展向具有谐波型扰动的方柱旋涡分离流数值研究

Numerical studies on the ovrtex dynamics in the wake of a square-section cylinder with the spanwise geometric disturbance

基于Fourier谱方法和有限差分的混合方法，对方型截面柱体的分离流及非定常涡动力学进行数值研究，特别是展向具有谐波型几何扰动对流动演化及受力变化的影响。结果表明，当Re=100-150，在未引入扰动的柱体上／下表面处（而非前缘）流动发生局部分离，并形成分离泡。流动分离点随Re数增加是逐渐从后缘前移到前缘附近。沿展向引入扰动后，当Re=100时，在柱体表面产生流向与垂向涡量，甚至抑制了展向涡的发展。当波陡度（波高／波长）为0．167时，产生了类似于发夹涡的结构，此时柱体平均阻力系数和升力系数幅值分别减小了9％和98％。并讨论了相关的机制。

Based on the hybrid method of Fourier spectral and the finite-difference methods, the separated flow and the usteady vortex dynamics about a square-section cylinder is investigated numerically, specially attention is paid on the effect of spanwise disturbance in cylinder geometry on the flow evolution and the forces variation. Results show that, at the case of Re = 100 to 150, the flow around the cylinder without the disturbance is separated locally on the up/down sides, not the leading edge, to form Separated bubble. The separation point is moved from the trailing edge to the position near the leading edge with the leading edge with the increasing of Reynolds number. After the disturbance is introduced, at the Reynolds number of 100, streamwise and vertical vorticities are produced on the cylinder surfaces, leading to the suppression of spanwise vortex shedding. When the wavyness is up to 0. 167, the hairpin-like vortex structure is emerged, and then the timeaveraged drag coefficient and the amplitude of lift coefficient are reduced 9 % and 98 %, respectively. The mechanism related is discussed.