On the stability of cosmic ray dominated shocks
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We report that a secondary, Rayleigh‐Taylor type instability can exist in cosmic‐ray dominated media which are perturbed by the 1D acoustic instability. Using the local WKB approximation, the growth rate of the secondary instability is shown to be comparable to that of the 1D acoustic instability itself in the cases we have considered. We show that flows in the precursor and postshock regions can become highly turbulent due to the secondary instability. As in the 1D acoustic instability, however, the cosmic‐ray pressure is not significantly affected by the presence of the secondary instability, because the cosmic ray diffusion timescale from the perturbations is much smaller than the growth timescale of the instability.Keywords:
WKB approximation
Streaming instability
Rayleigh–Taylor instability
Richtmyer–Meshkov instability
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A numerical simulation of two-dimensional compressible Navier-Stokes equations using a high-order weighted essentially nonoscillatory finite difference shock capturing scheme is carried out in this paper, to study the effect of shock waves on the development of Rayleigh-Taylor instability. Shocks with different Mach numbers are introduced ahead or behind the Rayleigh-Taylor interface, and their effect on the transition to instability is demonstrated and compared. It is observed that shock waves can speed up the transition to instability for the Rayleigh-Taylor interface significantly. Stronger shocks are more effective in this speed-up process.
Rayleigh–Taylor instability
Richtmyer–Meshkov instability
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Rayleigh–Taylor (RT) instability is studied in this article in an inhomogeneous complex plasma. It has been observed that RT instability may occur when the mass density of the dust particles exhibits inhomogeneity in certain regions. The growth rate of the RT instability increases as the perturbed wavelength decreases and also as the gravitational acceleration increases. Moreover, it is also found that the charged characteristics of dust fluids play an important role in suppressing the RT instability in complex plasmas. Our results have potential applications in complex plasmas.
Rayleigh–Taylor instability
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Richtmyer–Meshkov instability
Rayleigh–Taylor instability
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Richtmyer–Meshkov instability
Rayleigh–Taylor instability
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The validity of gradient-diffusion closures for modeling turbulent transport in multi-mode Rayleigh-Taylor and reshocked Richtmyer-Meshkov instability-induced mixing is investigated using data from three-dimensional spectral/tenth-order compact difference and ninth-order weighted essentially non-oscillatory simulations, respectively. Details on the numerical methods, initial and boundary conditions, and validation of the results are discussed elsewhere [2, 3]. First, mean and fluctuating fields are constructed using spatial averaging in the two periodic flow directions. Then, quantities entering eddy viscosity-type gradient-diffusion closures, such as the turbulent kinetic energy and its dissipation rate (or turbulent frequency), and the turbulent viscosity are constructed. The magnitudes of the terms in the turbulent kinetic energy transport equation are examined to identify the dominant processes. It is shown that the buoyancy (or shock) production term is the dominant term in the transport equation, and that the shear production term is relatively small for both the Rayleigh-Taylor and Richtmyer-Meshkov cases. Finally, a priori tests of gradient-diffusion closures of the unclosed terms in the turbulent kinetic energy transport equation are performed by comparing the terms constructed directly using the data to the modeled term. A simple method for estimating the turbulent Schmidt numbers appearing in the closures is proposed. Using these turbulent Schmidt numbers,more » it is shown that both the shape and magnitude of the profiles of the dominant terms in the turbulent kinetic energy transport equation across the mixing layer are generally well captured.« less
Richtmyer–Meshkov instability
Rayleigh–Taylor instability
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We study the highly nonlinear stages of the Rayleigh–Taylor instability (RTI) for three-dimensional flow. The proposed numerical and analytical methods are original approaches to the problem. They validate each other and the obtained results agree well.
Rayleigh–Taylor instability
Richtmyer–Meshkov instability
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Richtmyer–Meshkov instability
Rayleigh–Taylor instability
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Richtmyer–Meshkov instability
Rayleigh–Taylor instability
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Richtmyer–Meshkov instability
Rayleigh–Taylor instability
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A formalism is presented for calculating all the normal growth modes of the Rayleigh-Taylor instability in a stratified fluid of arbitrary profile. The classical instability is suppressed by the introduction of a finite density gradient at the interface, a technique applicable to inertial-confinement fusion targets.
Rayleigh–Taylor instability
Richtmyer–Meshkov instability
Formalism (music)
Stratified flows
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