Visualization and Measurement by LDV on Flow Fields in a 180°Curved Duct with Rectangular Cross-Section

Abstract

Flow visualization and LDV measurement were carried out to investigate the secondary flows occurring in an azimuth 180°curved duct and in its attached outlet duct. The Dean number was 220. The flow pattern obtained by the visualization method corresponded to the result conjectured by the LDV measurement at the 180°cross-section, and did not in the outlet duct. The vortex flow pattern observed at the 180°cross-section flows in the downstream as diffusing gradually. The pattern was appeared even at Z0=9Dh. However, the secondary flow was not detected there by the LDV measurement, because the upstream conditions are still preserved in the downstream.