1025 LAMINAR-TURBULENT TRANSITION OF THE FLAT-PLATE BOUNDARY LAYER BY A LINE OF ROUGHNESS ELEMENTS (Variation of Turbulence Energy Due to Interference of Turbulence Wedges)

抄録

Experiments were performed to investigate the effect of a line of roughness elements on a flat-plate boundary layer transition. Each of 11 roughness elements was a cylinder 2 mm in both diameter d and height k, forming a row with an interval of a 22 mm in the line of elements in the spanwise direction. Wedge-shaped turbulent regions ("turbulence wedges") developed downstream from the respective roughness elements. Farther downstream, two adjacent wedges merged and a two-dimensional turbulent boundary layer was then formed. Mean and fluctuating velocities, Reynolds shear stress and turbulent energy production rates were measured by hot wire anemometers inside and outside the wedge regions. The relationship between the fluctuating velocity and the turbulent energy production rates was examined.