滑移边界对高雷诺钝体绕流流动分离及阻力的影响

Influence of slip boundary on flow separation and drag of flow past bluff body at high Reynolds numbers

[目的]水下航行体附体产生的流动分离会增大航行的阻力与噪声,影响控制面的操纵性能,为此,研究超疏水表面产生的滑移对减阻及流动分离的抑制效果。[方法]建立一种曲面上的部分滑移边界处理方法,并针对有滑移的高雷诺数圆柱绕流和翼型绕流问题进行数值仿真。[结果]结果显示,在高雷诺数下,受滑移边界条件的影响,圆柱绕流会经历湍流卡门涡街、层流卡门涡街和斯托克斯无分离流动3个阶段,阻力系数是先增大后减小,涡脱落频率加快;对于翼型绕流,当滑移长度增大时,分离点的位置逐渐向翼型尾部移动直至流动分离消失,升力系数逐渐增大,阻力系数逐渐减小。[结论]研究表明,滑移边界对高雷诺数钝体绕流有抑制流动分离的作用,减阻效果良好,可为将超疏水材料及表面处理技术应用于水下航行体附体的流动控制提供技术支撑。

[Objectives]Flow separation increases the drag and noise of underwater vehicles, and influences the controllability of their control surfaces. Therefore, the influence of slip caused by superhydrophobic surfaces on drag reduction and flow separation is studied. [Methods]A partial slip boundary condition is developed, and the flow around a circular cylinder and foil with a slip boundary at high Reynolds numbers are numerically simulated. [Results]The results show that the when the slip length increases, the flow around the cylinder goes through three stages: the turbulent Kármán vortex street, laminar Kármán vortex street and non-separation Stokes flow. The drag coefficient increases first and then decreases, and the vortex shedding frequency increases. For flow around a foil, the separation position moves downstream until the separation region disappears when the slip length increases, and the drag coefficient decreases while the lift coefficient increases. [Conclusions]The results of this study show that for flow past bluff body at high Reynolds number, the slip boundary can control flow separation and reduce drag effectively, providing technical support for the application of superhydrophobic surfaces for the flow control of underwater vehicle appendages.