Speaker
Description
Modelling the dynamics of particles moving in a liquid is crucial for numerous applications, including marine snow aggregation in oceans and the movement of Lagrangian devices in chemical reactors. While very small particles can be accurately modeled as passive tracers, larger particles require consideration of additional forces. The Maxey-Riley-Gatignol equations (MaRGE) describe the motion of particles that are larger than passive tracers yet not large enough to significantly disturb the surrounding fluid.
However, the Basset history term arising in the MaRGE makes their numerical solution difficult, because the force acting on a particle at a given time depends on its full past trajectory. Therefore, this term is often neglected in practical applications. By analyzing the Finite Time Lyapunov Exponents (FTLE) of a large number of simulated particles in different flows, we show that ignoring the history term leads to substantial qualitative differences not only in individual trajectories but also in the larger scale Lagrangian dynamics.
Based on a recent reformulation of the MaRGE by [S. G. Prasath, V. Vasan, R. Govindarajan, Accurate solution method for the Maxey–Riley equation, and the effects of Basset history, Journal of Fluid Mechanics 868 (2019) 428–460] we present a numerical approach for their solution based on finite differences and compare it against other schemes. We also investigate the use of MaRGE as a dynamic model in a filtering algorithm to track particles via dead reckoning.
