LAMINAR-TURBULENT TRAN ITION BY A INGLE ROUGHNE ELEMENT ON A FLAT PLATE

摘要

A turbulence wedge which develops downstream from a single roughness element placed in a laminar boundary layer on a flat plate is experimentally investigated Mean and fluctuating velocities and the intermittency factor were measured Contours of the wedge and its development in the normal and spanwise directions were clarified by drawing intermittency contour lines The mean properties inside of the wedge just behind the roughness did not reach fully developed turbulence, and gradually developed in the downstream direction The contour of the wedge is not formed by straight lines very close to or far from the roughness, and the extent of the wedge in which the lines are straight is limited Since just behind the roughness, distributions of the mean and fluctuating velocities are complicatedly distorted, the existence of several vortices is presumed The intermittency contour lines in the section normal to the flow are also presented.