Research on wind resistance characteristics of transverse rod-roughened surface

The wind field above transverse rod-roughened surface is investigated using the Reynolds stress model (RSM). The RSM abandons Boussinesq hypothesis that the Reynolds stress has linear relationship with mean velocity gradient. The RSM is more realistic because the convection and diffusion effects of Reynolds stress are considered. The pitch width ratio w/b、aspect ratio h/b and pitch height ratio w/h are regarded as the main characteristics parameters of transverse rod-roughened surface to study the effect of roughness elements distribution density and cross section size on rough surface resistance. Numerical results indicate that the mean frictional resistance first decreases then rises with the increasing of w/b, while the variation of mean form resistance and mean skin resistance show contrary trends and the variation of h/b has nothing to do with these trends. The w/b corresponding to the maximum mean skin resistance increases with h/b, and the w/h corresponding to that keeps around 7. It suggests that the pitch height ratio is the key parameter of transverse rod-roughened surface and the maximum skin resistance occurs at w/h=7.