Shock flame interactions are fundamental problems in many combustion applications ranging from flame acceleration to flame control in supersonic propulsion applications. The present paper seeks to quantify the rate of deformation of the flame surface and burning velocity caused by the interaction and to clarify the underlying mechanisms. The interaction of a single shock wave with a cellular flame in a Hele-Shaw shock tube configuration was studied experimentally, numerically, and theoretically. A mixture of stoichiometric hydrogen-air at sub-atmospheric pressure was chosen such that large cells can be isolated and their deformation studied with precision subsequent to the interaction. Following passage of the incident shock and vorticity deposition along the flame surface, the flame cusps are flattened and reversed backwards into the burnt gas. The reversed flame then goes through four stages. At times significantly less than the characteristic flame burning time, the flame front deforms as an inert interface due to the Ricthmyer-Meshkov instability with non-linear effects becoming noticeable. At times comparable to the laminar flame time, dilatation due to chemical energy release amplifies the growth rate of Ricthmyer-Meshkov instability. This stage is abruptly terminated by the transverse burnout of the resulting flame funnels, followed by a longer front re-adjustment to a new cellular flame evolving on the cellular time scale of the flame. The proposed flame evolution model permits to predict the evolution of the flame geometry and burning rate for arbitrary shock strength below the shock-induced auto-ignition point and flames with unit Lewis number in two-dimensions.
Nonlinear Richtmyer--Meshkov instability and mixing transition induced by a Mach 1.45 shock and subsequent re-shock at an interface between two ideal gases (sulfur hexafluoride and air) with high Atwood number are studied with second-moment analysis using data from high-resolution compressible Navier--Stokes simulations. The analysis first addresses the importance of two second-order moments: turbulent mass flux and density-specific-volume covariance, together with their transport equations. These quantities play an essential role in the development of Favre-averaged Reynolds stress and turbul…
The Richtmyer-Meshkov (RM) instability has long been an interesting subject due to its fundamental significance in scientific research, as well as its crucial role in engineering applications. In this study, the contribution of shock Mach number on the evolution of the RM instability induced by a shock-accelerated square light bubble is investigated numerically. The square bubble is composed of helium gas and the surrounding (ambient) gas is nitrogen. Three cases of incident shock strength are considered: Ms = 1.21, 1.7, and 2.1. An explicit mixed-type modal discontinuous Galerkin scheme with …
The classical Richtmyer-Meshkov instability is a hydrodynamic instability characterizing the evolution of an interface following shock loading. In contrast to other hydrodynamic instabilities such as Rayleigh-Taylor, it is known for being unconditionally unstable: regardless of the direction of shock passage, any deviations from a flat interface will be amplified. In this article, we show that for negative Atwood numbers, there exist special sequences of shocks which result in a nearly perfectly suppressed instability growth. We demonstrate this principle computationally and experimentally wit…
Passive freeze-out of the Richtmyer-Meshkov instability
Imperial College London（帝国理工学院）；Lawrence Livermore National Laboratory（劳伦斯利弗莫尔国家实验室）；ESRF - The European Synchrotron（欧洲同步辐射装置）；Technion–Israel Institute of Technology（以色列理工学院）；First Light Fusion Ltd.（第一束聚变有限公司）
Lawrence Livermore National Security, LLC（劳伦斯利弗莫尔国家安全有限责任公司）；Lawrence Livermore National Laboratory（劳伦斯利弗莫尔国家实验室）
Richtmyer-Meshkov Instability (RMI) is a complicated phenomenon that occurs when a shockwave passes through a perturbed interface. Over a thousand hydrodynamic simulations were performed to study the formation of RMI for a parameterized high velocity impact. Deep learning was used to learn the temporal mapping of initial geometric perturbations to the full-field hydrodynamic solutions of density and velocity. The continuity equation was used to include physical information into the loss function, however only resulted in very minor improvements at the cost of additional training complexity. Pr…
We study the Richtmyer--Meshkov (RM) instability of a relativistic perfect fluid by means of high order numerical simulations with adaptive mesh refinement (AMR). The numerical scheme adopts a finite volume Weighted Essentially Non-Oscillatory (WENO) reconstruction to increase accuracy in space, a local space-time discontinuous Galerkin predictor method to obtain high order of accuracy in time and a high order one-step time update scheme together with a "cell-by-cell" space-time AMR strategy with time-accurate local time stepping. In this way, third order accurate (both in space and in time) n…
Bridging the local and the global: a physically constrained buoyancy--drag model for unified prediction of Rayleigh--Taylor and Richtmyer--Meshkov mixing widths across density ratios
College of Mechanical and Electrical Engineering, Beijing University of Chemical Technology（北京化工大学机电工程学院）；Institute of Applied Physics and Computational Mathematics（应用物理与计算数学研究所）；National Key Laboratory of Computational Physics（计算物理学国家重点实验室）；Center for Applied Physics and Technology, HEDPS, College of Engineering, Peking University（北京大学工程与应用物理与技术中心）
In the present paper, an efficient method to generate "pure" cylindrically converging shock wave without a following contact surface is proposed firstly. Then, the Richtmyer-Meshkov instabilities of two interfaces driven by the generated cylindrically converging shock wave and the associated fluids' mixing behaviors are numerically studied. The results show that the instability of the interface is characterized by the growth of perturbation amplitude before re-shock. However, the mixing of fluids is enhanced dramatically after re-shock, which is manifested not only by the evolutions of flow st…
