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 joined as a faculty member in the physics department in fall 2020. He holds a PhD degree in Applied Physics from University of Twente the Netherlands (2017). Following his PhD he did a short postdoc at the Max Planck Center for Complex Fluids Dynamics in the Netherlands, and then a 2-year postdoc at Brown university where he worked on the fluid-structure interactions of bioinspired membranes. His research interests are in the mechanics of soft materials and their interactions with fluids. 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. In 2018 he received the European COST prize in Flowing Matter. His very recent research from UMass on airborne transmission risks while driving in passenger cars was featured in the New York times, the Washington Post and several other media.