自由表面を貫通する鉛直円柱まわりの粘性流に関する実験と数値計算

抄録

The characteristics of free-surface turbulence are investigated by experimental and numerical analysis of the viscous flow field around an advancing vertical circular cylinder piercing free-surface. The wave height and flow velocity are measured with a wave height meter of servo type and a hot-film anemometer, respectively. The numerical method used here is the three-dimentional finite volume method to solve the incompressible viscous flow with the free-surface using the free-surface fitted coordinate system. The results reveal the strong interaction of the nonlinear water wave with the separated vortical flow behind the circular cylinder. Some features of the viscous flow field change in the vertical direction by the deformation of free-surface waves. The vertical variation depends on the Froude number as well as the Reynolds number. At deep level the vortex shedding occurs periodically, while at shallow level this periodic phenomenon is not clear under the effect of steep waves with turbulence. The free-surface turbulence starts to appear at the points where the wave gradient vanishes. This result suggests it is attributable to the inherent instability of free-surface.