Rarefaction-driven Rayleigh–Taylor instability. Part 1. Diffuse-interface linear stability measurements and theory

Journal Article · Mon Feb 15 00:00:00 EST 2016 · Journal of Fluid Mechanics

DOI:https://doi.org/10.1017/jfm.2016.46· OSTI ID:1436482

Morgan, R. V. ^[1]; Likhachev, O. A. ^[1]; Jacobs, J. W. ^[1]

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1. Univ. of Arizona, Tucson, AZ (United States). Dept. of Chemistry and Biochemistry

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$$1000g_{0}$$, where$$g_{0}$$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 Duffet 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 Duffet al. for small wavenumbers, but produces larger growth rates for large-wavenumber perturbations. Asymptotic analysis shows a$$1/k^{2}$$decay in growth rates as$$k\rightarrow \infty$$for large-wavenumber perturbations.

• Research Organization: Univ. of Arizona, Tucson, AZ (United States). Dept. of Chemistry and Biochemistry
• Sponsoring Organization: USDOE National Nuclear Security Administration (NNSA)
• Grant/Contract Number: NA0002000
• OSTI ID: 1436482
• Journal Information: Journal of Fluid Mechanics, Vol. 791; ISSN 0022-1120
• Publisher: Cambridge University Press
• Country of Publication: United States
• Language: English

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