Studies on Insertion Effects of Hot-Wire Probe upon the Velocity Measurement of Boundary Layer with Separation and Reattachment

Abstract

In this research, insertion effects of hot-wire probe (HWP) upon the velocity measurement of boundary layer with separation and reattachment are investigated. Constant-temperature anemometry (CTA) and PIV measurements are performed on the suction side of an airfoil in the low-pressure turbine cascade. In the past research, we found flow may change due to insertion of the HWP in separation and reattachment region. Therefore, the aim of this paper is to find the insertion angle (θ_HWP) which is the angle between wall-normal direction and HWP to enable to reduce the insertion effects by means of particle image velocimetry (PIV). Especially, we focused on the survey in separation area because the separated shear layer is significantly affected by the external disturbance. The tip of the HWP was fixed at y/p=0.0125 in separation area, and changes in the flow field when the θ_HWP was changed were investigated. Time-averaged velocity distributions obtained in the case of HWP inserted compared with those in the case of HWP ejected. As a result, θ_HWP= 65°was the best insertion angle to reduce the effects in this research. Furthermore, CTA measurement was conducted with the insertion angle. Finally, the velocity distributions of both PIV and CTA were good agreement.