The Experimental and Numerical Study of Flow Structure and Water Noise Caused by Roughness of the Body

It is well known that eddies shed from rough surface is a main source of water noise. In this paper, the water noise caused by the roughness of the surface of the foil (NACA0020) is numerically and experimentally studied. In the numerical simulation, a mathematical roughness, which comes from the no-slip condition of vortex method, is introduced. The numerical results indicate that the vortex's shedding could be avoided under some mathematical roughness. It corresponds to forward multi-layer in dynamic phenomena. The experiment tried to find how to realize the mathematical roughness in physics. The experiment results showed that certain riblets or slots on the surface could be related to different kinds of mathematical roughness.