抄録
This is a fundamental stydy on three-dimensional effects on hydrodynamic forces acting on a semi-circular cylinder in free-surface. The pressure distribution on cylinder surface and the distribution of hydrodynamic forces in the direction of the cylinder axis are solved by using the Integral Equations and are compared with those of two dimensions. "3D effects" of a floating cylinder seem to be composed of "end-effects" and "free-surface effects". Free-surface effects are very severe to the whole flow field around the cylinder, especially in radiation problems. Hydrodynamic forces acting on the cylinder sections vary with the wave number, which could be explained by the waves generated along the cylinder, because changes in forces are strongly concerned with ratios of the wave length to the cylinder length. In diffractin problems, 3D effects is not so severe that we could assume half part of center of the cylinder as two dimensions in allowance of 10% error.
