EGU23-17324, updated on 05 May 2023
EGU General Assembly 2023
© Author(s) 2023. This work is distributed under
the Creative Commons Attribution 4.0 License.

Inertial torque on a squirmer

Bernhard Mehlig, Fabien Candelier2, Jingran Qiu3, Lihao Zhao3, and Greg Voth4
Bernhard Mehlig et al.
  • 2Aix Marseille Univ, CNRS, IUSTI, Marseille, France
  • 3Department of Engineering Mechanics, Tsinghua University, 100084 Beijing, China
  • 4Department of Physics, Wesleyan University, Middletown, CT 06459, USA

A small spheroid settling in a quiescent fluid experiences an inertial torque that aligns it so that it settles with its broad side first. Here we show that an active particle experiences such a torque too, as it settles in a fluid at rest. For a spherical squirmer, the torque is T = -9/8  mf (vs(0)  x vg(0)), where vs(0)  is the swimming velocity, vg(0) the settling velocity in the Stokes approximation, and mf the equivalent fluid mass. This torque aligns the swimming direction against gravity: swimming up is stable, swimming down is unstable. This talk is based on Candelier, F., Qiu, J., Zhao, L., Voth, G., & Mehlig, B. (2022). Inertial torque on a squirmer. Journal of Fluid Mechanics, 953, R1.

How to cite: Mehlig, B., Candelier, F., Qiu, J., Zhao, L., and Voth, G.: Inertial torque on a squirmer, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-17324,, 2023.