Lift force on spherical drops in inhomogeneous flows

• Applicant: Dr. Pengyu Shi
• Subject Area: Fluid Mechanics
• Term: since 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 501298479

Predicting the motion of drops in dispersed two-phase flows is a key problem in fluid mechanics that has a bearing on a wide range of applications from epidemiology, microfluidic biotechnologies to chemical or petroleum engineering. Drops maintain a spherical shape if either interfacial tension forces or viscous dissipation dominate significantly inertial and buoyancy effects. These conditions are obeyed in practice by small size fluid particles. Under steady state, the motion of a spherical drop is governed by three distinct hydrodynamic forces: the drag (balanced by buoyancy effects), which tends to slow down the relative motion, the lift force, which is perpendicular to the relative motion and causes cross-stream migration of drops, and added mass force. Currently, while much experimental and numerical studies have been devoted to the drag and theoretical/numerical investigations have clarified added mass effects, only little is known about the lift, despite its nearly equal importance in predicting the drop motion in complex flows. The present proposal is intended for a post-doc period at IMFT (France) in the research group of Prof. D. Legendre who uses computational and theoretical approaches to investigate the dynamics of bubbles, drops, and particles in inhomogeneous and turbulent flows. The main focus of the proposal is to explore in detail the lift force acting on spherical drops moving in inhomogeneous flows. More specifically, this includes: (i) lift in unbounded linear shear flow, (ii) lift in unbounded quadratic shear flow, (iii) assessment of wall effects, and (iv) pairwise interaction. To make progress on these various aspects, theoretical analysis mostly by means of matched asymptotic expansions will be used to derive analytical solutions at low Reynolds numbers, where these are still missing in particular for the topic (ii). At moderate-to-high Reynolds numbers, direct numerical simulations (DNS) will be performed using the JADIM code developed at the IMFT. This post-doc will provide the applicant the opportunity to learn new skills, produce original scientific information and to build up a scientific network in France.

• DFG Programme: WBP Fellowship
• International Connection: France
• Host: Professor Dominique Legendre