Abstract
Fluid frictional resistance is caused on the surface in the flow. This fluid frictional resistance causes the energy loss, which shares the large part of resistance of a transport equipment, such as shipping. The fluid frictional resistance incleases if the surface has the roughness. It was shown that the coherent structures in turbulent boundary layer affect on turbulence transport and enhance turbulence. In this research, we measure the velocity profiles in zero-pressure-gradient boundary layer over the two dimensional rough surface, and we perform the spectral analysis. We will discuss relation between the resistance increase caused by roughness and the coherent structure.
