TY - JOUR
T1 - Rarefaction-driven Rayleigh-Taylor instability. Part 1. Diffuse-interface linear stability measurements and theory
AU - Morgan, R. V.
AU - Likhachev, O. A.
AU - Jacobs, J. W.
N1 - Publisher Copyright:
© 2016 Cambridge University Press.
PY - 2016/2/15
Y1 - 2016/2/15
N2 - Theory and experiments are reported that explore the behaviour of the Rayleigh-Taylor instability initiated with a diffuse interface. Experiments are performed in which an interface between two gases of differing density is made unstable by acceleration generated by a rarefaction wave. Well-controlled, diffuse, two-dimensional and three-dimensional, single-mode perturbations are generated by oscillating the gases either side to side, or vertically for the three-dimensional perturbations. The puncturing of a diaphragm separating a vacuum tank beneath the test section generates a rarefaction wave that travels upwards and accelerates the interface downwards. This rarefaction wave generates a large, but non-constant, acceleration of the order of , where is the acceleration due to gravity. Initial interface thicknesses are measured using a Rayleigh scattering diagnostic and the instability is visualized using planar laser-induced Mie scattering. Growth rates agree well with theoretical values, and with the inviscid, dynamic diffusion model of Duff et al. (Phys. Fluids, vol. 5, 1962, pp. 417-425) when diffusion thickness is accounted for, and the acceleration is weighted using inviscid Rayleigh-Taylor theory. The linear stability formulation of Chandrasekhar (Proc. Camb. Phil. Soc., vol. 51, 1955, pp. 162-178) is solved numerically with an error function diffusion profile using the Riccati method. This technique exhibits good agreement with the dynamic diffusion model of Duff et al. for small wavenumbers, but produces larger growth rates for large-wavenumber perturbations. Asymptotic analysis shows a decay in growth rates as for large-wavenumber perturbations.
AB - Theory and experiments are reported that explore the behaviour of the Rayleigh-Taylor instability initiated with a diffuse interface. Experiments are performed in which an interface between two gases of differing density is made unstable by acceleration generated by a rarefaction wave. Well-controlled, diffuse, two-dimensional and three-dimensional, single-mode perturbations are generated by oscillating the gases either side to side, or vertically for the three-dimensional perturbations. The puncturing of a diaphragm separating a vacuum tank beneath the test section generates a rarefaction wave that travels upwards and accelerates the interface downwards. This rarefaction wave generates a large, but non-constant, acceleration of the order of , where is the acceleration due to gravity. Initial interface thicknesses are measured using a Rayleigh scattering diagnostic and the instability is visualized using planar laser-induced Mie scattering. Growth rates agree well with theoretical values, and with the inviscid, dynamic diffusion model of Duff et al. (Phys. Fluids, vol. 5, 1962, pp. 417-425) when diffusion thickness is accounted for, and the acceleration is weighted using inviscid Rayleigh-Taylor theory. The linear stability formulation of Chandrasekhar (Proc. Camb. Phil. Soc., vol. 51, 1955, pp. 162-178) is solved numerically with an error function diffusion profile using the Riccati method. This technique exhibits good agreement with the dynamic diffusion model of Duff et al. for small wavenumbers, but produces larger growth rates for large-wavenumber perturbations. Asymptotic analysis shows a decay in growth rates as for large-wavenumber perturbations.
KW - buoyancy-driven instability
KW - gas dynamics
KW - turbulent mixing
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U2 - 10.1017/jfm.2016.46
DO - 10.1017/jfm.2016.46
M3 - Article
AN - SCOPUS:84958260506
SN - 0022-1120
VL - 791
SP - 34
EP - 60
JO - Journal of Fluid Mechanics
JF - Journal of Fluid Mechanics
ER -