Reynolds Number Dependences of Velocity Field and Fluid Mixing in Partitioned-Pipe Mixer

Abstract

The dependence of the chaotic mixing of fluids on the Reynolds number Re in a partitioned-pipe mixer (PPM), composed of alternately placed horizontal and vertical plates in a rotating cylinder, is studied. By numerically calculating the steady velocity field due to this rotation and an axial pressure gradient, we find that the three-dimensionality of the velocity field becomes weaker with increasing Re from zero. From the computation of trajectories of fluid particles in this velocity field, we also find that tubular transport barriers extending straight in the axial direction initially expand as Re is increased. Although these barriers usually disappear with the further increase in Re , some of them survive even up to a relatively large Re when the ratio of the lengths of neighboring plates is markedly different from unity. Moreover, high-shear regions are observed away from the rigid walls for a sufficiently large Re . Therefore, we conclude that the size of the transport barriers does not simply depend...