Investigation of the flowfield immediately upstream of a hot film probe

The laminar flowfield in a rectangular channel immediately upstream of a hot film gradient probe with two parallel films was investigated in the range of Reynolds number Re _pr= 6 to 95, with the Reynolds number based on the probe diameter and the local flow velocity. For this study a photochromic dye flow visualization technique was used. The results show that the smaller the Reynolds number Re _prthe larger the influence of the probe is upon the flowfield. No distinct influence of the probe location relative to the channel walls on the flow deceleration process immediately upstream of the probe was observed.List of symbols a distance between the hot films - d _h hydraulic diameter - d _pr diameter of the probe body - Reynolds number based on hydraulic diameter and mean flow velocity - Reynolds number based on probe diameter and the undisturbed flow velocity at the centerline of probe - u flow velocity in x-direction - u ₀ undisturbed velocity in the center of the channel - undisturbed mean flow velocity - u(x,y) velocity at position (x,y) - averaged velocity gradient - x coordinate in main flow direction - y coordinate normal to the larger wall of the rectangular channel - z coordinate normal to x and y - v kinematic viscosity