Abstract
Experiments were performed to investigate the effect of a line of roughness elements on flat-plate boundary layer transition. Each roughness element was a cylinder 2 mm in both diameter and height. Eleven elements formed a row in the spanwise direction. Wedge-shaped turbulent regions, "turbulence wedges," developed downstream from the respective roughness elements. Further downstream, two adjacent wedges merged together and then a two-dimensional turbulent boundary layer was formed. Mean and fluctuating velocities of streamwise and spanwise direction were measured by hot-wire anemometers. The Reynolds share stress, turbulent energy production rates and turbulent energy dissipation rates, etc. were obtained. Downstream variations between on the center line and the mid-point of the roughness elements were compared.
