Title: From Wave-Powered Propulsion to Flight with Membrane Wings: Insights Powered by High-Fidelity Immersed Boundary Methods based FSI Simulations
Abstract: The perpetual advancement in computational capabilities, coupled with the continuous evolution of software tools and numerical algorithms, is creating novel avenues for research, exploration, and application at the nexus of computational fluid and structural mechanics. Fish leverage their remarkably flexible bodies and fins to harness energy from vortices, propelling themselves with an elegance and efficiency that captivates engineers. Bats fly with unparalleled agility and speed by using their flexible membrane wings. Wave-assisted propulsion (WAP) systems, utilizing elastically mounted hydrofoils, convert wave energy into thrust. Each of these problems involve a complex and elegant interplay between fluid dynamics and structural mechanics. Historically, investigations into such phenomena were constrained by available tools, but modern computational advancements now facilitate exploration of these multi-physics challenges with an unprecedented level of fidelity, precision, and realism. In my presentation, I will discuss projects that harness the capabilities of high-fidelity sharp-interface immersed boundary methods to address a spectrum of challenging problems in engineering and biology involving fluid-structure interaction.
Bio: Rajat Mittal is a fluid dynamicist and a professor of mechanical engineering at Johns Hopkins University (JHU) with a secondary appointment in the School of Medicine. Mittal earned his bachelor’s degree in Aeronautical Engineering from the Indian Institute of Technology, Kanpur, in 1989. He then pursued a MS in Aerospace Engineering from the University of Florida, graduating in 1991, followed by a Ph.D. in Applied Mechanics from the University of Illinois at Urbana-Champaign in 1995. Mittal’s academic journey includes postdoctoral research at the Center for Turbulence Research at Stanford University from 1995-1996, where he focused on large-eddy simulation. He began his teaching career at the University of Florida’s in 1996 and from 2001 to 2009, he was a faculty member at George Washington University. Since 2009, he has been a professor at Johns Hopkins University. Mittal is recognized for his seminal contributions in immersed boundary methods and their applications in fluid flow problems. His research group focuses on computational fluid dynamics, vortex dominated flows, biofluid mechanics, bioinspired engineering, and flow control. His research has made significant impact in fluid-structure interaction, cardiology, bio-locomotion, bioacoustics, COVID biophysics, gastric digestion, active flow control, and turbulent flows. He is the recipient of the 1996 Francois Frenkiel and the 2022 Stanley Corrsin Awards from the Division of Fluid Dynamics of the American Physical Society (APS), and the 2006 Lewis Moody as well as 2021 Freeman Scholar Awards from the American Society of Mechanical Engineers (ASME). He is a Fellow of ASME and the APS, and an Associate Fellow of the American Institute of Aeronautics and Astronautics. He is an associate editor of several journals including the Journal of Computational Physics and Physics of Fluids.
Title: Supercritical Fluids: An Enigma
Abstract: Cagniard de la Tour discovered the disappearance of the interface between the liquid and vapor at a certain pressure and temperature, in 1822. This was later confirmed by Faraday (1845) and named by Andrews as the “critical point” in 1869. van der Waals, in 1873, parameterized the Andrew’s data using a cubic equation of state, and claimed the existence of singularity in the fluid density at CP. This was the beginning of the knowledge of anomaly at the critical point. In 1882, Hannay pointed out that the “continuity hypothesis” was inconsistent with the experimental results of Andrews. Michels dispelled the doubts on actual existence of the critical point in 1937. Widom, in 1963, showed that some of the fluid properties, including specific heat, exhibit maxima at the critical point. Consequently, the critical point was shown as the end point of the liquid-vapor curve on the phase diagram.
In the beginning of this century, Nishikawa observed that inhomogeneity is the most fundamental concept of the SC fluids, which gives rise to a ridge on the phase diagram. This ridge separates the SC region in two parts: SC “liquid-like” (SCLL) and SC “gas-like” (SCGL) states. The existence of these two states has been verified by many researchers, both experimentally and theoretically; obviously, the SC fluids do not have a homogenous single phase. Subsequently, Widom line based on the maxima of the specific heat was proposed to divide the SCLL and SCGL states. It was widely accepted that there exists an anomalous region in the vicinity of critical point that is characterized by large-scale variations in fluid properties, including the inversions. The anomalous region is prone to flow oscillations, thermal instabilities, and deteriorated heat transfer. Interestingly, the research on anomalies in fluid properties were focused on the states beyond the critical point, but not on the subcritical side.
Our team has demonstrated that the subcritical liquid should also be divided into two parts: (a) one the “regular liquid” and (b) the other where the liquid properties are anomalous and may exhibit similar behavior as the SCLL. Apparently, the second state of the subcritical liquid and the first state of the SC fluid (liquid-like) ought to be continuous. Consequently, a hypothetical modification to the phase diagram was proposed. Recently, the anomalous region has been successfully delimited by employing a Gibbs free energy (g)-based thermodynamic model that takes a unified approach from the subcritical to supercritical state. This model gives an expanded thermodynamic definition of the critical point. It is a state, where the third derivative of Gibbs free energy is zero, i.e., g = 0, the anomaly in fluid’s behavior is maximal, and the governing parameters, cp* (= cp/T), b* (= vb), and k* (= vk) approach infinity. Beyond the anomalous states, the thermophysical properties of SC fluids behave monotonically.
However, the behavior of fluids at high SC pressures and temperatures is still unknown, and hence, the mystery surrounding the supercritical fluids persists. It is expected that many new characteristics of the fluids would be revealed if we can analyze the properties far away from the critical point. Indeed, this knowledge would have a profound impact on our understanding of many terrestrial and extra-terrestrial natural phenomena.
With regard to scientific and technological applications of supercritical fluids, they are being extensively used in chemical, pharmaceutical, food, and materials processing industries, owing to their high solubility at SC conditions. Significant research are also underway in the areas of supercritical heat exchangers, nuclear/fossil fuel thermal power plants, and CO2 energy conversion systems. However, SC fluids have far more potential for their applications in ultra-high-capacity, energy-efficient, and environmentally less-unfriendly thermal systems and pipeline transport of fluids. Many of the above physical, thermodynamic, transport, and application aspects of SC fluids will be elaborated during the presentation.
Bio: Dr. Vish Prasad is the Professor of Mechanical Engineering at University of North Texas. His research includes the broad areas of supercritical fluids, convective heat transfer, heat transfer in porous media, energy systems, advanced materials processing and manufacturing, and computational methods. Dr. Prasad has published over two hundred twenty-five invited and/or refereed articles and made over two hundred conference/seminar presentations. He has served on many Editorial Advisory Boards, as an Editor or Co-editor of several archival journals and monographs, and a Co-Editor of the Springer Handbook of Crystal Growth. Currently, he is the Editor-in-Chief of the SpringerNature Mechanical Engineering Series and the Annual Review of Heat Transfer. Dr. Prasad is a member of the Board of Directors of ASTFE and a Fellow of ASME and ASTFE.
Dr. Prasad has received 2020 Heat Transfer Memorial Award from ASME, 2011 Michael P. Malone International Leadership Award from the Association of Public and Land-Grant Universities (APLU), 2010 Award for building Texas-India Educational Partnership from the Greater Dallas Indo-American Chambers of Commerce, 2007 Educator of the Year Award from Great Minds in STEM, a national Hispanic organization, and 2006 Academic Excellence Medal from the Latin American and Caribbean Consortium of Engineering Institutions.
Dr. Prasad’s previous academic positions include Assistant and Associate Professor at Columbia University, Leading Professor/Professor at Stony Brook University, Distinguished Professor at Florida International University, and Visiting Distinguished Professor at Indian Institute of Technology, Kanpur. In addition, he has served in many academic leadership roles, including the President of Mody University of Science and Technology (India), Vice President for Research and Economic Development of University of North Texas, Executive Dean/Dean of Engineering and Computing of Florida International University, Interim Dean of Engineering at Wichita State University, and Associate Dean of Engineering (Research and Graduate Studies) at Stony Brook University.
Title: Co-Optimization of Ion and Heat Transport for Efficient Energy Conversion
Abstract: Efficient energy conversion such as chemical-to-electrical energy or heat pumping is critical to tackle climate change. In this talk I will discuss how co-optimization of ions and heat transport can lead to significant advancement in energy conversion technologies such as high temperature solid oxide fuel cell/electrolyzer or air conditioning/heat pumping. Examples will include recent advancement in high temperature solid oxide electrolyzer for hydrogen production, carbon capture from high temperature fuel cells and recently invented Isocaloric refrigeration cycle.
Bio: Ravi Prasher is the Chief Technology Officer of Bloom Energy. He also serves as an adjunct professor in the Department of Mechanical Engineering at UC Berkeley. Prior to joining Bloom Energy, Ravi was the Associate Lab Director of Energy Technology Area at Lawrence Berkeley National Laboratory (LBNL). His responsibilities included managing research and development in a wide variety of areas, including fuel cells, hydrogen production, storage and transport, electrochemical and thermal storage, carbon capture, microgrids, and renewable energy among others. He was also a Senior Scientist at LBNL where he conducted research in thermal science and engineering. Ravi’s experience includes being one of the first program directors at US DOE’s high-risk high-reward funding agency, ARPA-E, and serving as the technology development manager of Intel’s thermal management group. Ravi has published 150+ archival papers in top science and engineering journals and holds more than 35 patents. He is a member of the US National Academy of Engineering and a fellow of ASME. Ravi obtained his B.Tech. from IIT Delhi and PhD from Arizona State University.