On the effect of polydispersity and rotation on the Brinkman force induced by a cloud of particles on a viscous incompressible flow.

*(English)*Zbl 1420.35240Summary: In this paper, we are interested in the collective friction of a cloud of particles on the viscous incompressible fluid in which they are moving. The particle velocities are assumed to be given and the fluid is assumed to be driven by the stationary Stokes equations. We consider the limit where the number \(N\) of particles goes to infinity with their diameters of order \(1/N\) and their mutual distances of order \(1/ N^{1/3}\). The rigorous convergence of the fluid velocity to a limit which is solution to a stationary Stokes equation set in the full space but with an extra term, referred to as the Brinkman force, was proven in [L. Desvillettes et al., J. Stat. Phys. 131, No. 5, 941–967 (2008; Zbl 1154.76018)] when the particles are identical spheres in prescribed translations. Our result here is an extension to particles of arbitrary shapes in prescribed translations and rotations. The limit Stokes-Brinkman system involves the particle distribution in position, velocity and shape, through the so-called Stokes’ resistance matrices.