Varghese Mathai
University of Massachusetts-Amherst
Seminar Information
The interaction of deformable materials with fluid flows can produce a variety of emergent phenomena, many of them advantageous in engineering. In this talk I will present two multiphase flow systems where interfacial mechanics contribute to enhancements in thermal and mechanical energy extraction. In the first part, I will discuss flow modifications that result from the introduction of millimetric gas/vapor bubbles in thermally driven turbulent flow. Specifically, we will show how adding a small volume fraction (~ 1%) of a low-boiling liquid to a water-based thermal convection system can generate a self-sustained cycle of rising vapor bubbles and settling droplets, with a severalfold increase in heat transfer efficiency. The roles of phase change and bubble kinematics in the transport processes will be discussed. In the second part of my talk, I will discuss the fluid-structure interactions of an oscillating membrane hydrofoil in a uniform flow. We reveal the mechanisms by which the membrane’s deformability contributes to a higher power extraction as compared a rigid hydrofoil. Potential benefits of using soft materials for energy extraction in tidal and fluvial environments will also be outlined.
Varghese Mathai is a faculty member in the department of physics at the University of Massachusetts, Amherst. He completed his PhD in Applied Physics from the University of Twente, the Netherlands in 2017, and then did a postdoc at Brown university, where he worked on the fluid-structure interactions of bioinspired materials. His current group’s research interests are primarily in bubbly and particle-laden flows, and in the fluid-structure interaction of soft materials. Varghese’s PhD research was selected for the ERCOFTAC Da Vinci award for top 5 PhD theses in Europe in the area of Fluid mechanics, Turbulence and Combustion, and in 2018, he received the European COST prize for Best Researcher in Flowing Matter. His recent research on COVID-19 and airborne transmission risks in passenger cars was featured in the New York times, and several other media, and appears among the current CDC guidelines for transmission mitigation efforts.