低亚声速和跨声速矩形柱绕流的大涡模拟研究

摘要

Flow characteristics around a rectangular cylinder with different aspect ratios at low subsonic and transonic speeds were studied by large eddy simulation.At Re =22000,large eddy simulations were per-formed for flows around a rectangular cylinder with aspect ratios of 1∶1,2∶1,3∶1 and 4∶1 at Ma =0.1 and 0.75 respectively,to study the effects of the aspect ratio and the compressibility on the flow characteristics. At Ma=0.1,the Strouhal number decreases first and then increases and finally deceases with the increase of the aspect ratio.Flow reattachment is observed for the cases with aspect ratios of 3∶1 and 4∶1.Complex three-dimensional flow structures were observed in the wake.At Ma =0.75,the Strouhal number and the turbulence intensities decrease with the increase of the aspect ratio.It is also observed that there are two kinds of mechanisms about the formation of the local supersonic zones in the near wake region.%采用基于非结构网格的有限体／有限元混合格式和大涡模拟的方法求解可压缩 Navier-Stokes 方程，研究了不同长宽比矩形柱低亚声速和跨声速绕流的流动特性。在雷诺数为22000时，对来流马赫数等于0．1和0．75，截面长宽比分别为1∶1、2∶1、3∶1和4∶1的矩形柱绕流进行了大涡模拟，以研究长宽比和压缩性对矩形柱绕流流场的影响。马赫数为0．1时，Strouhal 数随着长宽比的增大先降低再增大然后再降低；长宽比为3∶1和4∶1时会有流动的再附产生；柱体上表面的三维特性在长宽比大时更明显。马赫数为0．75时，Strouhal 数随着长宽比的增大逐渐减小；湍流脉动和涡脱落受到抑制；方柱的近尾迹区域，有两种形成机制不同的局部超声速区。