Viscous flows around ship hull is of great complexity, and when the ship is advancing with drift angles, the flow field can be more complicated. In this paper, the viscous flow field around an obliquely towed surface combatant DTMB 5512 is computed using the unsteady Reynolds-averaged Navier–Stokes (URANS) method. The numerical simulations are carried out by the in-house CFD solver naoe-FOAM-SJTU, which is developed on the open source platform OpenFOAM. To refine local grids and simulate dynamic ship motions, the overset grid approach is applied. Grid convergence study is first performed at straight-ahead towed condition with three sets of grid number and the results show monotonically convergence. Six different drift angles for the DTMB 5512 model at Froude number of 0.28 are simulated and the predicted hydrodynamic forces and flow field are presented. During the simulation, the ship hull is free to trim and sinkage at a free surface environment. As for straight-ahead towed condition, the total resistance coefficient and flow field, i.e., wave pattern and wake region, between this work and the experiment are compared. Both force coefficients and flow field show good agreement with the available experimental data. For oblique towed conditions, the lateral force, yaw moment and the derived hydrodynamic derivatives are also presented and compared with the experimental results. The variation of wave pattern and wake region at different drift angles are presented and analyzed. The results show that the current approach can be an effective tool to predict the viscous flows and hydrodynamic loads for oblique towed ships.

中文翻译：

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使用重叠网格对不同漂移角表面战斗模型周围粘性流动的数值模拟

船体周围的粘性流动非常复杂，当船舶以偏角前进时，流场会更加复杂。在本文中，使用非定常雷诺平均 Navier-Stokes (URANS) 方法计算倾斜拖曳水面战舰 DTMB 5512 周围的粘性流场。数值模拟由在开源平台 OpenFOAM 上开发的内部 CFD 求解器 naoe-FOAM-SJTU 进行。为了细化局部网格并模拟动态船舶运动，应用了重叠网格方法。网格收敛性研究首先在三组网格数的直线牵引条件下进行，结果显示单调收敛。DTMB 5512 模型在弗劳德数为 0 时的六种不同漂移角。对 28 进行了模拟，并给出了预测的水动力和流场。在模拟过程中，船体可以在自由表面环境下自由纵倾和下沉。对于直行拖曳工况，比较了本文与实验的总阻力系数和流场，即波型和尾流区。力系数和流场都与现有的实验数据显示出良好的一致性。对于倾斜拖曳条件，还给出了侧向力、偏航力矩和推导的水动力导数，并与实验结果进行了比较。给出并分析了不同漂移角下波型和尾流区的变化规律。