Study on steady flow approximation in turning simulation of ship in waves

Abstract

This study considers the effects of steady flow approximation in the analysis of ship maneuvering in waves. To this end, the ship motion due to waves is analyzed using the three-dimensional time-domain Rankine panel method, and the wave drift forces acting on a ship are calculated by applying the near-field method to directly integrate the pressure on the hull surface. In this seakeeping analysis, the steady flow induced by the operation velocity of the ship is approximated by a uniform flow or double-body flow. The ship maneuvering in waves not only advances forward but also drifts and rotates; hence, it can be regarded as a lifting body. Therefore, the vortex flow generated at the sharp end of the hull is also modeled and reflected in the steady-flow approximation. In order to investigate how the seakeeping performance is determined according to the approximation method, ship motions and drift forces induced by waves are computed for the ship moving forward or obliquely. Lastly, the numerical simulation for the turning test in a regular wave is performed based on the time-domain direct coupling method. Based on the accuracies of computation results compared with existing experimental data, the steady-flow induced coupling effects between seakeeping and maneuvering quantities are discussed.