Wall Shear Stress around Right-Angle Branch and Time Variation of Separation Flow in Side Branch.

Abstract

In the present study, the wall shear stress and the flow structure in the right angle branch have been studied experimentally in laminar steady flow using a laser Doppler velocimeter. The side branch, 14mm in diameter, bifurcates at a right angle from the trunk, 24mm in diameter, and both upstream and downstream corners at the entrance of the side branch are square edged. In the upstream trunk, the wall shear stress at the upstream corner acquires a very large magnitude owing to the deflection of the core flow. Consequently, the change of wall shear stress around the upstream corner is comparable to that around the flow divider. There is a periodical change of velocity along the separation surface in the side branch. There is a high probability that this phenomenon is similar to that of the Karman vortex street.