7. Hydrodynamic Forces on a Ship Moving at Forward Speed in Waves

概要

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We present a new numerical scheme of evaluating the Green function for a ship moving at forward speed in waves. A single integral expression, whose original form was given by Bessho, is integrated along a path on which integrand does not oscillate. Once this 'steepest descent path' is found numerically, integration itself is straightforward and efficient in computing time. This scheme is complemented by a semi-analytical method effective for some values of parameters when the numerical integration loses its efficiency. Using this scheme radiation and diffraction problems at forward speed are solved for a prolate spheroid submerged under the free surface: the body surface is divided into a number of panels on which velocity potential is assumed constant; the integral equation for the velocity potential is solved on this approximation. Convergence and degree of numerical accuracy of the solutions such as added mass and damping forces are investigated by increasing the number of discretized panels on the body surface to do validation of the numerical procedure. Diffraction wave pattern obtained from the solution of diffraction problem is in good agreement with the measured in model tests. This implies that the present scheme is correct in predicting the wave field away from the body; it predicts well added resistance strongly associated with the far field wave elevations.
社団法人日本船舶海洋工学会の論文