复杂外形潜水器旋转水动力的计算

Rotational Hydrodynamic Calculation of Complex-Shaped Underwater Vehicle

复杂外形的潜水器动力学模型是高度非线性且耦合的,很难精确建立.为提高潜水器艏向控制性能,通过计算流体力学(CFD)方法来计算复杂外形无人遥控潜水器(ROV)在回转过程中所受的阻尼力/力矩,以获取回转运动的水动力系数,从而提高回转动力学建模精度.从如下两个方面对现有方法进行了改进:(1)采用重叠网格方法替代动网格方法,解决网格运动过程中质量下降的问题,避免了网格单元出现负体积;(2)结合移动参考坐标系和重叠网格两种方法求解ROV的旋转水动力,可加快收敛速度,提高重叠网格非稳态计算的可信度.采用由CFD计算得到的水动力系数构建ROV的动力学模型并基于该模型进行回转控制数值模拟,计算结果与ROV在水池中的回转控制实验结果吻合较好,从而间接验证了所提方法的有效性.

Accurate dynamics of complex-shaped remotely operated vehicle(ROV)is hard to model.To improve the performance of heading control system and identify the hydrodynamic coefficients of the rotary motion,damping force and torque are calculated by CFD methods.The approach differs from existing CFD methods in:(1) overset method is applied instead of moving reference frame method to maintain quality of moving meshes and avoid negative volume of grid elements;(2) moving reference frame and overset methods are combined to calculate the rotational hydrodynamic force to accelerate the convergence rate and improve reliability of CFD simulations.To validate the proposed approach,the rotational dynamic model for an ROV is built in terms of the CFD-based hydrodynamic coefficients and then simulated under rotating control commands.The calculation results agree well with the tank tests of real underwater vehicle under the same control commands and thus verify the effectiveness of the proposed approach indirectly.