扰动形状对钝头体非对称流动的影响

通过在钝头体头部施加人工扰动块可以得到确定的大攻角下的非对称背涡结构。为了研究扰动块形状对非对称背涡结构的影响，本文在攻角50°、雷诺数Re_D=1.54×105的条件下，利用数值模拟对周向角90°、子午角10°的扰动位置的半球形、D型及方形3种扰动块形状分别进行了研究。研究发现在同一扰动位置，半球形扰动主控下的背涡结构为右涡型，而D型扰动和方形扰动主控下的背涡结构呈现左涡型，且方形扰动主控下的背涡结构的非对称性弱于其他2种扰动主控的非对称背涡。通过分析发现扰动块所引起的微流动直接影响钝头体非对称背涡结构。因此为了更精准地通过施加人工扰动得到确定的非对称背涡结构，应尽量选择形状简单、表面平滑过渡的扰动块形状。 

Effects of perturbation geometry on behavior of asymmetric flow over blunt body

The asymmetric vortices can be determined through setting the artificial perturbation on the nose of the blunt body at high angle of attack. To study the influence of perturbation geometry on the asymmetric vortices, numerical simulation was applied and the hemispherical, D-type and square perturbations were set on the position circumferential angle 90° and meridian angle 10° respectively at the angle of attack 50° and Re_D=1.54×10⁵. It is found that the vortex structure induced by hemispherical perturbation is shown as right vortex pattern; however the left vortex pattern is shown for the D-type and square perturbations. What is more, the asymmetry of vortex structure for the square perturbation is weaker than that for the other two perturbations. The reason is that the separated flows from different boundaries of the same perturbation influence each other and affect the asymmetric vortex structure. In order to determine the asymmetric vortices accurately by setting artificial perturbation, the geometry of perturbation should be as simple as possible.