Theoretical Study on Wave-Induced Pressure and Drift Force on a Vertical Circular Column

Abstract

　With a vertical circular cylinder with infinite draft taken as a simplified model of spar-buoy type offshore wind turbine, a review of theoretical analyses for the linear diffraction problem and the second-order wave drift force is provided. For the linear solution of the velocity potential, it is confirmed that Bessho’s analytical solution method for an integral equation in the source distribution method provides the same result as that by the eigenfunction expansion method. For the wave drift force, the near-field and far-field methods are reviewed, showing that the same explicit-form analytical solution can be obtained. Then, it is also shown that Bessho’s method applying Lagally’s theorem gives the same analytical result for the wave drift force, and furthermore, Tsubogo’s calculation formula given in a reciprocal form on the body surface can be regarded as the same in form as that by the Lagally’s theorem. As a consequence, it is proven that exactly the same analytical result for the wave drift force can be obtained even from Tsubogo’s expression.