The effect of steady flow potential on the ship motions in waves

A three-dimensional method for predicting the motions of a ship running in waves is presented. Basically the method developed here is based on the source distribution technique and the general formulations include the effect of steady flow and unsteady flow. Three algorithms are used for treating the corresponding Green functions and derivatives, i.e. (1) The ness & Smith algorithm for the part of simple source Yr. (2) The complex plane contour integral of Shen & Farell algorithm for the Double integral of steady flow. (3) The series expansions of Telste & Noblesse algorithm for the Cauchy principal value integral of unsteady flow. The steady flow potential is especially considered in the calculations of diffraction and radiation problems, and the effects on ship motions are discussed. The results indicate that the effect of steady flow is generally small, but it still cannot be neglected in some cases especially for Long Raves. It is also interesting to find that the steady flow effect depends on the fore-aft configuration of the ship.