Experiments on the Boundary Layer of an Oscillating Circular Cylinder

Abstract

The mean and fluctuating velocities in the boundary layer of a circular cylinder, oscillating in the direction of the wind tunnel stream, have been measured using the hot-wire anemometer. The results have been compared with theoretical predictions. (1) The effect of the velocity fluctuation on the mean velocity in the boundary layer is found to be negligible when the ratio of the amplitude of fluctuation of the outer flow to the mean velocity is less than 0.3. This agrees with theoretical predictions. (2) Upstream of the point of minimum pressure, the effect of the frequency of oscillation on the boundary layer is found to be negligible when the frequency parameter is less than 0.3. The results of calculation, on the assumption of quasisteady flows, agree well with experimental velocity distributions. (3) When the separation point is approached, the discrepancy between the theoretical and experimental results increases. Although the discrepancy is mainly attributable to the premature truncation of the series solution used in the theoretical calculation, other causes are left to be explored.