Flows in a Curved Rectangular Channel : 3rd Report, Measurements of Secondary Flow in the Cross Section on the Developing Region of Laminar Flow by Means of LDV

Abstract

One of the 3-D velocity components, which is perpendicular to the main and the radical flows in a 270° curved rectangular channel, was measured in detail by using a Laser-Doppler velocimeter. The developing steady and laminar flow was dealt with under the entry condition of a fully developed laminar flow. The curved rectangular channel having the aspect ratio of 2 and the curvature ratio of 8 was used. The Dean number was 220 and the corresponding Reynolds number was 622. From the LDV measurements at the various angular sections along the main flow direction, the following results were obtained. The secondary flow is directed towards the inner curved wall at the entrance of the curved channel. The counter-rotating vortices in addition to the main secondary flow vortices appeared near the inner wall of the central portion in the 75° angular section. Flow fields obtained by visualization may be quantitatively clarified more accurately by plotting the vectors.