Due to high speed and excellent hydrodynamics of the planing hull, crafts are applied in unmanned surface vehicle, racing and military aspects. In present study, the hydrodynamic performance of a planing hull in calm water was investigated using RANS method including overset mesh and rigid body motion method and compared with the Savitsky's method and experimental results. The aim of this study was to assess the effects of overset mesh method and rigid body motion method on numerical simulation of the planing hull. The total resistance, sinkage and trim angle computed by three methods were evaluated at different Froude numbers and compared with the experimental results. And the pressure distributions and wave patterns around the planing hull were also compared. Based on the experimental results, the comparison between the RANS method and Savitsky's method showed that the numerical approach is more accurate than the semi-empirical method. It should be noted that the Savitsky's method computes the resistance in a short time while the RANS method requires more time. The overset mesh method is more sensitive to the porpoising phenomenon than the rigid body motion method in simulation of the planing hull.

INTRODUCTION

High-speed planing crafts have been widely applied ranging from small pleasure boats to large maritime transportation due to its high speed and excellent hydrodynamic performance. In the planing mode, the hydrodynamic lift force overcomes most of the hull's weight in the vertical direction. With the increase of the velocity of planing craft, the dynamic trim angle and wetted length will be changed, which is quite different from the displacement vessel. It's very important to make an accuracy prediction and understanding of the behavior of the planing hull under various operating conditions.

Numerous investigations have been done on hydrodynamic analysis of high-speed planing hulls over the past several decades. A large experimental study of the pressure distributions on flat plates and deadrise planing surfaces was conducted by Kapryan and Boyd (1955). They found that Smiley's method (1951b) was adequate for flat plates and existing methods for deadrise surfaces were poor agreement with experimental data. Clement and Blount (1963) presented an extensive model tests on the resistance of the Series 62. Savitsky (1964) conducted a series of tests on prismatic planing hull to estimate the hydrodynamics acting on planing craft and obtained semi-empirical equations through the regression procedure, which made great contribution to understanding and modeling of planing crafts. The planing hull is assumed to be in the planing mode in his formulas and the trim angle and the total resistance of the planing hull can be determined by this method. And Savitsky et al. (2007) considered the effects of the whisker spray on the resistance in calm water. Fridsma (1969) carried out the systematic model experiments in calm water and regular waves included results of a series of constant dedarise angle planing hull with different lengths, loads and longitudinal center of gravity. He studied the effects of some design parameters, such as the trim angle, deadrise and length-beam ratio on the resistance performance, heave and pitch motions and impact accelerations. Fridsma (1971) continued his studies and conducted the model tests in irregular waves. Katayama et al. (2002) also carried out model tests to study the resistance and obtained the drag coefficient for high speed planing craft

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