Experimental study on wind characteristics around a two-dimension escapement in a uniform flow

This paper describes the experimental study of a non-stratified airflow past a two-dimensional escarpment in a uniform flow. The Reynolds number, based on the uniform flow and the height of the escarpment, is about 10⁴. The slope gradient of the escarpment is 25, 35 and 45 degree. Airflows around the escarpment include the unsteady separated and reattaching flow (hereafter called a "separation bubble"), where the separation occurs from a sharp comer. Attention is focused on an influence of a surface roughness on airflow characteristics in a wake region. For this purpose, the velocity components were measured with the X-wire probe and the split-film probe. In addition, the flow visualization was performed by using the smoke-wire technique. Through comparison between the experimental results with the surface roughness and those without it, the significant difference in the airflow characteristics is confirmed in the separation bubble. This is mainly due to the size in the separation bubble. The size in the separation bubble with the surface roughness is much larger than the one without it. In the case under an imposition of the surface roughness, the velocity is strongly defected near the slope surface. As a result, the production of the vorticity in the separated shear layer is also inhibited, leading to the elongation in the separation bubble.