线性剪切来流下串列双方柱绕流特性的数值模拟

为揭示线性剪切来流对串列双方柱绕流特性的影响，基于多步格式的特征线算子分裂有限元法，在计算域出口处采用对流边界条件，建立线性剪切来流的方柱绕流数值模型。对剪切参数为0~0.4的不同间距比下串列双方柱绕流数值模拟，结果表明:剪切来流可以抑制涡漩脱落，降低斯特劳哈数；上游方柱驻点随剪切参数的增加向高速侧移动，当剪切参数大于0.3时驻点的位置不再发生变化。进一步通过对比剪切参数分别为0和0.1的模拟结果发现:串列双方柱间隙内流场有无涡脱产生与该区域内水平方向时均速度场为负的区域是否连续有关；间距比和剪切参数通过改变方柱周围的速度场对作用于方柱表面的压力产生较大影响，迎流面与背流面的压力差剧增导致方柱平均阻力系数剧增。

Numerical study of the characteristics of linear shear flow past two square cylinders in tandem arrangement

The convective outflow boundary condition is used in the multistep characteristic-based operator-splitting(MCBOS) finite element method. A numerical model for linear shear flow past square cylinders in tandem arrangement is established. The model is proven feasible through the simulation of the linear shear flow past isolation square cylinder. Effect of the shear parameter and spacing ratio has been studied. The numerical results show that the shear flow can suppress vortex shedding and decrease the S_r number. The stagnation point of the upstream square cylinder shifts toward the lateral separation point. When shear parameter is equal or greater than 0.3, the location of the stagnation point remains unchanged. The results also show that the wake field of the gap of two tandem square cylinders changes from the steady state to the unsteady state without vortex shedding and then to the unsteady state with vortex shedding as the spacing ratio increases. The reason for this in deeply connects with the continuous negative value. The dramatic increase in the pressure difference between stoss and lee side leads to increased the mean drag coefficient abruptly.