Formation of Initial Perturbation of Rayleigh‐Taylor Instability in Supernovae and Laser‐irradiated Targets—Is There Any Similarity?

2000 ◽  
Vol 127 (2) ◽  
pp. 219-225 ◽  
Author(s):  
H. Azechi ◽  
K. Shigemori ◽  
M. Nakai ◽  
N. Miyanaga ◽  
H. Takabe
Keyword(s):  
Initial Perturbation ◽  
Taylor Instability ◽  
Rayleigh Taylor Instability

scholarly journals The effects of forced small-wavelength, finite-bandwidth initial perturbations and miscibility on the turbulent Rayleigh–Taylor instability

2015 ◽  
Vol 787 ◽  
pp. 50-83 ◽  
Author(s):  
M. S. Roberts ◽  
J. W. Jacobs
Keyword(s):  
High Speed ◽  
Initial Perturbation ◽  
Mixing Layer ◽  
Experimental Studies ◽  
Growth Parameter ◽  
Video Camera ◽  
Taylor Instability ◽  
Layer Width ◽  
High Speed Video Camera ◽  
Rayleigh Taylor Instability

Rayleigh–Taylor instability experiments are performed using both immiscible and miscible incompressible liquid combinations having a relatively large Atwood number of $A\equiv ({\it\rho}_{2}-{\it\rho}_{1})/({\it\rho}_{2}+{\it\rho}_{1})=0.48$. The liquid-filled tank is attached to a test sled that is accelerated downwards along a vertical rail system using a system of weights and pulleys producing approximately $1g$ net acceleration. The tank is backlit and images are digitally recorded using a high-speed video camera. The experiments are either initiated with forced initial perturbations or are left unforced. The forced experiments have an initial perturbation imposed by vertically oscillating the liquid-filled tank to produce Faraday waves at the interface. The unforced experiments rely on random interfacial fluctuations, resulting from background noise, to seed the instability. The main focus of this study is to determine the effects of forced initial perturbations and the effects of miscibility on the growth parameter, ${\it\alpha}$. Measurements of the mixing-layer width, $h$, are acquired, from which ${\it\alpha}$ is determined. It is found that initial perturbations of the form used in this study do not affect measured ${\it\alpha}$ values. However, miscibility is observed to strongly affect ${\it\alpha}$, resulting in a factor of two reduction in its value, a finding not previously observed in past experiments. In addition, all measured ${\it\alpha}$ values are found to be smaller than those obtained in previous experimental studies.

Simulation of the Tilted Rig Experiment

2012 ◽  
Author(s):  
Bertrand Rollin ◽  
Malcolm J. Andrews
Keyword(s):  
Initial Perturbation ◽  
Mixing Layer ◽  
Variable Density ◽  
Taylor Instability ◽  
Two Dimensional ◽  
Two Fluids ◽  
Eddy Simulation ◽  
Type Variable ◽  
Rayleigh Taylor Instability ◽  
Variable Density Turbulence

The tilted rig experiment is a derivative of the rocket rig experiment designed to study mixing of fluids by the Rayleigh-Taylor instability. In the latter experiment, a tank containing two fluids of different densities is accelerated downwards between two parallel guide rods by a rocket motor. Misalignment between density and pressure gradients trigger the instability leading turbulence and mixing of the fluids. In the tilted rig experiment, the rocket rig is inclined by few degrees off the vertical before firing, creating a slanted initial perturbation interface. The purpose of the tilted rig experiment was to help with calibration of mixing models, as it is a unique two-dimensional Rayleigh-Taylor instability flow. We reproduce conditions similar to this experiment using a Monotone Integrated Large Eddy Simulation (MILES) technique, and for the first time look at statistics of turbulence quantities that appears in “RANS-type” variable density turbulence model. Our statistics show that for the most part, the turbulence quantities in this two-dimensional Rayleigh-Taylor instability configuration behave in a similar fashion as in the planar Rayleigh-Taylor instability configuration when looking in a direction perpendicular to the mixing layer centerline.

Spouting and planform selection in the Rayleigh–Taylor instability of miscible viscous fluids

1998 ◽  
Vol 377 ◽  
pp. 27-45 ◽  
Author(s):  
N. M. RIBE
Keyword(s):  
Viscosity Ratio ◽  
Initial Perturbation ◽  
Taylor Instability ◽  
Viscous Layer ◽  
Weakly Nonlinear ◽  
Subexponential Growth ◽  
Weakly Nonlinear Analysis ◽  
Salt Domes ◽  
Initial Evolution ◽  
Rayleigh Taylor Instability

A weakly nonlinear analysis is used to study the initial evolution of the Rayleigh–Taylor instability of two superposed miscible layers of viscous fluid between impermeable and traction-free planes in a field of gravity. Analytical solutions are obtained to second order in the small amplitude of the initial perturbation of the interface, which consists of either rolls or squares or hexagons with a horizontal wavenumber k. The solutions are valid for arbitrary values of k, the viscosity ratio (upper/lower) γ, and the depth ratio r, but are presented assuming that k=kmax(γ, r), where kmax is the most unstable wavenumber predicted by the linear theory. For all planforms, the direction of spouting (superexponential growth of interfacial extrema) is determined by the balance between the tendency of the spouts to penetrate the less viscous layer, and a much stronger tendency to penetrate the thicker layer. When these tendencies are opposed (i.e. when γ>1 with r>1), the spouts change direction at a critical value of r=rc(γ). Hexagons with spouts at their centres are the preferred planform for nearly all values of γ and r, followed closely by squares; the most slowly growing planform is hexagons with spouts at corners. Planform selectivity is strongest when γ[ges ]10 and r[ges ]γ1/3. Application of the results to salt domes in Germany and Iran show that these correspond to points (γ, r) below the critical curve r=rc(γ), indicating that the domes developed from interfacial extrema having subexponential growth rates.

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