Equilibrium tilt of slippery elliptical rods in creeping simple shear

It is shown that shape anisotropy and intrinsic surface slip lead to equilibrium tilt of slippery particles in a creeping simple shear flow, even for nearly shape-isotropic particles with a cross-section that is close to circular provided the Navier-slip length is sufficiently large. We study a rigid particle with an elliptical cross-section, and of infinite extent in the vorticity direction, in simple shear. A Navier-slip boundary condition is imposed on its surface. When a Navier-slip length parameter λ is infinite, an analytical solution is derived for the Stokes flow around a particle tilting in equilibrium at an angle (1/2)cos−1((1−k)/(1+k)) to the flow direction where 0≤k≤1 is the ratio of the semi-minor to semi-major axes of its elliptical cross-section. A regular perturbation analysis about this analytical solution is then performed for small values of 1/λ and a numerical continuation method implemented for larger values. It is found that an equilibrium continues to exist for any anisotropic particle k