TY - JOUR

T1 - Rarefaction-driven Rayleigh-Taylor instability. Part 2. Experiments and simulations in the nonlinear regime

AU - Morgan, R. V.

AU - Cabot, W. H.

AU - Greenough, J. A.

AU - Jacobs, J. W.

N1 - Publisher Copyright:
© 2018 Cambridge University Press.

PY - 2018/3/10

Y1 - 2018/3/10

N2 - Experiments and large eddy simulation (LES) were performed to study the development of the Rayleigh-Taylor instability into the saturated, nonlinear regime, produced between two gases accelerated by a rarefaction wave. Single-mode two-dimensional, and single-mode three-dimensional initial perturbations were introduced on the diffuse interface between the two gases prior to acceleration. The rarefaction wave imparts a non-constant acceleration, and a time decreasing Atwood number, A=(p2-p1)/(p2+p1)p2 and p1 where are the densities of the heavy and light gas, respectively. Experiments and simulations are presented for initial Atwood numbers of A = 0:49, A = 0:63, A = 0:82 and A = 0:94. Nominally two-dimensional (2-D) experiments (initiated with nearly 2-D perturbations) and 2-D simulations are observed to approach an intermediate-time velocity plateau that is in disagreement with the late-time velocity obtained from the incompressible model of Goncharov (Phys. Rev. Lett., vol. 88, 2002, 134502). Reacceleration from an intermediate velocity is observed for 2-D bubbles in large wavenumber, k=2/=0:247 mm-1, experiments and simulations, where is the wavelength of the initial perturbation. At moderate Atwood numbers, the bubble and spike velocities approach larger values than those predicted by Goncharov's model. These late-time velocity trends are predicted well by numerical simulations using the LLNL Miranda code, and by the 2009 model of Mikaelian (Phys. Fluids., vol. 21, 2009, 024103) that extends Layzer type models to variable acceleration and density. Large Atwood number experiments show a delayed roll up, and exhibit a free-fall like behaviour. Finally, experiments initiated with three-dimensional perturbations tend to agree better with models and a simulation using the LLNL Ares code initiated with an axisymmetric rather than Cartesian symmetry.

AB - Experiments and large eddy simulation (LES) were performed to study the development of the Rayleigh-Taylor instability into the saturated, nonlinear regime, produced between two gases accelerated by a rarefaction wave. Single-mode two-dimensional, and single-mode three-dimensional initial perturbations were introduced on the diffuse interface between the two gases prior to acceleration. The rarefaction wave imparts a non-constant acceleration, and a time decreasing Atwood number, A=(p2-p1)/(p2+p1)p2 and p1 where are the densities of the heavy and light gas, respectively. Experiments and simulations are presented for initial Atwood numbers of A = 0:49, A = 0:63, A = 0:82 and A = 0:94. Nominally two-dimensional (2-D) experiments (initiated with nearly 2-D perturbations) and 2-D simulations are observed to approach an intermediate-time velocity plateau that is in disagreement with the late-time velocity obtained from the incompressible model of Goncharov (Phys. Rev. Lett., vol. 88, 2002, 134502). Reacceleration from an intermediate velocity is observed for 2-D bubbles in large wavenumber, k=2/=0:247 mm-1, experiments and simulations, where is the wavelength of the initial perturbation. At moderate Atwood numbers, the bubble and spike velocities approach larger values than those predicted by Goncharov's model. These late-time velocity trends are predicted well by numerical simulations using the LLNL Miranda code, and by the 2009 model of Mikaelian (Phys. Fluids., vol. 21, 2009, 024103) that extends Layzer type models to variable acceleration and density. Large Atwood number experiments show a delayed roll up, and exhibit a free-fall like behaviour. Finally, experiments initiated with three-dimensional perturbations tend to agree better with models and a simulation using the LLNL Ares code initiated with an axisymmetric rather than Cartesian symmetry.

KW - gas dynamics

KW - nonlinear instability

KW - turbulent mixing

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U2 - 10.1017/jfm.2017.893

DO - 10.1017/jfm.2017.893

M3 - Article

AN - SCOPUS:85040732972

VL - 838

SP - 320

EP - 355

JO - Journal of Fluid Mechanics

JF - Journal of Fluid Mechanics

SN - 0022-1120

ER -