직접수치모사를 이용한 공간발달하는 난류경계층에서의 표면조도의 영향

Abstract

The effects of surface roughness on a spatially developing turbulent boundary layer were investigated by comparing direct numerical simulations over rough and smooth walls. The Reynolds number based on the momentum thickness is Re<SUB>θ</SUB>≈300~1400. The roughness is composed of periodically arranged two-dimensional spanwise rods and roughness height is k=1.5θ<SUB>in</SUB>, which corresponds to k/δ≈0.045~0.125. Using very large domain along the streamwise direction, spatially developing characteristics of roughness effects in the outer layer are observed. Along the downstream, the wall friction velocity approaches to a constant value and the similarity profiles of turbulent stresses could be obtained. The roughness effects of turbulent stresses in the outer layer were more pronounced along the downstream. This investigation shows that the roughness effects on turbulent stresses are not restricted to the roughness sublayer but are felt throughout the boundary layer.