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Convergent Richtmyer-Meshkov instability on two-dimensional tri-mode interfaces

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Science China(Physics,Mechanics & Astronomy) 2024年第12期67卷 106-118页

作者： Zhigang Zhai Jinru Xu xisheng luo Advanced Propulsion Laboratory Department of Modern MechanicsUniversity of Science and Technology of ChinaHefei230026China State Key Laboratory of High Temperature Gas Dynamics Institute of MechanicsChinese Academy of SciencesBeijing100190China

Interfacial fluid mixing driven by a shock wave is a common phenomenon that occurs frequently in basic science research and in a variety of *** this work,shock-tube experiments on the developments of two-dimensional tri-mode interfaces accelerated by a convergent shock wave are *** sets of different combinations in the value of phase and that of amplitude in a tri-mode perturbed interface are studied to evaluate the effect of mode coupling on the amplitude growths of the basic *** qualitative results show that the phase combination obviously affects the interface morphologies and flow *** alternation of each mode amplitude does not affect the major flow features,such as the number and arrangement of the bubbles and spikes,but affects the local interface *** upon the phase combination,the mode amplitude growth is either promoted or suppressed by mode coupling relative to the single-mode *** considering the feedbacks from both the first-order and second-order mode couplings,the mode amplitude growth can be qualitatively *** to dual-mode interface,mode coupling occurs earlier in tri-mode *** the sets of parameters we studied,the effect of initial phase on the amplitude growth is greater and occurs earlier for the mode with low mode *** addition,the amplitude development of mode with high mode number is more affected by initial amplitudes of basic modes than that of mode with low mode *** introduction of the third mode affects the amplitude growths of original two modes,but has little effect on the final mixing width ***,a theoretical model is proposed to predict the amplitude growth of each basic mode.

关键词： convergent shock wave tri-mode interface mode-coupling

Interaction of strong converging shock wave with SF6gas bubble

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Science China(Physics,Mechanics & Astronomy) 2018年第6期61卷 75-83页

作者： Yu Liang ZhiGang Zhai xisheng luo Department of Modern Mechanics University of Science and Technology of China

Interaction of a strong converging shock wave with an SF6 gas bubble is studied, focusing on the effects of shock intensity and shock shape on interface evolution. Experimentally, the converging shock wave is generated by shock dynamics theory and the gas bubble is created by soap film technique. The post-shock flow field is captured by a schlieren photography combined with a high-speed video camera. Besides, a three-dimensional program is adopted to provide more details of flow field. After the strong converging shock wave impact, a wide and pronged outward jet, which differs from that in planar shock or weak converging shock condition, is derived from the downstream interface pole. This specific phenomenon is considered to be closely associated with shock intensity and shock curvature. Disturbed by the gas bubble, the converging shocks approaching the convergence center have polygonal shapes, and the relationship between shock intensity and shock radius verifies the applicability of polygonal converging shock theory. Subsequently, the motion of upstream point is discussed, and a modified nonlinear theory considering rarefaction wave and high amplitude effects is proposed. In addition, the effects of shock shape on interface morphology and interface scales are elucidated. These results indicate that the shape as well as shock strength plays an important role in interface evolution.

关键词： converging shock wave gas bubble experiment numerical simulation

Effect of Atwood number on convergent Richtmyer-Meshkov instability

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Acta Mechanica Sinica 2021年第3期37卷 434-446,I0002页

作者： Jinggang Tang Fu Zhang xisheng luo Zhigang Zhai Department of Modem Mechanics University of Science and Technology of ChinaHefei 230026China Beijing Institute of Space Long March Vehicle Beijing 100076China

Developments of two-dimensional single-mode light/heavy interfaces driven by convergent shock waves are numerically investigated,focusing on the effect of the Atwood number on the Rayleigh-Taylor stabilization,the compressibility and the *** different test gases,including C〇2,Kr,R22,R12 and SF6,are considered with air as the ambient *** is clarified for the first time that the unperturbed interface begins to decelerate when the shock focuses at the convergence center,and the acceleration during the deceleration phase is proportional to the Atwood *** the first reshock,the interface moves outwards with a deceleration until it starts moving *** the initial interface is weakly disturbed,a more obvious amplitude reduction is observed for the case with a larger Atwood number before the reshock,which means that the Rayleigh-Taylor stabilization is *** assess the effect of the Atwood number on the compressibility and the nonlinearity,three models,including a linear incompressible model,a nonlinear incompressible model and a linear compressible model,are adopted to predict the amplitude growth before the *** results show that the nonlinearity is weak,and is almost not influenced by the Atwood number before the *** compressibility,however,greatly changes the amplitude *** the Atwood number increases,the compressibility plays a less significant role in the amplitude growth because a heavier gas is harder to be *** a gas with a larger specific heat ratio is also difficult to be compressed,the specific heat ratio plays a minor role to the compressibility relative to the Atwood *** the reshock,the amplitude grows linearly until the nonlinearity in the cases with large Atwood numbers is strong enough to reduce the amplitude growth rate.

关键词： Atwood number Convergent shock wave Richtmyer-Meshkov instability Rayleigh-Taylor effect Compressibility

Numerical study on shock-dusty gas cylinder interaction

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Acta Mechanica Sinica 2019年第4期35卷 740-749页

作者： Jingyue Yin Juchun Ding xisheng luo Xin Yu Beijing Institute of Applied Physics and Computational Mathematics Beijing 100094 China Advanced Propulsion Laboratory Department of Modern Mechanics University of Science and Technology of China Hefei 230026 China

The interaction of a planar shock wave with a dusty-gas cylinder is numerically studied by a compressible multi-component solver with an adaptive mesh refinement technique. The influence of non-equilibrium effect caused by the particle relaxation, which is closely related to the particle radius and shock strength, on the evolution of particle cylinder is emphasized. For a very small particle radius, the particle cloud behaves like an equilibrium gas cylinder with the same physical properties as those of the gas-particle mixture. Specifically, the transmitted shock converges continually within the cylinder and then focuses at a region near the downstream interface, producing a local high pressure zone followed by a particle jet. Also, noticeable secondary instabilities emerge along the cylinder edge and the evident particle roll-up causes relatively large width and height of the shocked cylinder. As the particle radius increases, the flow features approach those of a frozen flow of pure air, e.g., the transmitted shock propagates more quickly with a weaker strength and a smaller curvature, resulting in an increasingly-weaken shock focusing and particle jet. Also, particles would escape from the vortex core formed at late stages due to the larger inertia, inducing a greater particle dispersion. It is found that a large particle radius as well as a strong incident shock can facilitate such particle escape. The theory of luo et al.(J. Fluid Mech., 2007) combined with the SZ circulation model ( J. Fluid Mech., 1994) can reasonably explain the high dependence of particle escape on the particle radius and shock strength.

关键词： Dusty-gas cylinder Non-equilibrium effect Shock wave Instability

Mode coupling in converging Richtmyer-Meshkov instability of dual-mode interface

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Acta Mechanica Sinica 2020年第2期36卷 356-366页

作者： Zhangbo Zhou Juchun Ding Zhigang Zhai Wan Cheng xisheng luo Advanced Propulsion Laboratory Department of Modern MechanicsUniversity of Science and Technology of ChinaHefei 230026China Mechanical Engineering Physical Science and Engineering DivisionKing Abdullah University of Science and TechnologyThuwal 23955-6900Saudi Arabia

The converging Richtmyer-Meshkov(RM)instability on single-and dual-mode N2/SF6 interfaces is studied by an upwind conservation element and solution element *** unperturbed case is first considered,and it is found that the shocked interface undergoes a long-term deceleration after a period of uniform *** evolution of single-mode interface at the early stage exhibits an evident nonlinearity,which can be reasonably predicted by the nonlinear model of Wang et al.(Phys Plasmas 22:082702,2015).During the deceleration stage,the perturbation amplitude drops quickly and even becomes a negative(phase inversion)before the reshock due to the Rayleigh-Taylor(RT)*** the reshock,the interface experiences a phase inversion again or does not,depending on the reshock *** growth of the second-order harmonic in the deceleration stage clearly reveals the competition between the RT effect and the *** dual-mode interfaces,the growth of the first mode(wavenumber k1)relies heavily on the second mode(wavenumber k2)due to the mode coupling ***,for cases where k2 is an even or odd multiple of k1,the growth of the first mode is inhibited or promoted depending on its initial amplitude sign and the phase difference between two basic waves,while for cases where k2 is a non-integer multiple of k1,the second mode has negligible influence on the first *** a systematic study,signs of perturbation amplitudes of the generated k2−k1 and k2+k1 waves are obtained for all possible dual-mode configurations,which are reasonably predicted by a modified Haan model(Phys Fluids B 3:2349-2355,1991).

关键词： Converging Richtmyer-Meshkov instability Dual-mode interface Mode coupling

Molecular dynamics simulation of cylindrical Richtmyer-Meshkov instability

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Science China(Physics,Mechanics & Astronomy) 2018年第11期61卷 61-71页

作者： Zhenhong Wu Shenghong Huang Juchun Ding Weirong Wang xisheng luo Department of Modern Mechanics University of Science and Technology of China

The microscopic-scale Richtmyer-Meshkov(RM) instability of a single-mode Cu-He interface subjected to a cylindrically converging shock is studied through the classical molecular dynamics simulation. An unperturbed interface is first considered to examine the flow features in the convergent geometry, and notable distortions at the circular inhomogeneity are observed due to the atomic fluctuation. Detailed processes of the shock propagation and interface deformation for the single-mode interface impacted by a converging shock are clearly captured. Different from the macroscopic-scale situation, the intense molecular thermal motions in the present microscale flow introduce massive small wavelength perturbations at the single-mode interface, which later significantly impede the formation of the roll-up structure. Influences of the initial conditions including the initial amplitude,wave number and density ratio on the instability growth are carefully analyzed. It is found that the late-stage instability development for interfaces with a large perturbation does not depend on its initial amplitude any more. Surprisingly, as the wave number increases from 8 to 12, the growth rate after the reshock drops gradually. The distinct behaviors induced by the amplitude and wave number increments indicate that the present microscopic RM instability cannot be simply characterized by the amplitude over wavelength ratio(η). The pressure history at the convergence center shows that the first pressure peak caused by the shock focusing is insensitive to η, while the second one depends heavily on it.

关键词： molecular dynamics simulation Richtmyer-Meshkov instability converging shock

Numerical study on the evolution of the shock-accelerated SF_6 interface:Influence of the interface shape

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Science China(Physics,Mechanics & Astronomy) 2012年第2期55卷 284-296页

作者： FAN MeiRu ZHAI ZhiGang SI Ting luo xisheng ZOU LiYong TAN DuoWang Department of Modern Mechanics University of Science and Technology of ChinaHefei 230026China National Key Laboratory of Shock Wave and Detonation Physics Institute of Fluid Physics Chinese Academy of Engineering PhysicsMianyang 621900China

The early phases of the shock interaction process on two-dimensional interfaces with different shapes are numerically investigated in this study,which are closely related to the shock refraction and reflection,vorticity production and *** numerical method employs an adaptive unstructured quadrilateral mesh,which can capture the wave pattern and interface evolution very *** are carried out under the conditions of an incident shock Mach number of 1.2 and the light/heavy (air/SF 6) *** different shapes are considered in the simulations:rectangle,ellipse,diamond and two kinds of *** results show that the interfacial shapes can influence the wave patterns particularly on the shape and evolution of refracted shock *** generation and the distribution of vorticity on the interfaces with five different shapes also have *** circulation deposition on five interfaces is quantitatively investigated and compared with theoretical model.A good agreement is found between the numerical results and the predictions by the theoretical *** characteristic scales of the interface are *** the influence of nonlinear-acoustic effect and vorticity effect,the interfaces present different evolution modes.

关键词： binaries: interfacial instability planar shock different shapes

Interaction of a planar shock wave with two heavy/light interfaces

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Acta Mechanica Sinica 2022年第9期38卷 23-35页

作者： Yibo Zhang Zhangbo Zhou Juchun Ding xisheng luo Advanced Propulsion Laboratory Department of Modern MechanicsUniversity of Science and Technology of ChinaHefei230026China

The interaction of a planar shock with SF_(6)/Ar/He dual interfaces(SF_(6)/Ar interface is sinusoidal and Ar/He interface is unperturbed)is numerically studied with a compressible multi-component flow solver that is capable of simultaneously capturing discontinuities and resolving small-scale smooth *** cases with different interface distances and incident shock strengths are *** all cases,after the shock impact,the amplitude of the first interface reduces gradually to zero(i.e.,phase inversion)and then increases continuously in the negative *** rarefaction wave(RW2)reflected from the second interface promotes or suppresses the development of the first interface depending on the interface distance(D).Specifically,if D is small,RW2 arrives at the first interface at a time before phase inversion,and thus promotes the instability growth at the first *** D is large,RW2 encounters the first interface at a time after phase inversion,and thus suppresses the instability growth.A theoretical model for the critical distance,under which the first interface just completes phase inversion at the arrival time of RW2,is *** this model,one can regulate the instability growth at the first interface by giving a desired *** development of the second interface belongs to non-standard Richtmyer-Meshkov instability,which depends heavily on the phase of the rippled transmitted *** is found that the model of Ishizaki(***.E 53,R5592,1996)fails to predict the perturbation growth of the second interface for cases where the transmitted shock is at phase 2 due to the ignorance of baroclinic vorticity.A new model considering the combined effects of baroclinic vorticity,velocity perturbation,and pressure disturbance is proposed,which gives a reasonable prediction of perturbation growth at the second interface.

关键词： Richtmyer-Meshkov instability Dual interfaces Rarefaction wave Rippled shock

On transition of type V interaction in double-wedge flow with non-equilibrium effects

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Theoretical & Applied Mechanics Letters 2016年第6期6卷 282-285页

作者： Wentao Xiong Yujian Zhu xisheng luo Advanced Propulsion Laboratory Department of Modern MechanicsUniversity of Science and Technology of China

The transition between regular reflection （RR） and Mach reflection （MR） of type V shock-shock interaction on a double-wedge geometry with high temperature non-equilibrium effects is investigated by extended shock-polar method and numerical simulation. First, the critical angles of transition from detachment criterion and yon Neumann criterion are determined by the extended shock-polar method considering the non-equilibrium effects. Then wave patterns and the transition process are numerically obtained. Results of the critical transition angles from shock-polar calculation and numerical simulation show evident disagreement, indicating transition mechanism between RR and MR of type V interaction is changed. By comparing with the frozen counterpart, it is also found that non-equilibrium effects lead to a larger critical wedge angle and a larger hysteresis interval.

关键词： Shock interaction Non-equilibrium effects Shock polar Hypersonic flow