Motion of a hot particle in viscous fluids

Simons Foundation

I will talk about the motion of a hot particle in a viscous liquid at low Reynolds numbers, which is inspired by recent experiments with Brownian particles heated by a laser. The difference in temperature between a particle and the ambient fluid causes a spatial variation of the viscosity in the vicinity of the solid body. For low Péclet numbers it is possible to derive a general analytical expression determining the force and the torque on a particle by exploiting the Lorentz reciprocal theorem. Among other results, we find for dipolar thermal fields that there is coupling of the translational and rotational motions when there are local viscosity variations; such coupling is absent in an isothermal fluid.