0n the Description of Non-Harmonic Problems in the Frequency Domain (2nd Report) : Memory Effect Function of a Three-Dimensional Body

Abstract

Concerning the study of non-harmonic wave problems, the hydrodynamic responses, memory effect functions, generated by an impulse in oscillating velocity of a body are required. In the previous paper, the authors discussed a calculation method for memory effect functions of a two-dimensional body. A rational calculation method for the asymptotic values of the damping coefficient in the high frequency range was shown and the memory effect functions were evaluated from the calculation in the frequency domain. In this paper, the same problem of a three-dimensional body is discussed. Firstly, the memory effect functions for a ship-like body are evaluated by use of the strip method. Secondly, the asymptotic value of the damping coefficients in the high frequency range for forced heaving and swaying hemisphere are presented by extending the Hermans method and memory effect functions are obtained by the same procedure mentioned in the previous paper. Comparisons between the results obtained from the Fourier transform of the memory effect functions and the hydrodynamic coefficients predicted by Havelock and Kim show satisfactory agreement. The method presented herein can be extended to solve the problem for an arbitrary body.