低雷诺数下圆柱强迫振动特性光滑粒子流体动力学模拟

SPH simulation of flow past an oscillating cylinder at low Reynolds number

基于光滑粒子流体动力学(SPH)方法,开发了能够准确描述水流作用下圆柱强迫振动特性的数学模型。通过引入适合于无网格粒子法的开边界算法,来模拟出入流边界条件,建立了具有造流功能的SPH数值水槽。圆柱及计算域的上下边界均采用修正的动力边界条件进行模拟。借助于粒子位移矫正和压力修正算法,避免了圆柱周围流体粒子压力大幅震荡以及结构下游区域出现空腔等非物理性现象。使用典型的圆柱绕流数据,验证了所建SPH模型的计算性能,研究了固定圆柱在低雷诺数情况下的尾涡脱落模式和升阻力变化规律。明确了低雷诺数下强迫振动圆柱在频率锁定以及非锁定区间内的升力变化规律,量化了升力与外界激励频率之间的关系。

A numerical flume is developed based on the smoothed particle hydrodynamics(SPH)method to study the cylinder motions under the fluid flows at low Reynolds number.The inlet and outlet boundaries are imposed by introducing the open boundary algorithm.The cylinder surface and the upper and lower boundaries of the computational domain are discretized by the improved dynamic boundary conditions.The non-physical phenomena such as the cavity in the wake area of the cylinder and the large pressure oscillations of the surrounding fluid particles are avoided by means of the particle displacement and pressure correction algorithms.The lift and drag force coefficients and the wake vortex shedding mode of the fixed cylinder are analysed under the different Reynolds numbers.The numerical results show that the Strouhal frequency,the lift and drag force coefficients are well consistent with the available reference data.Numerical simulations are then performed for flow past a forced oscillations cylinder.The lift force characteristics of the forced cylinder and its relationship with the external excitation frequency are studied both in the lock-in and non-lock-in frequency zones.