical applications such as inkjet printing, manufacturing of bioassays, etc., and potential uses of the impact of liquid droplets on a microtextured surface are in designing self-cleaning and low drag surfaces. The present talk is on the coupled transport phenomena of these two problems. First, the impact dynamics of a microliter water droplet on a microgrooved surface are studied. The following impact outcomes are obtained as a function of the pitch and Weber number: no bouncing, droplet completely bounces off the surface, bouncing occurs with droplet breakup, or no bouncing because of a Cassie to Wenzel wetting transition. The present results on microgrooved surfaces are compared with published results on micropillared surfaces to assess the water-repelling properties of the two surfaces. Further, the pattern and profile of dried colloidal deposits formed after evaporation of a droplet on a non-heated and non-uniformly heated glass substrate are studied. On a non-heated substrate, the ring profiles are classified into discontinuous monolayer, continuous monolayer, and multiple layers ring on particles concentration-particle size plane. On a non-uniformly heated substrate, the dimensions of the ring formed on the hot and cold sides of the substrate are reported. In the case of smaller particle size, the contact line of the hot side depins, and together with twin asymmetric Marangoni recirculations, it results in a larger ring width on the cold side. In contrast, the contact line remains pinned for larger particles. The twin asymmetric Marangoni recirculations advect more particles on the hot side, resulting in a larger ring width on the hot side.

Bio-sketch:

Laxman Kumar Malla is a postdoctoral fellow in the Heat Transfer and Thermal Power Lab, Department of Mechanical Engineering at IIT Madras. He received his Ph.D. in 2020 from IITB-Monash Research Academy, a joint Ph.D. program between IIT Bombay, India, and Monash University, Australia. He completed his M.Tech in Thermal and Fluids Engineering from IIT Bhubaneswar in 2015 and B.Tech in Mechanical Engineering from Veer Surendra Sai University of Technology Burla in 2012. At IIT Madras, he is working on a sponsored project to improve the thermal performance of flat plate pulsating heat pipes (FPPHP) as an effective passive cooling device. In his Ph.D., he analyzed the profile and morphology of the colloidal deposits obtained after droplet evaporation and also studied various droplet impact outcomes on superhydrophobic microgrooved surfaces. His research area of interest is thermal management of devices, multiphase flows, droplet dynamics, and surface wettability. He has published his research work in 7 referred International journals and several conference papers. As a student, he received the Institute Silver Medal in the 4th Convocation, 2015 of IIT Bhubaneswar.

Abstract:

Present study deals with finite element (FE) formulation and analysis of a functionally graded (FG) shaft with transverse breathing crack(s) in a rotor-bearing system. The FG shaft is modelled using two-nodded Timoshenko beam with four DOFs per node. The FG materials are composed of Al2O3, ZrO2 and SS with the volume fraction of SS increasing towards the inner diameter of the shaft. Temperature dependent thermo-elastic material properties of the FG shafts are considered graded in the radial direction following power law of material gradation. Local flexibility coefficients are determined analytically as functions of size and orientation of crack, gradient index, and temperature using Castigliano’s theorem and Paris’s equations to compute the stiffness at any instant during the rotation of cracked FG shafts. Based on FE formulation, a MATLAB code has been developed for understanding the influences of shaft’s slenderness, material gradient index, temperature, relative size, location and orientation of cracks on the dynamic responses of the FG shaft system. Results show that the choice of gradient index has significant importance on natural whirling frequencies and critical speed for cracked FG shaft in the event of multiple transverse cracks appearing and it is possible to decide gradation parameter in damage tolerant design of such FG shafts. Results from stability analysis show that while the depths, orientations and locations of cracks and temperature gradient along with damping properties of materials affect the stability threshold speed, the choice of gradient index has significant importance on the threshold speed in the event of multiple transverse cracks surfacing on the FG shaft. Research outputs have been published in five referred journals, three book chapters and seven conferences proceedings.

Bio-sketch:

Dr. Debabrata Gayen born on 2nd March 1990 and lives in Sundarbans. He completed B.Tech in ME from Jalpaiguri Government Engineering College in 2011 and M.Tech in specialized of Machine design in ME from NIT Rourkela in 2013. He received his PhD degree from IIT Guwahati in 2019. He secured first division in all the examinations from class 10th onwards. As of now, he published research articles as a first author in 7 referred journals, 9 conference proceedings, 3 book chapters, and also presented 15 int. conferences and 1 national conference. He received 4 awards and recognition and also served as a reviewer at least 17 research articles in different noted int. journals. He has 21.5 months post PhD experience as an IPDF in Mechanical at IIT Bombay. His broad area of interest is Machine Design and Vibration, and his specific area of interest is ‘Design and Analysis of Functionally Graded Cracked Structures like Beams, Shafts, Rotors, Turbine Blades and Pipes’.

Abstract:

Constrained groove pressing (CGP) is one of the severe plastic deformation techniques to produce ultrafine-grained materials. The process involves repeated shear deformation using grooved and flat dies. In general, the die geometry of the process is decided based on the thickness of the sheet being deformed. The material characteristics, especially the ductility and strain hardening behavior affect the limit of deformation in the CGP process. Therefore, it is pertinent to incorporate the material parameters when designing the die for the CGP process. The commercial implementation of the CGP processed sheet is further limited due to the uneven surface produced during CGP. It is attempted to optimize the die geometry considering the material parameters so that the total plastic strain imparted during the process is increased.

Bio-sketch:

Dr. Sunil Kumar is an Assistant Professor in the Department of Mechanical Engineering at SVNIT Surat. Before joining here and after completing his Ph.D., he was working as guest faculty at NIT Jalandhar followed by NIT Hamirpur. He completed his Ph.D. in Metal Forming from IIT Delhi in 2019 and M. Tech. in Mechanical Design from IIT Madras in 2013. Before joining Ph.D., he also worked as an Assistant Professor in the School of Mechanical Engineering at LPU Jalandhar for two years. His research interest lies in Metal Forming, Material Mechanics, and Plasticity.

Abstract:

Reduced order models, both empirical and non-empirical, have the potential to better delineate the nature of aeroacoustic sound sources which could then be used to devise better control strategies. In this talk, we would consider a pair of identical interacting subsonic cold turbulent jets with an aim to explore the influence of jet shear layer interactions and the eventual breakdown of the resulting coherent structures, i.e. sound sources, into turbulence and their role on the spectral characteristics of the radiated far-field sound. The point of first interaction between the pair of jets is varied which models distinct physical configurations and thus different sources of sound. The turbulent near-field of the jets is computed using a large eddy simulation (LES), the acoustic far-field is obtained via the standard application of Lighthill’s acoustic analogy, while spectral proper orthogonal decompositions (SPOD) are used to construct non-empirical reduced-order models. In this seminar, I will be discussing our ongoing work in reduced-order models with a particular focus on twin-jet aeroacoustics.

Bio-sketch:

Arnab Samanta is an Associate Professor of Aerospace Engineering at IIT Kanpur since 2020. Prior to this he was a faculty in the Aerospace Engineering department at IISc Bangalore since 2011. He obtained a Ph.D in Theoretical & Applied Mechanics from the University of Illinois at Urbana-Champaign in 2009 with a thesis on modelling of the aeroacoustic scattering of vortical and acoustic waves at a diffuser exit. Next, as a Postdoctoral Scholar at Caltech, he developed non-linear reduced-order models for the sound sources from round and serrated turbulent jets. He was also involved in a collaboration with the NASA Jet Propulsion Laboratory (JPL) to model and simulate hot-air balloon aerobots for interplanetary explorations. In the recent past, he has been developing advanced lower-order models to analyse and control high-speed jets, reacting mixing layers, swirling flows, thermo-viscous flows, often supported by direct simulations and experiment

Abstract:

This talk will primarily dwell on an interesting class of essentially nonlinear oscillators, more specifically piecewise linear (PWL) oscillators. The dynamics of such oscillators are seemingly simple since they are linear in different domains of state space. However, PWL non-autonomous dynamical systems pose difficulties in analytical tractability of the transition (between domains) time instants. To this end, I will discuss some of the analytical methods that we have considered in analysing the dynamics of PWL Mathieu equation. Some of previous works have computationally explored the regions of parametric instability in the parametric space. In this work we introduce non-smooth basis functions and invoke the method of averaging to analytically describe the instability zones and show that it provides a good first order approximation of the boundaries of these instability zones. The second method that we consider is based on the canonical transformation to the Action-Angle variables, the method of averaging and the method of multiple scales to derive relatively simple analytical expressions for the transition curves corresponding to the 1: n resonances. In contrast to the classical Mathieu equation, its PWL counterpart possesses additional instability zones (e.g. for n > 2). In this study we demonstrate analytically the formation of these zones when passing from linear to PWL models as well as show the effect of the stiffness asymmetry parameter on their width in the limit of low amplitude parametric excitation. We show that using the analytical prediction devised in this study one can fully control the width of the resonance regions through the choice of asymmetry parameter. Unlike its linear and PWL counterparts, the PWL Mathieu equation with non-zero offset possesses transition regions which depend on initial conditions in addition to the amplitude and frequency of parametric excitation. Analytical study pursued in the present work reveals a special family of 1: n parametric resonance zones and completely depicts the mechanism of formation of the energy dependent transition regions.
The last part (if time permits) of the talk will dwell on the PWL dynamics of a cracked Euler-Bernoulli beam. The mode 1 crack in the beam is modelled as a PWL spring at the crack location resulting in slope discontinuity during the crack opening. The forced dynamics is studied considering the analytical methods discussed above to demonstrate their comparison with the semi-analytical approach and numerical simulations.

Bio-sketch:

K. R. Jayaprakash is working as an Assistant Professor in the Discipline of Mechanical Engineering at IIT Gandhinagar. He was a DST-INSPIRE Faculty in the Department of Aerospace Engineering, IISc Bangalore and Visiting Assistant Professor in the Department of Mechanical Engineering, IIT Kharagpur for a short stint. He completed his doctoral studies in Theoretical and Applied Mechanics from University of Illinois at Urbana Champaign in 2013. His doctoral study explored the nonlinear dynamics and acoustics of one dimensional granular media. He holds master’s degree in Mechanical Systems Dynamics and Control from IIT Kharagpur and bachelor’s degree in Mechanical Engineering from Visveswaraiah Technological University Bangalore. He has worked as Scientist/Engineer ‘SC’ for a couple of years in the Spacecraft Mechanisms Group at U R Rao Satellite Center (erstwhile ISRO Satellite Center) Bangalore. He was awarded the DST-INSPIRE faculty fellowship in 2013, GE-Foundation Scholar Leader in 2008 and DGFS fellowship (BARC) in 2007. His research interests include nonlinear dynamics and vibrations, structural dynamics, wave propagation in discrete lattices and continuous systems, dynamics of inflated structures, dynamics and acoustics of locally resonant structures, acoustic metamaterials.

Abstract:

I will provide an account of the interesting dynamics exhibited by droplets at multiple length and time scales in completely different domains namely gas turbines and COVID-19. In the first part of my talk, I will provide some insights into the dynamics of spray-swirl interaction with particular focus on droplet transport, breakup and dispersion. I will show how the fundamental insights gained through such interactions can be used to design new class of atomizers in gas turbines. In second part of my talk I will introduce how spread of COVID can be through respiratory droplets and fomites. In this part, I will provide a detailed exposition of how respiratory droplet dynamics can be mated with pandemic model to provide a first principle insights into infection spread rate. We will show through experiments using surrogate fluids, such models can be experimentally verified rigorously. Subsequently I will show how fomites form and how the virion are embedded in the crystal network using both contact free as well as sessile droplets. First part of the talk will focus on the inherent challenges and ambiguities involved in nonlinear modeling of soft active materials like MREs. Subsequently, the development of a coupled membrane theory starting from the 3D governing equations, will be presented. Finally, application of our theory to MRE membrane actuators of different geometries will be demonstrated.

Bio-sketch:

Dr. Saptarshi Basu is currently DRDO Chair Professor in the department of mechanical engineering at IISc. Prof. Basu primarily works on multiphase systems, especially droplets at multiple length and timescales across multiple application domains. He is a fellow of Indian National Academy of Engineering, ASME, Institute of Physics, Royal Aeronautical Society and Royal Society of Chemistry. Prof. Basu is the recipient of DST Swarnajayanti Fellowship in engineering.

Abstract:

Additive Manufacturing (AM) of metals is a promising advanced manufacturing technology capable of producing near net-shape industrial components. Central to the mechanics of the AM process is the relationship between the process parameters, the produced microstructure, the metallurgical changes, and the thermomechanical properties of the processed metal components. This presentation discusses the numerical techniques to simulate the complex process mechanics of metal AM. The effect of dynamic temperature cycles on the metallurgical phase transformations and generation of residual stresses, during deposition and post-deposition are presented. Additionally, relationship between AM specific grain microstructure, anisotropic material properties and process conditions for successful AM built are also discussed using a computationally efficient Discrete Dendrite Dynamics (DDD) model and mean field Crystal Plasticity based Finite Element (CPFE) theory. The results from numerical analysis are validated by experiments such as Neutron Diffraction for residual stress, EBSD for microstructures and Infrared camera measurements for melt pool dimensions. This research bridges the essential gap between multiscale (microstructure to part scale) analysis of metal AM processes. Importantly, the study highlights the importance of high energy beam modifications to achieve customized microstructure, mitigate residual stress distributions, overcome build failures, and redesign the metal AM system.

Bio-sketch:

Dr. Santanu Paul is currently a post-doctoral fellow at University of Pittsburgh. In 2018 he completed his doctorate from IIT Bombay, and Monash University. Before to this he did his Master’s in Thermal Engineering and B.Tech in Mechanical Eng. from IIT Delhi and NIT Surat.

Abstract:

With an eye to Industry 4.0, virtual process chain plays a significant role in industries to optimize residual stress as it affects the mechanical quality. This seminar addresses modelling challenges to simulate residual stress in two different products fabricated by compression molding: a thermoset based hybrid composite part and an optical glass lens. Time-domain viscoelastic homogenization is vital for process simulation and prediction of residual stress in hybrid composite parts. Effective material behavior predicted by transformational field analysis deviates significantly from actual behavior due to exclusion of field fluctuation. Incremental variational based homogenization implicitly considers local field fluctuations through second-order statistical moments. This method is applied here to a viscoelastic composite with Maxwellian phases. Two different bounds-based thermoelastic homogenization methods are coupled with the homogenization scheme. Results are then compared with the effective behavior of periodic configuration of particulate and unidirectional fibrous composite microstructures. Later local field statistics in a thermoelastic homogenization problem for a class of random microstructures are demonstrated and validated with full-field simulations. Meanwhile, residual stresses in the molded glass lens degrade its optical performance. Thermal boundary conditions (BC) affects the residual stress as well as the lens shape prediction. These BC’s includes glass-N2 interaction and glass-mold interactions. Thermal cycling of glass disc and lens molding experiments are performed to quantify these BCs. Computational study of the gas flow in the molding machine indicated an anomalous heat transfer mechanism during the cooling stage. In view of this mechanism, equivalent heat transfer coefficient values are obtained using residual birefringence data. This inverse approach is similarly used for lens molding experiments. A plotting scheme is developed around finite elements for computing birefringence to facilitate direct comparison with photoelastic measurements.

Bio-sketch:

Dr. Tarkes is currently a post-doctoral fellow at Institute of Engineering Mechanics, Karlsruhe Institute of Technology. In 2016 he completed his doctorate from Applied Mechanics, IIT Madras. Before to this he did his Master’s in Materials Science and Eng. and B.Tech in Mechanical Eng. His research interests are in the area of micromechanics and material modelling with application towards understanding residual stress formation in composite materials.

Abstract:

Soft active materials like magnetorheological elastomers (MRE) or electroactive polymers (EAPs) undergo large deformation in response to applied magnetic or electric field, thus enabling external field controlled soft actuation. These materials have the potential to be applied towards device design in the emerging field of soft robotics. In this seminar, I will be presenting our ongoing work on development of asymptotic continuum models for these materials. First part of the talk will focus on the inherent challenges and ambiguities involved in nonlinear modeling of soft active materials like MREs. Subsequently, the development of a coupled membrane theory starting from the 3D governing equations, will be presented. Finally, application of our theory to MRE membrane actuators of different geometries will be demonstrated.

Bio-sketch:

Prof. Santapuri is an Assistant Professor in the Department of Applied Mechanics at the Indian Institute of Technology Delhi since July 2016. Prior to joining IIT Delhi, Dr. Santapuri worked as a Visiting Scholar at the University of California, Berkeley and Assistant Professor at Polytechnic University of Puerto Rico. She received her PhD in Mechanical Engineering from The Ohio State University in 2013 and B.Tech from Indian Institute of Technology Madras in 2007. Her research is focused on mechanics of electro-magneto-elastic materials, soft active materials, and their applications to soft robotics, sensor and actuator devices, and energy harvesting. She has authored 17 international journal and conference publications, and two book chapters. She is also the recipient of Kusuma Young Faculty Incentive Fellowship at IIT Delhi, SERB-DST Early Career Researcher Award, NSF-EPSCoR Faculty Start-up Award and University Fellowship at The Ohio State University.

Abstract:

The Navier-Stokes equation is applied to calculate gas flows in the hydrodynamic regime when the intermolecular collisions predominate the gas-surface interaction. In the free molecular regime, the intermolecular collisions are neglected and the motion of every molecule can be considered independently on each other. In the transition regime, the molecular mean free path is comparable to a characteristic size of flow so that the Navier-Stokes equation is not valid anymore, while the intermolecular collisions are not negligible. In this regime, the kinetic Boltzmann equation is solved or the Direct Simulation Monte Carlo (DSMC) method is applied. In the presentation, a review of recent results on rarefied gas dynamics based on the DSMC method will be given with examples of their applications to practical problems in vacuum technology, in micro-systems, in aerothermodynamics, etc. More specifically, an importance of intermolecular potential and its influence on flow characteristics will be shown. Some information about the peculiarities of gaseous mixture flows will be also given.

Bio-sketch:

Prof. Felix Sharipov studied at the Moscow University of Physics and Technology, Faculty of Aerophysics and Space Research. He obtained his Ph.D. at the Ural State Technical University in Russia. In 1988, he joined the Physics Faculty of the Ural State University where he set up his activity in rarefied gas dynamics. In 1992, he moved to the Federal University of Parana in Brazil where he is currently Professor at the Physics Department. At this department, he built up a group on modelling of gas flows in microscale. His research interests are numerical and analytical methods of rarefied gas dynamics with applications to transport phenomena, microfludics, vacuum technology, aerothermodynamics etc. His group develops both probabilistic and deterministic approaches. The former represents the Monte Carlo methods, while the latter is based on the kinetic Boltzmann equation. Professor Felix Sharipov published more than 140 papers in peer-reviewed journals, two books and several chapters for handbooks. He was a guest editor of several special issues in “Vacuum” and currently he is a member of Editorial Board of this journal.

Abstract:

This talk will discuss the use vision-based methods for machine tool motion registration and modal analysis. Motion of three illustrative tools and one small machine were recorded using low- and high-speed cameras with sufficiently high resolutions. Pixels within images from recordings of the vibrating machine are treated as non-contact motion sensors. The tool’s own features are used to register motion using expanded image processing techniques. Motion estimated is governed by the method of motion registration, by the tool’s own features, by illumination conditions, noise, and the image acquisition parameters. Extracted motion was benchmarked against twice integrated tool point accelerations, and motion was generally observed to compare well. Since vision-based method are of the output-only type, methods to mass normalized eigenvectors will also be discussed. Modal parameters thus extracted from vision-based measurements and post-processed using mass-change methods were observed to agree with those extracted using more traditional experimental modal analysis procedures using a contact type accelerometer as the transducer. Methods discussed are generalized and can suitably be adapted for other applications of interest. For more on visual vibrometry.

Bio-sketch:

Dr. Mohit Law, who received his Ph.D. from the University of British Columbia, Canada, his MSc. from the Michigan Technological University, U.S.A., and his B.E. from Pune University, India. Dr. Law did his post-doctoral work at the Fraunhofer IWU in Germany. Dr. Law has previously worked as a machine tool designer.

Abstract:

Sloped terrain must be relaxed toward the horizontal terrain because the horizontal surface is gravitationally stable. On the Earth, erosion and weathering play a crucial role in the relaxation process. Particularly, existence of water and atmosphere significantly affects the relaxation. However, most of the planetary small bodies have neither atmosphere nor water. Therefore, relaxation process occurring on the surface of small bodies covered with regolith could be simply governed solely by typical granular dynamics. In this sense, asteroidal surface terrain should be explained by simple granular physics. For instance, slope relaxation due to the impact-induced seismicity and landslides due to the micro-meteorite impacts have been considered as possible mechanisms. Recently, we have performed a series of simple lab experiments that relate to the sloped terrain relaxation by vibration[1] and impact[2]. In this presentation, I will briefly review these experiments. In addition, we have recently developed the experimental apparatus that rotates a granular heap [3]. The rotated granular heap showed nontrivial relaxation process. Geometrical characterization of the rotated granular heap relates to the asteroidal top-shape formation. I will briefly introduce the result of this experiment as well.

Bio-sketch:

Prof. Katsuragi is currently working as a faculty in the Department of Earth and Space Science, Osaka University. Prior to this, Prof. Katsuragi has worked as an Associate Professor (2011-20) at the Nagoya University and as a Research Associate at Kyushu University (2001-11). He completed his B.Sc. (Earth and Planetary Sciences) and M.Eng. (Applied Physics) from Kyushu University, Japan in 1996 and 1998 respectively. Prof. Katsuragi received his Dr. Sc. from Kyushu University in 2004. His research is focussed in the area of Soft-matter, Earth and Planetary-physics mainly studied by various experiments.

Abstract:

Microscopic quantum mechanical interactions among heat carriers called phonons govern the macroscopic thermal properties of semiconductors. In this talk, I will describe how our newly developed first-principles computational framework to predict these microscopic interactions of phonons unveils a new paradigm for heat conduction in these materials. As an example, I will first describe a curious case of heat conduction in boron arsenide (BAs), where the lowest order interactions involving three phonons are unusually weak and higher-order scattering among four phonons affects the thermal conductivity significantly, in stark contrast with commonly-used semiconductors such as silicon, germanium and diamond [1]. I will demonstrate that, in fact, this large effect of four-phonon scattering on thermal conductivity is fairly common among compound semiconductors, driven largely by selection rules for phonon scattering processes [2]. Next, I will show that these selection rules cause intricate competition among three and four phonon scattering processes, which can be exquisitely tuned to drive an unusual non-monotonic pressure dependence of the thermal conductivity in BAs and BP, unlike in most other materials [3, 4]. Finally, I will demonstrate the capability of our unified framework in capturing other phonon scattering processes, such as those caused by isotopic impurities, which resulted in the experimental realization of a giant isotope effect on the thermal conductivity of cubic Boron Nitride [5]. If time permits, I will also briefly describe my prior experimental effort to probe the scattering of phonons at atomically rough surfaces of a nanoscale silicon film, where they showed extreme sensitivity to the changes in surface roughness of just a few atomic planes [6].

Bio-sketch:

Dr. Navaneeth K. Ravichandran is an assistant professor in the Mechanical Engineering department at IISc Bangalore. He is broadly interested in studying the thermal, thermodynamic and electronic properties of crystalline materials using non-contact optical experiments and predictive first-principles computation. Dr. Ravichandran obtained his Dual Degree (B. Tech and M. Tech) in Mechanical Engineering from IIT Madras. He obtained Masters in Space Engineering and Ph.D. in Mechanical Engineering from Caltech, working with Prof. Austin Minnich. For Ph.D., Dr. Ravichandran worked on experimentally investigating boundary scattering of heat carriers (phonons) in thin silicon membranes using the transient grating experiment. Subsequently, he was postdoctoral research fellow at Boston College, where he worked with Prof. David Broido on developing a predictive first-principles computational framework to capture the thermal, thermodynamic and electronic properties of materials at high temperatures and extreme environmental conditions.

Abstract:

Immersed Boundary Method (IBM) was first introduced by Peskin (1972) for simulation of cardio-vascular flow within the oscillating heart geometry using a Cartesian mesh framework. Since then this method has been extensively used in simulation of flow involving complex, moving geometries as well as fluid-structure interaction problems. IBM retains the simplicity of regular Cartesian/curvilinear mesh which does not necessarily conform to the boundary of the flow domain. The boundary conditions are replaced by adding appropriate forcing terms in the governing equations. Although, good agreements with experimental data are reported, some of the critical issues like improper mass conservation and spurious pressure fluctuation are still not well-addressed. Approaches like cut-cell methods, mass source/sink addition to immersed cells have been reported to vent this problem. However, these methods have been of limited use and applicability due to complexity in formulation and ill-conditioning of the solution matrices. The present talk introduces of a mass conserving IBM methodology which results into a better control over pressure fluctuations for moving boundaries. This talk further discusses about the computational overheads in IBM and implementation of GPU-based parallelization schemes to address that. The proposed methodology is demonstrated over a range of flow problems involving mixing, heat transfer, arterial flow and aerodynamic applications.

Bio-sketch:

Dr. Somnath Roy is currently an Associate Professor in the Department of Mechanical Engineering jointly with Centre for Computational and Data Sciences at Indian Institute of Technology Kharagpur. He completed his B.E. from Jadavpur University, M. Tech. from IIT Kanpur and PhD from Louisiana State University. He worked as a Research Associate and Visiting Faculty at Louisiana State University and then joined IIT Patna on February, 2011. In 2016, he moved to IIT Kharagpur. His research interest involves Computational Fluid Dynamics, Mixing, Heat Transfer, Turbulence, Micro-Air Vehicles, Biofluidics and High Performance Computing. He is PI for the NSM nodal centre for training in HPC and AI at IIT Kharagpur.

Abstract:

Many real-world technologies employ an airfoil that is wall-mounted and finite in length with boundary layer impingement at the airfoil-wall junction and flow over the tip. Examples include submarine hydrofoils mounted to a hull, wind turbine blades mounted to a hub or the stators in an aeroengine that are connected to an outer wall. An important aspect of airfoil noise production that has received little attention in the past is the influence of airfoil three-dimensionality and end-effects, which is the focus of this seminar. Recent results will be presented from a series of airfoil flow and noise measurement campaigns conducted in different anechoic wind tunnel facilities. A combination of acoustic array measurements, flow visualizations, surface pressure and unsteady wake data are used to gain insight into the turbulent noise sources and the role of three-dimensional vortex flow near the airfoil tip and wall junction in noise production.

Bio-sketch:

Danielle Moreau obtained her PhD from the University of Adelaide in 2010. Following PhD completion, she worked as a research associate at the University of Adelaide for five years where she investigated the mechanics of bio-inspired quiet airfoils and submarine hydrofoil noise generation. In 2015, Danielle moved to UNSW Sydney where she currently holds the position of senior lecturer. Her research focuses on the understanding and control of flow-induced noise with the aim of quietening modern technologies. Her major research contributions have been in (i) wall-mounted finite airfoil aeroacoustics, (ii) airfoil trailing edge noise production and control, (iii) rotor, fan and wind turbine noise generation and (iv) bluff body flow noise.

Abstract:

When two nominally flat surfaces are brought close to each other, contact is established at multiple points due to multiscale roughness. Tribological properties like friction and wear depend on the size, distribution and interaction of these local contact regions called asperities. The interplay between geometry, material property and mechanics determine the behaviour of asperities. Macroscopic property emerges as the evolution of the interaction at the multiple asperities. To understand this emergence, we systematically study the mechanical behaviour of multi asperity contacts for different asperity geometries and materials. Materials behave differently at small scales due to various defects. To isolate the scale effect, either the scale can be increased, or asperities can be made of ordered, identical geometry. We create asperities of sub-millimetre to submicron scales. We exploit ordered nanostructures of anodised alumina to create asperities at small scales. Going down the scale further, we have stumbled upon hydrogels which enables manipulation of the molecular geometry to control material properties. In this talk, some of the interesting observations on contact mechanics in these two systems will be discussed.

Bio-sketch:

Prof. M.S. Bobji is a faculty member in the Department of Mechanical Engineering, IISc. Bangalore. Post his PhD in 1999 from IISc Bangalore, Prof. Bobji worked at the Ohio State University (1999-200) and the University of Oxford (2000-03) as a postdoctoral research fellow. His research activities are primarily focused towards understanding the evolution of macroscopic behaviour of contact between two surfaces from the microscopic properties of the materials. The insights gained is used to develop various application in a variety of interrelated areas. His research group has been actively involved in the development of many tools and techniques such as in-situ tribometer, needle-tissue interaction tester, ice adhesion test rig etc.

Abstract:

A systematic approach is developed to explicitly quantify the combined effects of anisotropic deformation behavior of grains and grain boundaries on the fracture of polycrystalline metals. A cohesive finite element (CFEM) based multiscale computational framework is employed to predict the fracture properties such as KIC and JIC of polycrystalline metals as functions of microstructural attributes. The focus is on characterizing the effects of grain boundary misorientation distribution, crystallographic texture, and the grain size distribution on fracture toughness. The framework uses computationally generated statistically equivalent microstructure sample sets allowing statistical variations and distributions of the fracture behavior due to microstructural variabilities and the influences of intergranular and transgranular fracture mechanisms to be quantified and analyzed. A crystal plasticity formulation is used to model the anisotropic deformation in the grains. A misorientation-dependent interfacial relation is used to model orientation-sensitive crack growth through grains and grain boundaries. Calculations carried out for Mo under 2D and 2.5D plane strain conditions capture and delineate the competing effects between (a) intergranular and transgranular fracture and (b) plasticity and crack growth on the overall fracture toughness of the material. The results indicate that, as the fraction of grains with preferred orientation increases, grain size increases, and the inhomogeneity in grain boundary behavior decreases, transgranular fracture dominates relative to intergranular fracture. Consequently, the relative contribution of dissipation associated with a transgranular fracture is enhanced, resulting in higher overall fracture toughness for the material analyzed. The trends are characterized and quantified in terms of the effective grain size distribution, fraction of grains with favorably oriented slip systems, and misorientation-dependent GB characteristics. Although the calculations shown are performed on bcc Mo, the approach can be applied to other material systems. In summary, the aim of this presentation is twofold, first to provide a brief overview of my research activities in the field of mechanics of materials, and then to share our efforts in understanding the complex microstructural effects on macro-scale fracture behavior of polycrystalline metals and how this work opens myriads of research opportunities for future.

Bio-sketch:

Ushasi Roy was a Research Associate in the Department of Engineering, the University of Cambridge from January 2020 to February 2021. In June 2021, she will be joining Prof. Christopher Schuh’s research group at the Massachusetts Institute of Technology (MIT) to study the dynamic deformation behavior and jetting at the metal particle/substrate contact under single particle impact. As a postdoctoral researcher at the University of Cambridge, she studied the mechanics of void growth in solid-state Li-ion batteries with Prof. Norman Fleck and Prof. Vikram Deshpande. Prior to that, she completed her Ph.D. in Mechanical Engineering from the Georgia Institute of Technology (Georgia Tech) under the supervision of Prof. Min Zhou in December 2019. For her Ph.D. dissertation, she worked on the development of a microstructure-sensitive multiscale computational model to simulate fracture as a function of microstructural attributes in polycrystalline metals. Also, during her Ph.D., she developed mesoscale models of energetic composites in 2D and 3D to study the effect of microstructure on their hotspot dynamics under impact loading. Before joining Georgia Tech in August 2015, she worked as a Researcher in the Coated Products (CP) research group of Tata Steel Research and Development in Jamshedpur from June 2013-August 2015. She earned her master’s degree in Metallurgical Engineering from IIT Kharagpur in 2013 and her bachelor’s degree in the same discipline from Jadavpur University in 2011. For her master’s thesis, she worked on the evaluation of fracture toughness and fracture micromechanisms in high entropy alloys under the supervision of Prof. K. K. Ray. Her research interests lie broadly in the fields of mechanics of materials, fracture mechanics, microstructure-sensitive modeling of mesoscale deformation behavior, crystal plasticity, and finite element modeling.

All interested are welcome to join via the zoom link.

Abstract:

This seminar will explore a scalable computational mechanics architecture developed, called Hydro-UQ, aimed at HPC and the next-generation exascale systems. In particular, the seminar will focus on the contact mechanics formulations developed. Hydro-UQ architecture is used to study (a) fluid-loading on solids (b) fluid-driven contact between solids. These solid bodies are generally restrained structures (buildings, bridges, off-shore structures), semi-restrained structures (ships in the harbor), unrestrained structures (ships, submarines in sea), geological materials (sediment transport). Such loading scenarios are commonly encountered during water-borne natural hazards like tsunami/floods. This scalable architecture has potential applications ranging from identifying the extent of oil spill scenarios to the distribution of non-exhaust emission particulates, and many more. The seminar will conclude with a brief overview of other research areas that are also concurrently being addressed, namely concurrent multiscale modeling of materials, automatic differentiation, and data-driven engineering.

Bio-sketch:

Dr. Ajay B. Harish is presently a postdoc with Prof. Sanjay Govindjee at the Department of Civil and Environmental Engineering at the University of California, Berkeley. Additionally, he is also associated with the SimCenter of Natural Hazards Engineering Research Infrastructure (NHERI). His expertise lies in the multi-disciplinary area of scalable computational continuum mechanics. At the SimCenter, he develops HPC applications for climate modeling and aimed for usage on the present Peta- and upcoming exascale computing architectures. He was one of the seven worldwide finalists of the 2015 Robert J Melosh medal competition; he was awarded the best student & best student in Mechanics award by the Leibniz Foundation in 2016 & 2017. Before he arrived at UC Berkeley, he was awarded a Doctoral degree (with Honors), under the guidance of Prof. Peter Wriggers, in Mechanical Engineering at Leibniz University Hannover (Germany); a Masters in Aeronautics from California Institute of Technology (USA) and a Bachelors in Mechanical Engineering from National Institute of Technology Karnataka (India).

All interested are welcome to join via the zoom link.

Abstract:

Introduction of magnetism in an electrochemical system opens new horizons to explore the possibilities of high-performance lithium-ion batteries (LIBs) during fast charging. Graphite is the most widely used commercial anode material due to its low potential window and high electrochemical reversibility. However, the rate-limiting diffusion characteristic and catalytic surface behavior of graphite anodes towards electrolytes cause the onset and propagation of degradation mechanisms like SEI formation, and more severely, lithium plating and interfacial fracture, in LIBs under extreme operating conditions.
This seminar will be focused on the impact of magnetism on electrochemical performance of fast charging LIBs (Fig.1a). The first half of the seminar will discuss a coupled computational-experimental approach to deconvolute the synergistic evolution of interfacial degradation mechanisms. The film evolution on the anode surface over multiple fast charging (1 – 6 C) cycle is probed using in-situ electrochemical (cycling, DCR, EIS) and post-mortem (SEM, EDS, XPS) characterization. Two interesting observations are made on the kinetic exchange between SEI growth and lithium plating. First, a suppression in lithium plating over multiple cycles at high C-rates (> 2C). In addition, strain induced film crack nucleation (4C) and propagation (5C) is observed. A computational model demonstrates exchange interactions between lithium stripping, irreversible SEI formation and film fracture. Second, a depreciation in capacity loss at ultra-high C-rates (> 5C), with no indication of crack formation.
The second half of the seminar will discuss the effect of external magnetic field on ionic transport. The inhomogeneous lithium ion transport though the convoluted diffusion pathways of the electrode and separator causes the evolution of the degradation mechanisms. The application of magnetic field results in flux homogenization due to magnetohydrodynamic forces (MHD) on transversely diffusing ions. In-situ electrochemical measurements indicate a depreciation in capacity fade with the application of magnetic field (Fig. 1b). Post-mortem characterization reveal a reduction in dendritic lithium growth and a complete suppression in film fracture. A maximum capacity gain of 23% is obtained from lithium cobalt oxide/graphite (20mAh) pouch cells at 5C with an applied field of 1.8kG. A parametric study of field strength study indicate a saturation effect on the capacity gain beyond 2kG, thereby, limiting the magnetic field requirement at high C-rates.
The seminar will conclude with a glimpse of preliminary investigations in magnetically orientable anodes, for example, functionalized laser-induced graphene from polymeric sheets, for designing of low tortuosity and energy dense LIBs.

Bio-sketch:

Abhishek Sarkar earned his B.Tech with gold medal in Mechanical Engineering (ME) in 2015 from Delhi Technological University. He joined Iowa State University as graduate student in ME, where he consecutively finished his MS in 2017 and PhD in 2018. His master’s thesis was on thermo-mechanical analysis and material selection of lithium battery electrodes. During, his PhD he joined Ames Laboratory, a federal laboratory under the US Department of Energy. His PhD research involved computational multiphysics modeling of mechano-thermo-chemical response of lithium batteries and electromagnetic performance of electric drives. Upon completion of his PhD, he joined Ames Laboratory as a Postdoctoral Research Associate in 2019. He was involved in the development of additively manufactured magnetic materials with functionalized magnetic alignment. Since 2020, Abhishek has majorly contributed in the development of a lithium battery characterization and recycling facility in Ames Lab. Abhishek has 11 published (10 first author) publications in peer-reviewed high impact journals and 2 pending patent applications, and written over 6 project proposals (2 accepted and 4 under review).

All interested are welcome to join via the zoom link.

Abstract:

Dr. Shantanu Shahane will give a brief overview of the past and current research work including his master's, doctoral and postdoctoral work. He will go into details of his current research: meshless methods. He has been developing the meshless method, also known as the generalized finite difference method for the solution of partial differential equations (PDEs). Radial basis functions (RBFs) are used to estimate derivative operators in the PDE on a point cloud. Polyharmonic spline as RBF with appended polynomials has shown exponential convergence with increasing polynomial degree. Hence, this approach is capable of giving higher-order accuracy without any additional algorithmic and code development. Moreover, since this method does not require underlying grid connectivity, adaptive mesh refinement can be easily implemented. He will show the application of this method to the solution of fluid flow problems. He will conclude with the potential of his current research and how it can be used in the future to improve the efficiency and accuracy of process modeling.

Bio-sketch:

Dr. Shantanu Shahane is currently a postdoctoral research associate at the University of Illinois at Urbana-Champaign (UIUC), USA. He completed his bachelor's and master's (dual degree) from IIT Bombay in 2015. He worked with Prof. Sanjay Pande at IITB to model wire electro-discharge machining for his master's dissertation. He started his Ph.D. at UIUC in August 2015 under the guidance of Prof. Surya Pratap Vanka. Profs. Shiv Kapoor, Narayana Aluru, and Placid Ferreira were his co-advisors. For his doctoral dissertation, he worked on numerical modeling of solidification and heat transfer during die casting together with uncertainty quantification, machine learning, and design optimization. Since Aug 2019, he has been a postdoctoral associate at UIUC. His latest areas of interest include meshless methods for the solution of partial differential equations, scientific machine learning, and optimization.

All interested are welcome to join via the zoom link.

Abstract:

Currently, mechanical micromachining is rapidly gaining wide acceptability in the production of micro-feature-based industrial components such as microfluidics, fiber optics products, printed circuit boards, fuel injection nozzles, filters, cooling channels in turbine blades, etc. It has advantageous properties such as high material removal rate and ability to machine most of the engineering materials like ferrous alloys, nonferrous alloys, plastics, ceramics, and composites. However, downscaling effects of mechanical micromachining cause higher specific cutting energy, dynamic instability, accelerated tool wear, and deteriorated surface quality. Therefore, modeling and analysis of mechanical micromachining considering the downscaling effects are essential to understand the cutting mechanism and to select the cutting parameters for process performance enhancement. In this talk, new concepts and contributions on the modeling and analysis of micro-drilling and micro-milling considering minimum chip thickness, tool run out, tool edge radius effects, multi-phase structural effects and tool dynamics are discussed. Mechanical micromachining processes are then applied to fabricate micro-textures on the surfaces of an important bio-implant material, Ti-6Al-4V. Wettability and bio-tribology performances of textured surfaces under in vitro condition of hip joint prosthesis are analyzed for different texture parameters. The micro-grid structure obtained with micro ball-end milling is found to provide enhanced performance due to its hemispherical end and unique pyramidal structure. This talk further includes the contributions on the analysis of micro-slot grinding of glass. Texturing on the PCD tool surface and the performance enhancement due to textured micro-grinding tools are discussed. This talk is concluded with brief discussions on the characterization of soft polymers using in-house developed biaxial testing device, cryogenic mechanical micromachining of soft polymers for wearable device applications and future research directions in mechanical micromachining.

Bio-sketch:

Dr. Karali Patra is an Associate Professor in the Department of Mechanical Engineering, Indian Institute of Technology Patna (IIT Patna), Patna, India. He did his B.E, MTech and PhD in Mechanical Engineering from BE College, Shibpur (now IIEST, Shibpur), IIT Guwahati and IIT Kharagpur, respectively. He worked as research associate at Robotics Research Center, Nanyang Technological University in 2007-08 before joining IIT Patna in December, 2008. His current research interests are analysis of mechanical micromachining processes for difficult to machine materials and development of smart materials based sensors, actuators and energy harvesting systems. He has collaborated with eminent researchers from Canada, UK, Germany, Hungary, Russia and Singapore through various exchange programmes and joint international projects. He has guided 6 PhD theses and 16 MTech projects so far. His research has resulted in 3 prototypes (cryogenic micromachining chamber, hand prosthesis and biaxial testing device), 10 patent applications (one granted), 52 international journal papers and 55 conference papers.

All interested are welcome to join via the zoom link.

Abstract:

Fusion welding of Aluminum (Al) to Titanium (Ti) is a challenge due to the large difference in their physical and thermal properties, especially their melting points. Friction Stir Welding (FSW), which is a solid-state welding technique, has proposed as a solution to this problem. However, there are inherent problems even during the FSW of Ti and Al. The present investigation is an attempt to solve those problems.
In the present experiments, FSW of commercially pure Al and commercially pure Ti is carried out with and without inserting a thin sheet of metal as an interlayer, such as Zinc (Zn) and Niobium (Nb). The choice of interlayer materials in this study is based on their solid solubility with Al and/or Ti, and their melting temperatures. Since process parameters used during FSW play an important role in microstructural evolution and mechanical properties of the weld, parameters have been optimized following the bottom-up approach.
The distribution of phases after welding has been characterized by X-ray tomography. The result shows that the weld nugget contains Ti particles that vary in size throughout the weld nugget. The Ti particles are inhomogeneously distributed in the weld nugget and their distribution depends on their morphology. The microstructure of both Al and Ti appears to be substantially refined and recrystallized, as revealed by Scanning Electron Microscopy (SEM) - Electron Backscatter Diffraction (EBSD). The failure of the tensile sample occurs in the Al side of the weld. The fractograph indicates both ductile and brittle modes of fracture. The microstructure of the weld nugget has been found to be stable at a higher temperature.
The deformation of Ti at low temperature and high strain rate by Adiabatic Shear Banding (ASB), wherein very fine grains are observed. Microstructural evolution in Al is gradual due to high Stacking Fault Energy (SFE), which leads to Continuous Dynamic Recrystallization (CDRX) through Dynamic Recovery (DRV) mechanism. The intermetallic compounds and mechanical mixing influences the stability of the microstructure in the weld nugget. Proper control of Ti particles' distribution by optimizing the process parameters can lead to superior mechanical properties and high-temperature microstructural stability of the weld nugget. It is possible to use this method to produce composites with unique properties and structural components used in the aviation industry.
With this understanding, FSW of Al to steel (Fe) has been performed using an adjustable tool to reduce the heat input and tool wear, and increase the mechanical deformation during welding. In addition to those, I will give brief information about my additional research works on incremental sheet metal forming, friction stir processing, friction stir deposition, accumulative roll bonding, hybrid manufacturing of dissimilar materials. Each of the processes has been investigated to elucidate the structure-property correlation and understanding the micro-mechanism associated with severe thermo-mechanical processing.

Bio-sketch:

Dr. Amlan Kar is a faculty member in the Department of Mechanical Engineering, IIT (ISM) Dhanbad, India. He did his B.Tech. at Jalpaiguri Government Engineering College, and subsequently joined IIT Madras’s M.Tech program in metal forming specialization, in the Department of Metallurgical and Materials Engineering. He joined the Indian Institute of Science (IISc) Bangalore, Bengaluru, India, for his Ph.D. on dissimilar Friction Stir Welding. He worked on multiple industrially relevant projects such as “Incremental sheet metal forming of titanium”, “Development of composite using Friction Stir Processing”, “Development of Friction Stir Welding Technique for Joining Dissimilar Light Alloys” and Dissimilar Friction Stir Lap Welding of Aluminum to Steel using an Adjustable tool at JWRI, Osaka University. Currently, he is working on different dissimilar welding techniques, mechanical joining, additive manufacturing, accumulative roll bonding, hybrid manufacturing, cold spray technology, friction stir welding, sheet metal forming, self-pierce riveting, and friction stir deposition for repairing work. The primary objective of all these research activities is to improve the mechanical properties at a wide range of temperatures using the concept associated with the mechanical behavior of materials.

Abstract:

Secondary manufacturing such as machining and joining is required to develop products with intricate shapes. The conventional machining operations like drilling, milling, trimming, etc. which are frequently performed for making composite parts are not convenient anymore because of a plethora of challenges encountered. The damage formed in and around the machined features creates an uneven surface which subsequently results in poor surface quality or rejection of the composite part. Also, joining of polymer composite is not an easy task due to the anisotropic and inhomogeneous nature of composites. Inadequate joint strength may lead to premature failure of the component due to high-stress concentration. Therefore, the study of both machining and joining behavior of composites is necessary to improve the life span of the product. The machining and joining behavior of the fiber-reinforced composites has been experimentally investigated. Both conventional and non-conventional machining methods have been applied to improve the quality of the machined features. Different joining methods namely mechanical joining, adhesive joining, hybrid joining, ultrasonic welding, friction stir welding, and resistance welding have been investigated to find the suitable joining technique. The effects of different machining and joining parameters have also been studied by investigating the quality of the machined surface and failure behavior of the joints.

Bio-sketch:

Dr. Debnath completed his bachelor's and master's degree in Mechanical Engineering from NIT’s. He completed his Ph.D. from IIT Roorkee in 2015 field of manufacturing of composite materials. He started his career as an Assistant Professor in the Department of Mechanical Engineering of NIT Meghalaya in 2015. He has published more than 80 technical manuscripts in peer-reviewed journals and proceedings, and 23 technical manuscripts that have been included as chapters in books published by internationally renowned publishers namely Elsevier, Springer, Wiley, Woodhead, CRC Press, etc. He has also edited one book titled ‘Primary and Secondary Manufacturing of Polymer Matrix Composites’ published by CRC Press and field an Indian Patent. He is currently supervising 7 Ph.D. scholars and supervised 2 Ph.D. theses in the area of processing and characterization of composite materials. His current research is focused is in the area of conceptualization and development of bio-degradable composites and manufacturing methods. He was honored with the prestigious ‘Excellent Research Contribution Award’ on the occasion of Institute Day of NIT Meghalaya. He has received several recognitions for his research contribution namely “Excellent Oral Presentation Award” in 10th ICCM held in Thailand in 2019, Best Paper Award” in CIMS held at NIT Jalandhar, India in 2020, “Excellence Award (Rank 1)” in 40th MATADOR held in China in 2019, and “Best Paper Award” in ICRIME held in Ludhiana, India in 2013.

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Abstract:

A significant challenge in the development of a hypersonic vehicle that is yet to be overcome is the design of a supersonic combustor that can operate for longer durations of time. The design of the supersonic combustor is itself made challenging by the fact that the fuel injected into a high-speed freestream has to spread and mix and burn within a short distance of about 1 m. In the case of liquid fuel, in addition, the fuel must also evaporate. Since supersonic combustion is predominantly mixing controlled, many research works have focused on improving the mixing through (a) different injection strategies -- transverse (normal) and angled wall injection and injection from struts or other structures placed in the middle of the combustor and (b) injection using injectors of different shapes -- circular, elliptical, polygonal and others. The latter aspect, namely, the effect of injector port shape on the mixing and spreading of gaseous fuels, is of relevance to the present study. One important aspect that has not been investigated in the earlier studies is the effect of the flow field within the injector itself. The Mach number at the exit of the injector has been assumed to be unity (sonic injection) in all the previous studies, thereby obviating the need to study the flow field inside the injector. In a recent study, it is shown that the Mach number at the exit of the injector is actually supersonic even in the case of constant cross-sectional area injectors, on account of the sudden, large area reduction from the injector plenum chamber to the injector passage and the formation of an aerodynamic second throat due to flow separation. The impact of the injector flow field, at design and off-design operating conditions is investigated numerically in the present study.

Bio-sketch:

Dr. V. Babu is currently a Professor in the Department of Mechanical Eng at the Indian Institute of Technology Madras, India. He obtained his BE in Mechanical engineering from REC Trichy in 1985. He received his MS and Ph.D. from the Ohio State University in 1989 and 1991 respectively. He was a Post-doctoral Researcher at the Ohio State University from 1991-1995. During this time, he developed computer programs for simulating the flow of plasma through arc jet thrusters with the ultimate objective of evaluating the frozen flow losses. From 1995-1998, he worked at the Ford Scientific Research Lab, as a Technical Specialist. During this time, he worked on vehicle exterior aerodynamics and aeroacoustics. He, along with his team members, Gary Strumolo, Robert Lietz, and Jian Pan was awarded the Henry Ford Technical Award for the design, development, and deployment of the Virtual Aerodynamic/Aeroacoustic Wind Tunnel. He has 5 US patents to his credit. Dr. Babu moved to India in 1998 and joined the Indian Institute of Technology Madras. His research interests are Modelling of high speed reacting flows, Supersonic combustion, Prediction of noise from subsonic jets with and without nozzle trailing edge modifications, Simulation of flows using the lattice Boltzmann method, and High-performance computing.

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Abstract:

Lithography-based micromachining processes have primarily evolved for silicon processing for semiconductor industries. These processes have some inherent limitations in work materials and feature geometry. In contrast, subtractive machining can create 3-D free-form features in a wide range of engineering materials. However, scaling down the subtractive process to a micro-scale is extremely challenging due to the limited flexural strength/stiffness of the micro-tool. Catastrophic tool failure due to cutting forces is the major impediment in subtractive micromachining. To address these issues, two approaches can be used: laser-induced local thermal softening or ultra- highspeed machining (>100,000 rpm) to reduce the cutting forces. Note that the high-speeds and low flexural stiffness can make the process susceptible to dynamic instability. In addition, additive manufacturing at the micro/mesoscale for restoration has immense potential. However, laser direct energy deposition-based repair poses unique technological and scientific challenges with respect to residual stresses due to complex thermomechanical behavior and metallurgical transformations, dynamic melt-pool spreading, and mass transfer due to thermocapillary effect. Addressing, these issues could potentially open novel ways of materials processing at micro/mesoscale.

Bio-sketch:

Prof. Ramesh Singh is a Professor at IIT Bombay. His research interests are laser additive manufacturing, ultra-highspeed micromachining, super-finishing, and finite element simulation of manufacturing processes. He is actively involved in the design and development of special-purpose machines for the Indian industry and the strategic sector. He has a very active association with Indian Industry, such as Ceat Tyres, Axis Microtools, PCI, KGK Diamonds, Bharat Forge, L&T, NTPC, etc. He received his Ph.D. from Georgia Institute of Technology, MS from Tufts University, and Bachelors from Birla Institute of Technology, Ranchi. He has published more than 180 international journals and peer-reviewed conference publications. He has been awarded 2 Indian and 1 US patents and filed 2 Indian and I US patents. He has guided 16 PhDs and over 70 Masters students. He has received the prestigious Swarnajayanti Fellowship from the Department of Science and Technology in Engineering Sciences in 2015 and the North American Manufacturing Research Institute outstanding paper award at 44th NAMRC at Virginia Tech in 2016. He is the Associate Editor of the Transactions of Institution of Industrial and Systems Engineers and serves on the Editorial Board of Nature Scientific Reports, JMST Advances, and International Journal of Precision Technology.

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Abstract:

Many self-propelling or active particles, such as motile microorganisms and phoretic swimmers, move through surrounding fluid media. The particles together with the ambient fluid form an active suspension. Self-propulsion of the particles drives the system arbitrarily far from thermal equilibrium and sets up non-trivial active flows, resulting in a wide range of rich and surprising phenomena. In this talk, I shall discuss a few complex aspects of the self-propulsion of E. coli, a bacterium widely used as a prototype for a living active particle in a suspension. Subsequently, I shall discuss how the propulsion dynamics at the individual level leads to dramatic consequences on the properties of mesophases formed by a large number of active particles. I shall summarize by describing our current approach that starts from a simplified model of an individual microswimmer and aims to bridge the realms of the individual and collective dynamics.

Bio-sketch:

Dr. Tapan Chandra did his M.Sc. from IIT Guwahati and Ph.D. from IISc., Bengaluru. After that, he completed two postdoctoral fellowships at the Technical University, Berlin and Johannes Gutenberg University, Mainz, respectively. Subsequently, for a short period, he joined the Max Planck Institute for Polymer Research, Mainz for another postdoctoral stint, before joining his current position at IISER Tirupati in 2019 as an Assistant Professor of Physics. He is interested in the broad research areas of Active Matter, Nonequilibrium Statistical Physics, Driven Soft Matter, and Biological Systems. His group uses analytical and numerical methods to study these systems at the single-particle level, as well as in the limit of large length and time scales where the systems comprise enormous numbers of particles. Additionally, in suitable situations, his group employs methods that bridge these two separate realms.

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Abstract:

In any scenario of heat transfer in a fluid medium, all modes of heat transfer exist, however, the heat transfer by the radiation is neglected in most of the cases, due to many difficulties. Nevertheless, engineers simplify these difficulties to a great extent to perform their tasks. However, in some important/critical applications, these simplifications are not applicable like, combustion, thermal load on the rocket base plate, etc. Apart from these, in some simple applications where the temperature is not very high like, natural cooling of buildings, electronic devices, HAVC systems, etc., the radiation becomes very important. These applications are examples of diffuse radiation, however, some applications like, solar radiation, laser ignition, laser melting and solidification where energy is transferred by the radiation in a preferred direction, belong to collimated beam radiation domain.
The radiation in a participating medium is governed by a spectral radiation transfer equation (s-RTE) which is an integro-differential equation. The analytic solution of s-RTE is very difficult; thus, many techniques to solve the radiative heat transfer have been developed. Another difficulty for a realistic solution of s-RTE is to find the non-gray radiative properties of gases. These properties vary with wavelength along with the temperature, pressure, and species concentration, and can be obtained from the concepts of ''Quantum Mechanics”. However, some databases like CDSD, HITRAN, HI-TEMP, etc. provide the details of line transitions on the spectrum at 296 K and 1 atm pressure. It is impossible to solve s-RTE on these line transitions for any engineering applications as it involves non-isothermal and non-homogeneous medium. However, the full spectrum k-method (FSK method) reorders these random variations of non-gray radiative properties into a smooth function which reduces the computational time for calculation of radiative heat transfer tremendously.
The present talk covers the nature of s-RTE, difficulties in solving this for non-gray radiation, and work progress on collimated beam radiation, the calculation of non-gray properties of gases for a range of thermodynamic states, the FSK method, and the effects of radiation on fluid flow in forced and natural convection problems.

Bio-sketch:

Dr. Pradeep Kumar has earned a Ph.D. from the Indian Institute of Technology Kanpur in 2009 in the area of Thermal Radiation and Fluid Flow Interaction. Afterward, he joined ANSYS Inc. where his primary responsibilities were feature development and maintenance of radiation models in FLUENT. After spending almost six and a half years in ANSYS, he joined the Indian Institute of Technology Mandi in 2015. He is currently working in the area of radiative heat transfer, fluid mechanics, solar devices, etc., and uses computational tools for his research purposes. He is extremely interested in exploring and developing open-source software. His team is currently developing various features of radiative heat transfer like collimated beam radiation, non-gray radiation model, etc. in OpenFOAM - and open-source CFD software for the applications of solar receiver cavity, combustion, thermal load on rocket base plate, etc.

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Abstract:

Wind energy is one of the fastest-growing sources of renewable energy worldwide as well as in India. A key challenge associated with increasing effective utilization of the wind resource is minimizing the effects of wake interactions between the wind turbine wakes. A turbine located in the wake of an upstream turbine is subjected to lower wind speeds and increased turbulence, which leads to lower power production, and is termed as wake loss. In this talk, I will describe large eddy simulation (LES) studies of a novel, multi-rotor wind turbine (MRWT) configuration. In contrast to conventional wind turbines, four three-bladed rotors are mounted on a single tower. The wake of an MRWT is compared to that of a conventional single-rotor wind turbine (SWT) with the same frontal swept area. The wake of the MRWT is found to recover faster than that of the SRWT. The budget analysis shows that this faster wake recovery can be attributed to the perimeter-to-area ratio of the MRWT being twice that of the SRWT. The larger perimeter allows for greater entrainment from the inner portion of the MRWT and leads to the potential for reduced wake losses. Wind farms comprised of MRWTs are investigated and, for the realistic configurations investigated, are found to generate up to 6% more power than equivalent SRWT wind farms. Finally, efforts towards incorporating effects of surface roughness heterogeneities in models of the atmospheric boundary layer and preliminary work on LES of flow over heterogeneously rough boundary layers will be described.

Bio-sketch:

Niranjan S. Ghaisas is an Assistant Professor in the Department of Mechanical and Aerospace Engineering, IIT Hyderabad. He received his B. Tech., M. Sc. (Engg.), and Ph. D. degrees from IIT Kharagpur, IISc Bangalore, and Purdue University, USA, respectively. Before joining IITH, he completed two postdoctoral stints, one at the University of Delaware, and the second at the Center for Turbulence Research, Stanford University. His research interests include high-fidelity simulations for wind energy applications, and multi-material simulations involving compressible fluids and large deformations of solids.

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Abstract:

Human society is going through an unprecedented phase of technology-led development accompanied by the rapid growth of power generation. More than 70% of the power generation is based on the steam cycle, making the power sector the most significant contributor to greenhouse gas emissions. Hence, multipronged efforts are needed towards improving the efficiency of power generation as well as power use. One approach for enhancing these efficiencies involves optimizing the fluid and thermal transport at small length scales through micro and nanoscale surface engineering. This talk provides a brief overview of our work in this area. On the power usage side, the talk focuses upon the increasing power consumption of datacenters – the large computing systems that drive the Information technology-enabled services. One of the approaches to address this issue involves a shift from air cooling to liquid cooling. In addition to reducing the cooling cost, liquid cooling also provides an opportunity to recover the waste heat from data centers for reuse in secondary applications. Moreover, liquid cooling can also be targeted towards efficient cooling of non-uniform microprocessor power maps, thus opening a direction for thermal management of advanced microprocessor architectures such as the 3D-integrated chip-stacks. The talk covers our work on developing liquid-cooled microchannel heat sinks for efficient and passively targeted cooling of microprocessor hotspots. On the side of power generation, we have worked towards developing metallic interfaces that can enhance the thermal transport during condensation – a critical physical process for thermal power generation. Efficient condensation thermal transport requires water to condense as droplets rather than as a continuous liquid condensate film. This dropwise condensation mode requires the condensate droplets to be regularly shedded for periodic nucleation of new droplets. This talk provides an overview of our investigations on small scale condensate droplets' dynamics on micro and nanoscale textures and the corresponding phase change heat transfer. Such investigations have also targeted the development of robust surfaces that can sustain the efficient dropwise condensation under industrially relevant, harsh operating conditions.

Bio-sketch:

Dr. Chander Shekhar Sharma studied BE at Thapar Institute of Engineering and Technology, Patiala, and ME at IISc Bangalore. Subsequently, he worked with General Motors and later joined ETH Zurich for his doctoral studies. His doctoral work focused on microprocessor thermal management and was performed under the supervision of Prof. Dimos Poulikakos and in collaboration with IBM Research, Zurich. After his Ph.D., he worked initially as a Post-doctoral Researcher and later as a Senior Scientist and Lecturer at ETH Zurich. He joined IIT Ropar in 2018 as Assistant Professor and presently leads the Thermofluidics Research Lab in the Dept. of Mechanical Engineering. His research group broadly works in the interdisciplinary area of microfluidics, phase change, and surface wettability with the overall aim of enhancing energetic efficiency in a wide range of applications by using numerical and experimental methods.

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Abstract:

The nonlinear dynamics of a resonantly excited linear oscillator coupled to an array of weakly coupled nonlinear pendulums is investigated under :1:...:1:2 internal resonance between the pendulums and the linear oscillator. In the first part, nonlinear dynamics with periodic oscillations and bifurcations under harmonic excitation of the linear oscillator are investigated, and attention is paid to vibration absorber action. In the second part, the effect of slow sweep of the excitation frequency is considered. In the non-stationary case with linear frequency sweep through the primary resonance region, delays through pitchforks, smooth but rapid transitions through jumps, and transitions from one stable coupled-mode branch to another are studied using numerical simulations of the amplitude equations. Experiments are shown to verify some of the analytical/computational predictions for sufficiently slow sweep rates. Some examples of physical systems exhibiting similar phenomena are also described as motivation.

Bio-sketch:

Anil Bajaj is Alpha P. Jamison Professor of Mechanical Engineering at Purdue University. Last academic year, he was a visiting professor at IITM, Chennai, and the Arcot Ramachandran Chair Professor. He served for 9 years, the William E. and Florence E. Perry Head of Mechanical Engineering and prior to that, he served as the Associate Head for Research and Graduate Education (1998-2010). Dr. Bajaj holds B.Tech. (1973, IITKgp) and M.Tech. (1976, IITK), both in Mechanical Engineering, and Ph.D. in Mechanics (1981, U Minn). His research is in the areas of nonlinear dynamics of structural systems; linear stability and dynamics of systems and structures; brake squeal prediction and sensitivity analysis; dynamics of seat-occupant systems; MEMS designs using nonlinear resonances; and flow-induced dynamics of elastic bodies. He has published more than 220 archival journal and conference papers and has advised (or co-advised) 21 M.S. and 27 Ph.D. students. He received the Purdue University Provost’s Award for Outstanding Graduate Mentor, College of Engineering Faculty Excellence Award for Mentoring, and the College of Engineering Faculty Excellence Award for Team Research. He has taught core undergraduate and graduate courses in Applied Mechanics and Nonlinear Vibrations/Dynamics. He is also very much interested in issues of climate, diversity, and opportunity in education, global collaborations, research and education programs, and student exchanges. Dr. Bajaj is a Fellow- ASME and served for 15 years as Contributing Editor of the Springer journal Nonlinear Dynamics. He was awarded the 2019 Thomas K. Caughey Dynamics Award by the Applied Mechanics Division (AMD) of the ASME.

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Abstract:

With an introduction to the state-of-the-art CFD technology and its various design applications, this seminar will discuss a quick method to draw inlet and outlet velocity diagrams for axial-flow compressors and turbines directly using their key performance parameters, namely, the flow coefficient, the blade loading coefficient, and the degree of reaction or simply reaction. In the conceptual and preliminary aerodynamic designs of these turbomachines, designers will find the method extremely helpful in graphically determining all parameters of blade inlet and outlet velocity triangles for the meanline design (constant blade velocity). Exact equations to compute these parameters will also be presented.

Bio-sketch:

Dr. Bijay Sultanian is internationally known for his contributions in gas turbine aerothermodynamics, heat transfer (airfoil internal and film cooling), secondary air systems modeling, and Computational Fluid Dynamics (CFD). During his 30+ years in the gas turbine industry, Dr. Sultanian has worked in and led technical teams at several organizations, including Allison Gas Turbines (now Rolls-Royce), GE Aircraft Engines (now GE Aviation), GE Power Generation, and Siemens Energy. As an adjunct professor, he taught graduate courses on turbomachinery and intermediate fluid mechanics at the University of Central Florida for ten years. During 1971-81, he made landmark contributions toward the design and development of India’s first liquid rocket engine for the surface-to-air missile Prithvi and the first numerical heat transfer model of steel ingots for optimal operations of soaking pits in India’s steel plants. Dr. Sultanian received BTech in mechanical engineering from the Indian Institute of Technology, Kanpur; MSME from the Indian Institute of Technology, Madras; Ph.D. in mechanical engineering from the Arizona State University, Tempe; and MBA from the Lally School of Management and Technology at Rensselaer Polytechnic Institute, Troy.

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