Mixing-effective motion of high viscosity fluid around a rotating ellipticcylinder

Mixing-effective motions are both numerically and experimentally studied fo r a very viscous fluid around a rotating elliptic cylinder installed in a c ylindrical vessel. A two-dimensional direct numerical simulation was conduc ted in an elliptic boundary-fitted curvilinear coordinate system rotating a t the same angular velocity as the elliptic cylinder. Time-dependent stream lines and streaklines were observed with the aid of visualization technique . It is found that a mixing-effective (folding) motion actually occurs in t he vicinity of the edges of the elliptic cylinder, and that such a motion m ay result from the unstableness of hyperbolic fixed points on an integrable two-dimensional heteroclinic orbit due to experimentally unavoidable three -dimensional disturbances.