Abstract
In the present study, the distributions of time-averaged and fluctuated wall shear stresses downstream from an orifice were measured using a Flow Vector Sensor of MEMS. The air flow was supplied to a circular pipe from a blow-down wind tunnel. The diameter of the pipe is D = 51 mm. The diameter ratio are β(=d/D;d,diameter of orifice) = 0.41, 0.5 and 0.62. Near the wall in the recirculating region, the minimum mean skin friction coefficient was located at approximately x/h = 5, and the maximum RMS intensity skin friction coefficient was located at approximately x/h = 7.5. The minimum mean skin friction coefficient decreased with increasing in Reynolds number. The maximum RMS intensity skin friction coefficient increased with increasing in the Reynolds number. The similarity of mean and RMS intensity skin friction coefficients with Reynolds number based a height of orifice and a bulk velocity at orifice was found.
