Heat and Fluid Flow in Expanding Concentric Annular Flow-Passage With Rotating Inner-Wall

An annular flow passage with a rotating inner wall is widely seen in many industrial apparatuses. In this type of passages, the flow is disturbed by the multiple reasons: the centrifugal forces due to the streamline curvature in the through-flow and circumferential directions, the centrifugally driven flow in the through-flow direction depending on the passage inclination, and the adverse pressure gradient due to the flow-passage expansion resulting in the flow separation. In this study, heat and fluid flow in this type of annular flow passage was numerically investigated. The large eddy simulation with a Lagrangian dynamic subgrid-scale model was performed with a finite difference method. Two different flow passages (concave and convex types) were examined. Inlet through-flow Reynolds number was Re_in = 1000 and the Taylor number was varied among Ta = 0, 1000, 2000, and 4000. When the rotation speed was gradually increased, the flow changed into spiral structure at first and then fragmented vortex structure in the downstream region. The flow structure changed depending on the passage type, the Taylor number, and the position in the through-flow and wall-normal directions. The Nusselt number showed a complicated profile, and near the outlet the Nusselt number on the outer wall became very high because of the low-temperature inflow compensating the centrifugally driven outflow near the rotating inner wall.