Experiment on interaction of shock and elliptic heavy-gas cylinder by using PLIF
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摘要: 在水平激波管中，采用平面激光诱发荧光(planar laser-induced fluorescence, PLIF)方法对椭圆形重气柱界面的Richtmyer-Meshkov不稳定性进行实验。气柱由SF6混入一定比例的丙酮蒸气构成，环境气体为空气。通过改变椭圆形气柱的长短轴比值，得到了激波马赫数为1.25时，3种初始界面的演化形态。通过相对体积分数标定，得到了界面失稳演化过程中的相对体积分数分布，观察到了激波作用后界面气体聚集、转移、消散等现象。实验结果发现，对于流向轴长与展向轴长之比较大的气柱界面，初始界面产生的涡量更大且分布更广，其界面不稳定性发展得越迅速和剧烈。失稳发展迅速的界面甚至出现涡对碰撞并产生尾部射流结构的现象。初始界面直接决定了失稳发展初期形成的涡对强度和间距，并对后期演化有重要影响。
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关键词:
- Richtmyer-Meshkov不稳定性 /
- PLIF /
- 体积分数场 /
- 气柱 /
- 激波管
Abstract: An experimental investigation of Richtmyer-Meshkov (R-M) instability in the elliptic heavy gas cylinder was presented in detail. The shock-induced instability was studied in a horizontal shock tube using the planar laser-induced fluorescence (PLIF). The gas cylinder surrounded by air was composed of SF6 and acetone vapor. By adjusting the ratio of the long axis to the short one in the gas cylinder was achieved the evolution of three types of initial interface accelerated by a Mach 1.25 shock. After the calibration, concentration map were obtained. Furthermore, the congregation, transfer and dissipation in the concentration field was revealed. With a larger aspect ratio, the gas cylinder has a wider deposition of baroclinic vorticity, resulting in a faster evolution. When the evolution is rapid, a jet occurs in the trail structure due to the collision of the vortex pair. It was demonstrated that the initial configuration directly determines the strength and spacing distance of the vortex pair at early times, thereby exerting a significant influence on the instability evolution at later times.-
Key words:
- Richtmyer-Meshkov instability /
- PLIF /
- concentration field /
- gas cylinder /
- shock tube
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图 3 气柱界面内部气体分布
Figure 3. Distribution of relative volume fraction in the gas cylinder interface
图 5 压力梯度、密度梯度夹角正弦值沿界面半周长的变化
Figure 5. The change of the sine angle of pressure gradient and density gradient along the half perimeter of the interface
图 6 不同形状界面气体相对体积分数分布
Figure 6. Distribution of relative volume fraction of gas at different gas cylinder interfaces
图 7 圆形界面沿轴线的气体相对体积分数分布
Figure 7. Relative volume fraction of gas along axises of circular interface
图 8 界面相对体积分数的概率密度分布
Figure 8. Probability density of interfacial relative volume fraction
图 9 峰值气体相对体积分数与时间关系
Figure 9. Relation between of relative volume fraction peak and time
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