双椭圆界面Richtmyer-Meshkov流动中的相互干扰效应  

Interaction Effect of Two Ellipse Richtmyer-Meshkov Flows

作　　者：邹立勇[1] 廖深飞 刘金宏[1] 王彦平[1] 柏劲松[1] 谭多望[1] 

机构地区：[1]中国工程物理研究院流体物理研究所冲击波物理与爆轰物理实验室,四川绵阳621999

出　　处：《高压物理学报》2015年第3期191-198,共8页Chinese Journal of High Pressure Physics

基　　金：国家自然科学基金(11172278;11302201;11202195;11472253);中物院科学技术发展基金(2014B0201017)

摘　　要：实验研究了在马赫数为1.18的平面激波冲击作用下,双椭圆界面RichtmyerMeshkov不稳定性演化的动力学过程。椭圆短轴b与入射激波方向垂直,通过改变双椭圆的中心间距d,采用片光高速摄影和PIV(粒子图像测速)技术,观测了4种不同情形的演化模态,获得了界面演化多幅像和700μs时刻的速度场,分析了双椭圆气柱之间的相互干扰效应。当d/b为4.0或3.0时,相互干扰效应较弱,双椭圆气柱演化为两个反向旋转的对涡,速度极大值接近30m/s,出现在2个位置,速度最小值几乎为零,出现在4个位置。当d/b为2.0或1.2时,相互干扰效应很强,两个内涡完全消失,双椭圆气柱演化为一个反向旋转的涡对结构,速度极大值出现在4个位置,速度极小值出现在两个位置。d/b=2.0时,界面演化图像与圆形气柱演化过程类似。相比d/b=2.0的情形,d/b=1.2时产生更大的斜压涡量,界面演化发展更快,后期出现二次涡现象和分叉结构,整体结构类似于单椭圆气柱演化过程。当d/b在2.0~3.0之间变化时,存在一个是否形成两个内涡的非线性临界值。针对双气柱界面演化明显的内涡弱化现象,分析了4种可能的机制。The dynamic evolution process and velocity field of two elliptic heavy-gas(SF6)cylinders accelerated by aplanar shock wave are studied by laser-sheet high-speed photograph and PIV(particle image velocimetry)diagnostics techniques,respectively.The minor axes(b)of the elliptic crosssections are aligned perpendicular to the shock direction.While the cylinder dimensions are fixed,we adjust the center-to-center separation(d)between the cylinders.The flow morphologies are visualized and the interaction effect between cylinders is analyzed.When d/b equals 4.0or 3.0,the two elliptical cylinders roll up into 2counter-rotating vortex pairs and the interaction is weak.The maximal velocity appears at 2positions and its magnitude is close to 30m/s,while the minimal velocity is close to zero and arises at 4positions.When d/b decreases to 2.0or 1.2,due to the strong interaction of the two inner vortices,the inner structure completely disappears and the flow morphology evolves into a countervortex pair.The maximal velocity occurs at 4locations,while the minimal velocity only appears at 2positions.For the d/b=2.0case,the evolving images assemble those of the single circular cylinder except for the small gap in the middle.Compared with the d/b=2.0case,larger amount of baroclinic vorticity is produced in the d/b=1.2case,and the morphology is similar to the single elliptic cylinder case,with a second vortex phenomenon and bifurcation structure occurring at later times.Actually,we observe a nonlinear,threshold-type behavior of inner vortex formation when d/b varies from 2.0to3.0.Finally,we outline and discuss 4possible mechanisms which may lead to the obvious weakening phenomenon of inner vortices.

关 键 词：双椭圆界面 RICHTMYER-MESHKOV不稳定性 高速摄影 粒子图像测速技术 

分 类 号：O354.5[理学—流体力学]