中文摘要：

采用粒子图像测速（PIV）技术,实验研究了激波两次冲击空气环境中重气体SF6气柱的Richtmyer-Meshkov（RM）不稳定性,定量表征了流场的速度、涡量和环量。结果表明,激波首次冲击气柱后,界面演化成初始涡对,且在较长时间内涡强度的变化很小。激波二次冲击气柱后：当反射距离较小时,界面衍生出二次涡对,其旋转方向与初始涡对的旋转方向相反,强度显著小于初始涡对的强度;当反射距离较大时,则不衍生大尺度涡结构。初始涡对的环量在激波二次冲击气柱后随时间逐渐减小,说明能量逐渐由流场中的大尺度结构转移至小尺度结构。利用PIV技术得到的初始涡对和二次涡对的环量与理论模型的预测结果吻合较好。

英文摘要：

The Richtmyer-Meshkov （RM） instability in a twice-shocked heavy gas （SF6） cylinder surrounded by ambient air is experimentally studied using the particle image velocimetry （PIV） technique,and the velocity and vorticity fields as well as the circulation of the flow are quantitatively characterized. The results show that after the first shock-interface interaction, the evolution of the interface is dominated by the formation of a primary vortex pair, whose strength undergoes little change over a relatively long time; but after a reshock, for a short endwall distance,a secondary vortex pair,with its rotation opposite to the primary vortex pair, is formed whose strength is significantly weaker than that of the primary vortex pair,while, for a long endwall distance, no large scale vortex structure is formed. The circulation of the primary vortex pair decreases over time after the reshock, which suggests that the energy is being transferred from the large scale structures to the smaller ones in the flow. The circulations of the primary and secondary vortex pairs are remarkably consistent with the predictions by the theoretical models.