Based on the computational fluid dynamics software FLUENT and the longitudinal motion equation of planning craft crafts, a prediction procedure for coupling and solving of planning craft longitudinal motion response was compiled and the numerical simulation of the dolphin motion of three dimension planning craft model in the uniform flow movement was conducted. According to the different speed and different position of the center of gravity,under the condition of the motion characteristics of the heave and pitch of the planning craft, this paper timely numerically forecasts the boat body amplitude of heave and the angle of trim changing characteristic curve of pitch with time. The results show that, when the longitudinal position of the center of gravity lg=0.231L(L is the length of planning craft), and the volume Froude number Fr▽≥2.7, the dolphin motion of the planning craft appears, and with the increase of the speed, the amplitude of the heave ,the angle of trim and the frequency of the response increase; when Fr▽=5.0, lg=0.381L, 0.351L, the dolphin motion of the planning craft appears, and with the retrusive position of the center of gravity, the amplitude of the heave, the angle of pitching and the frequency of the response increase.

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