ABSTRACT

The double M-craft is a new type of high performance ship which combines the gliding characteristics of conventional planing craft and the use of air to generate lift similar to hovercraft to reduce drag. However, most of the researches on double M-craft are based on model experiment method, and the theoretical research is limited to resistance and sailing mode prediction. Fewer researchers have analyzed the motion of double M-craft in waves, because it is difficult to simulate waves in CFD, and the craft has higher speed and more complex motion. Because of the complex change of the craft's navigation state and the influence of water-gas two-phase flow, it is not suitable to use the potential flow method to simulate. Based on the viscous theory and overlapping grid technology, the VOF method is used to capture the water-gas two-phase flow field. The 6-DOF motion of a rigid body is simulated by DFBI. The pitch and heave motions of a double M-craft under head waves are numerically simulated. Reliability of background grid case is proved by wave decay and waveform verification. Then, the independency of grid is discussed through uncertainty analysis, and the appropriate overset grid case is selected. Different speeds (Fr=1.2, 2.4, and 3.6) under head wave are selected as calculation conditions to obtain the motion responses of double M-craft in waves. The accuracy of numerical simulation is proved by comparing with experimental values. Compared with the motion response of the conventional planing craft with same displacement, the results show that the double M-craft has better seakeeping performance.

INTRODUCTION

The M-hull is a kind of M-yacht originated from the Venice River. It combines the advantages of conventional planing boat and hovercraft, and achieves wave elimination and drag reduction only by its unique shape advantages. There are good prospects for both civilian and military use. The "Stiletto" is a successful case of transformation on the basis of the M-type yacht.

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