基于均布式多孔表面吹气的索结构尾流控制

Control of Wakes of Cable Structures Based on Blowing through Uniformly Distributed Porous Surfaces

为研究基于均布式多孔表面吹气对索结构尾流的控制效果,进行了一系列的风洞试验.通过粒子图像测速(PIV)系统对雷诺数Re为1.0×10^(4)的无控和控制工况的索结构尾流场进行了测量,分析了尾流的瞬时和时均流动特性,并利用本征正交分解(POD)和动态模态分解(DMD)对降阶后的模态特性进行了分析和对比.在吹气控制中,控制参数为无量纲的等效吹气系数C_(Q).研究结果表明:随着C_(Q)的增加,POD各模态的能量分布趋于一致,流场中的拟序结构尺度趋于均一化,对旋涡脱落起控制作用的第1、2阶模态受到抑制;尾流中旋涡脱落频率被改变,分离的剪切层间的相互作用得到削弱;多个DMD模态特征值被改变,模态幅值的频域分布发生偏移;尾流中回流区的尺度变大,湍动能和雷诺应力得到显著削弱.

In order to investigate the control effects on a cable structure based on blowing through uniformly distributed porous surfaces,we conducted a series of wind tunnel tests.The measurements of wake flow fields of the cable structure under the uncontrolled and controlled cases with Reynolds number Re 1.0×10^(4) were achieved by a PIV system.Instantaneous and time-averaged flow characteristics was analyzed,and proper orthogonal decomposition(POD)and dynamic mode decomposition(DMD)were utilized to analyze step-down modal characteristics.The non-dimensional control parameter in the blowing control was the equivalent blowing coefficient,C_(Q).The experimental results show that with the increase of C_(Q),POD modal energy distributions tend to be uniform,dimensions of coherent structures in the global flow fields are transformed to be homogeneous and the dominance of the first two POD modes is restrained.The wake vortex shedding frequency is changed and interactions between separated shear-layers are restricted.DMD modal eigenvalues are changed and spectral distributions of mode amplitudes shifted.Furthermore,the recirculation region dimension in the wake is enlarged and the turbulence kinetic energy and Reynolds shear stress are significantly weakened.