钝体矩形断面绕流场机理与主分量分析

为研究钝体矩形断面的绕流场特征和气动特性,针对宽高比为4的矩形断面,基于雷诺时均N-S方程和SSTk-ω湍流模型开展了断面绕流场非定常CFD模拟,得到了与其它文献报道一致的断面阻力系数、涡脱St数、上下面压力平均值和脉动值分布、平均涡脱位置和再附长度.对表面脉动压力时程的主分量分析表明,第一主分量与压力脉动RMS分布一致,能反映表面不同位置的脉动压力强弱和整体分布特征.基于上下面第一阶主分量形状,可确定其分离剪切流中主漩涡的脱落位置.基于第一阶主分量系数,可获得矩形断面绕流的涡脱频率.矩形断面上下表面的主漩涡脱落主导了上下表面的压力脉动特征.

Flow Mechanisms around Bluff Rectangular Cylinders and Its Principle Component Analysis

The flow field around a rectangular cylinder with an aspect ratio of 4 was simulated with Reynolds-averaged Navier-Stokes equations combined with SST k-ω turbulent models,which helped to represent its flow structures and aerodynamic characteristics.The results obtained,including drag coefficient,Strouhal number,mean and fluctuating pressure distribution on cylinder surfaces,averaged vortex shedding location and reattachment length,agreed well with available reports.Through the application of the Principle Component Analysis(PCA) to records of fluctuating pressure on the surfaces,it is found that the first principle component shares the same trends with the RMS distribution of fluctuating pressure,which may be an alternative way to characterize the fluctuating pressure.Based on the configuration of the first principle component,the vortex shedding location on the side surface can be readily located,and the vortex shedding frequency can also be obtained from the coefficients of the first principle.It is highlighted that the main vortex shedding on the side surfaces dominates the features of the fluctuating pressure.