抄録
Experiments were performed to investigate the effect of a three-dimensional roughness row on boundary-layer transitions on a flat-plate with zero pressure gradient. 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 roughnesses. Further downstream, two adjacent wedges merged together and then a two-dimensional turbulent boundary layer was formed. Mean and fluctuating velocities were measured by hot-wire anemometers and an intermittency factor were obtained. The manner how the three-dimensional turbulence wedges change into two-dimensional boundary layer were investigated. The transition was promoted in the region near the spanwise position at which two wedges interact. The promoted turbulence damped before the promotion spread to the wedge centerline.
