Abstract
Interactions of suspended particles with interfaces are important in many natural and engineered systems including blood flow, lubricated bearings, and microfluidics. In this talk we discuss how interface deformation is produced by, and subsequently modifies, particle motion through hydrodynamic interactions. Focusing on non-inertial flows, we elucidate with the help of examples how these interactions can be understood as induced nonlinear hydroelastic forces and torques on the particles. We first discuss the combined translation and rotation of a cylinder on a soft substrate and find that the cylinder may either “roll” or “slide” depending on the stiffness of the substrate. We show that this behavior occurs from an interplay of hydroelastic forces, torques and end-effects, leading to a rolling-to-sliding transition at a characteristic stiffness scale that depends on the aspect ratio of the cylinder. Next, we present experiments showing that a particle sedimenting near a suspended flexible elastic membrane experiences a repulsive drift away from the sheet. This lift is induced by the deformation of the sheet and is quantitatively confirmed by a theory that accounts for its tension and the bending. Finally, we show how the analyses in these specific examples are encompassed by a unified theoretical framework that makes transparent the relation between nonlinear hydroelastic lift forces and the underlying linear response of the soft interface. Motivated by recent atomic force microscopy of lift forces, we argue that this general framework can be applied as a tool for non-contact oscillatory micro-rheometry of complex soft materials.
About the Speaker
Bhargav Rallabandi holds a B.S. degree in Mechanical Engineering from the National Institute of Technology Karnataka, and M.S. and Ph.D. degrees in Theoretical and Applied Mechanics from the University of Illinois at Urbana-Champaign. He was a postdoctoral researcher at Princeton University prior to joining the Mechanical Engineering faculty at the University of California, Riverside in 2018. His research focuses on transport of particulate suspensions, including microscale acoustics, fluid-elastic interactions and colloidal self-propulsion.
Host: Professor Sascha Hilgenfeldt & Mattia Gazzola
