激波冲击SF_6重气泡引发射流的数值模拟

Simulation on jet formation induced by interaction of shock wave with SF_6 bubble

为深入研究重气泡内激波聚焦和射流生成的机理,采用高精度计算格式和高网格分辨率对马赫数为1.23的平面入射激波与SF_6重气泡的作用过程进行数值模拟,计算结果与文献中实验吻合较好。结果显示:入射激波在重气泡内首先在流向上汇聚形成上、下对称的高压区,随后,这对高压区在SF_6重气泡中心对称轴处再次碰撞,完成激波聚焦过程,并在气泡下游界面附近形成远大于初始压力和密度的局部高压高密度区,体现出SF_6重气泡极强的聚能效应;激波聚焦还引起气泡下游界面附近的涡量变化,涡对的旋转能够加速射流形成与发展。因此,SF_6重气泡下游界面附近的高压区和涡量分布对形成射流结构均有促进作用。

To better understand the mechanisms governing the shock focusing and jet formation,we simulated the interaction between the planar incident shock wave of the Mach number 1.23 and the SF_6 heavy gas bubble using the high resolution computation schemes and grid. The numerical results are consistent with the experimental results of the reference. It was found that the incident shock wave converges along the streamwise direction inside the gas bubble,and forms a pair of longitudinally symmetrical high pressure regions,which then collide in the central symmetrical axis where the shock focusing is completed. The shock focusing forms a local region with high pressure and density,considerably larger than the initial pressure and density. Its peak pressure exceeds by far the normal atmospheric pressure,implying that the SF6 heavy gas bubble has a strong cumulative energy effect. Simultaneously,the shock focusing also induces vorticity variation near the downstream interface of the gas bubble,and the rotation of the vortex pair accelerates the jet formation and development.Hence,both the high pressure region and the vorticity distribution near the downstream gas interface promote the formation of the jet.