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小扰动界面形态对RM不稳定性影响的数值分析

NUMERICAL STUDY ON THE EFFECTS OF SMALL-AMPLITUDE INITIAL PERTURBATIONS ON RM INSTABILITY

  • 摘要: 采用Navier-Stokes 方程对入射激波及其反射激波连续诱导小振幅扰动界面的Richtmyer-Meshkov 不稳定性增长过程进行了二维数值模拟,分析了单模和随机多模两种不同初始形态的界面上钉结构和泡结构在反射激波作用前后的发展特性. 研究结果发现:单模扰动的初始界面形态对反射激波前、后界面的扰动增长都有影响,反射激波前的界面形态信息可以通过钉和泡结构之间的反转传递到反射激波过后. 扰动界面上钉结构的发展速度控制了界面混合区总体的发展速度,反射激波前界面上发展成具有完整冠部形态的钉,在反射激波后会反转成复杂的泡结构,此泡结构对反射激波后钉的发展不利. 随机多模界面显示了与单模界面类似的发展规律,但随机多模界面上的复杂泡结构分布的不对称性使得其对钉结构增长的拖曳效应相对要弱,这导致了相似扰动波长下多模随机界面的扰动发展相对单模界面扰动发展要快.

     

    Abstract: Two-dimensional simulations of Richtmyer-Meshkov (RM) instability of small-amplitude initial perturbed interface induced by shock waves are performed by using Navier-Stokes equations. The evolution of interface mixing zone, which is considered as a combination of a bubble and a spike before and after the passages of reshock wave, is analyzed under the single-mode and random multi-mode initial perturbed conditions. The results show that the perturbation growth is influenced by the initial patterns of interface before and after the passages of reshock wave. The information of initial perturbed interface pattern can be transmitted to that of the interface after reshock wave by transforming between the bubble and spike. The growth rate of spike on the interface dominates the whole growth rate of the mixing zone. The developed spike with crown shape before the passage of reshock is transformed into the complex bubble structure that drags the development of spike after the passage of reshock wave. The evolution of random multi-mode perturbed interface shows the similar behavior as that of single-mode perturbed interface. However, the asymmetric feature of complex bubble structure on random multi-mode interface weakens the drag effect on the development of spike, and thus gives rise to the faster growth of the random multi-mode interface than that of the single-mode interface, under the conditions of similar initial wave length for both interfaces.

     

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