带自由液面有限长圆柱绕流数值模拟

目的]为了探究自由液面及自由端对典型钝体绕流问题的影响,对带自由液面的有限长圆柱绕流进行研究。方法]基于延时分离涡模拟(DDES)技术和分段线性界面重构(PLIC)方法,利用自主开发的naoe-FOAM-SJTU求解器开展数值模拟。结果]结果显示,自由液面和自由端的存在增大了局部位置的升、阻力,推迟了圆柱表面流动分离的发生;相较于深吃水位置,自由液面附近流向的速度"恢复"延缓,横向的速度呈向外运动的趋势;自由液面的变形产生了大量细碎的漩涡,自由端的卷拧状漩涡在一定程度上抑制了卡门涡街的发展。结论]研究表明,目前采用的数值方法能够准确捕捉复杂流场,同时,自由液面和自由端的存在将显著改变流场沿吃水方向的分布。

Numerical simulation of flows around a finite-length cylinder with free surface

Objectives]In order to explore the influence of the free surface and free end on the flow field around typical bluff bodies,the flow field around a finite-length cylinder with a free surface is studied.Methods]Based on the delay detached-eddy simulation(DDES)approach and piecewise linear interface calculation(PLIC)method,our in-house solver naoe-FOAM-SJTU is adopted to carry out numerical simulations.Results]The results show that the existence of the free surface and free end increases the lift and drag of local positions,and delays the occurrence of flow separation on the cylinder’s surface.Compared with the deep draft region,the recovery of streamwise velocity near the free surface is delayed,and the transverse velocity tends to move outward.The deformation of the free surface generates many small vortices,and the twisted vortex at the free end restrains the development of the Kármán vortex street to a certain extent.Conclusions]This study shows that the current numerical methods can accurately capture this complex flow field.At the same time,the existence of the free surface and free end significantly changes the distribution of the flow field in the draft direction.