The behavior of a sphere in non-homogeneous flows of a viscoelastic fluid

TLDR: The motion of a sphere, freely suspended in a second-order fluid under the condition of a nonhomogeneous flow field is investigated in this article, neglecting fluid inertia and, to be consistent, also particle inertia.

Abstract: The motion of a sphere, freely suspended in a second-order fluid under the condition of a non-homogeneous flow field is investigated. Neglecting fluid inertia and, to be consistent, also particle inertia a general result is derived. For Couette flow between rotating cylinders as well as for two-dimensional and circular Poiseuille flow, respectively, excellent agreement with experimental observations results. While for the two-dimensional converging flow essentially no deviation from the corresponding results for a Newtonian fluid is found drastic differences show up for the converging flow in a conical duct. Preferably in the narrow cones rather large spheres come to a halt (Uebler-effect). For small spheres no such effect is predicted but a now phenomenon arises: For cones whose half angle lies close to 80° or exceeds that value some of the spheres end up in the region of secondary flow. The resulting separation effect could be diminished by decreasing the cone angle.