Experimental and numerical study of chaotic mixing in a curved-square duct flow

Chaotic mixing in a curved-square duct flow is studied experimentally and numerically. Two walls of the channel (inner and top walls) rotate around the center of curvature and a pressure gradient is imposed in the direction of the exit of the channel. There are two parameters dominating the flow, the Dean number De (α the pressure gradient and the Reynolds number) and the Taylor number Tr (α the angular velocity of the wall rotation). It is found that good mixing occurs for very low Dean numbers (low Reynolds numbers) if De ≤ 0.1 |Tr| because Lagrangian chaos occurs for that case. The flow is studied both experimentally and numerically which agree with each other very well. The mechanism of chaotic mixing is investigated by observing the entanglement process of streamlines.