双断级滑行艇水动力特性数值研究

Numerical simulation on hydrodynamic performances of double-stepped planing boat

基于CFD方法对某双断级滑行艇在不同航速下的绕流场进行了数值模拟,通过与试验值的对比验证了数值方法的可行性,结合试验中航态的变化研究了断级后空穴产生机理、艇底湿表面、压力分布及各滑行面的负荷系数.数值模拟结果表明:断级后低压区是空穴形成的直接原因,空穴核心区域以气相为主,外围则为水气混合物;空穴的存在减少了断级后的浸湿面积,并导致艇底压力的阶跃式变化;当容积弗劳德数Fr>2.63时,驻点线与艏部第一断级相交,导致该断级后部出现较大的浸湿面,在设计中应予以避免;在滑行阶段,第二断级后滑行面提供大部分的升力,其最大负荷系数为0.67.

Numerical simulation of a double stepped planing boat model at different Froude number was carried out by computational fluid dynamics method in this paper and the feasibility of this method was verified by comparison with experimental data.The air cavity mechanism,wet surface,pressure distribution and load coefficient of planing surfaces were investigated combined with the experimental trim and heave.The simulation results have shown that the main cause of air cavity formed is the negative pressure area behind step,the core region of air cavity is purely air and the outer is air-water two-phase flow.The air cavity causes the reduction of wetted surface and the step type change of pressure distribution.It should be avoid during designing that the stagnation line crossing step when Froude number is greater than 2.63 for the increasing wetted surface.At planing speeds,planing surface behind the second step supports most of the hull weight,and the maximum load coefficient is up to 0.67.