Turbulent boundary layer at plate with suction at various angles

An experimental study of turbulent boundary layers at porous or perforated plates with suction was made, for the purpose of determining the dependence of average and fluctuation velocity profiles on the angle between the direction of suction and the direction of the stream parallel to the plate. The purpose was to supplement already available data pertaining to low suction rates and nongradiental flow with data covering a wide range of suction rates (V sub w/V sub o = 0.002-0.047, V sub w- normal component of velocity at wall, V sub o - velocity of stream beyond boundary layer), negative and positive pressure gradients (with k = (nu/rho) V(3) (DP/DX) ranging from -2.2.10 to the minus 6 power to 4.8.10 to the minus 6 power, nu- kinematic viscosity, rho- density, P- pressure, X- longitudinal coordinate). Measurements were made at a Reynolds N sub R = 2.10 to the 5th power with suction angles alpha = 20 deg, 90 deg, and 160 deg relative to the direction of the stream. The velocity profiles were found to be flattest at alpha = 90 deg and most distorted at alpha = 20 deg (against the stream). Further evaluation of the data has yielded the momentum thickness delta ** of the boundary layer and the ratio of its displacement thickness to momentum thickness delta*/delta** (form factor), also the skin-friction coefficient Cf, as functions of the suction parameter b sub zero = 2F/Cf sub zero (F = V sub w/V sub o, Cf sub zero friction coefficient in absence of suction).