圆柱后方柔性分离盘的尾流诱导响应模拟研究

Wake-Induced Vibration of Flexible Splitter Plate Attached to Rear Point of Circular Cylinder

该文基于preCICE开源耦合库,将OpenFOAM-9和deal.ii分别作为流体域和固体域求解模块,结合有限体积法(FVM)和有限元法(FEM)对低雷诺数(Re=160)圆柱背流侧柔性分离盘的尾流诱导响应进行模拟研究,剖析了不同盘长(L/D=2.0~4.0)和无量纲弹性模量(E^(*)=100~5 000)对分离盘动态响应的影响。结果表明:柔性分离盘的摆动变形受盘长和弹性模量的共同控制。圆柱表面分离的边界层在圆柱后方卷曲后,沿分离盘表面迁移,形成的低压区导致柔性分离盘出现周期性变形,最终剪切层被盘尖的摆动切断而脱落。随着盘长的增大,沿分离盘表面出现的局部旋涡数量增多,激发出更高阶的摆动响应。根据柔性分离盘的摆动阶数及是否存在分叉现象(对称破裂),将摆动模式分为五种:对称-Ⅰ型、对称-Ⅱ型、分叉-Ⅰ型、分叉-Ⅱ型和对称-Ⅲ型。分叉作为对称-Ⅰ型和对称-Ⅱ型的过渡模式,其摆动幅度骤降。相较于裸柱,一定刚度范围内的柔性分离盘降低了整体结构的阻力及涡脱频率,但在所研究的刚度范围内,其抑制效果低于刚性分离盘。

In this paper,the flow past a flexible splitter plate attached behind a rigid circular cylinder is numerically investigated at a low Reynolds number of 160.As a two-way Fluid-Structure Interaction(FSI)issue,the simulation is conducted using the preCICE open source coupling library with OpenFOAM-9 and deal.i as the fluid domain and solid domain solving modules,respectively.The finite-volume method(FVM)and finite-element method(FEM)are utilized to solve fluid and solid motion equations,respectively.The effects of the plate length(L/D=2.0-4.0)and non-dimensional Young's modulus(E^(*)-100-5000)on the vibration response and flow structure are systematically examined.Numerical results indicate that the vibration response of the flexible plate depends on both L/D and E^(*).The boundary layer separated from the surface of the cylinder curls behind the cylinder,and migrates along the surface of the spliter plate,forming low-pressure areas that cause periodic deformation of the flexible splitter plate.Finally,the shear layer is cut off by the plate tip and hence the formation of the vortex.As the plate length increases,the number of local vortices appearing along the surface of the spliter plate increases,contributing to the higher-order vibration response.According to the vibration order and whether there is bifurcation phenomenon(symmetry breaking),five vibration modes are identified:symmetry-,symmetry-II,symmetry-Il,bifurcation-I and bifurcation-I mode,respectively.Bifurcation,as a transitional mode between the symmetry-I and symmetry-Il,has a sudden decrease in the vibration amplitude.Compared to a bare cylinder,the flexible splitter plate within a certain stiffness range reduces the drag and vortex shedding frequency of the overall structure,but their suppression effect is weaker than that of the rigid plate within the stiffness range studied.