A comparative study of the turbulent RayleighTaylor instability using highresolution threedimensional numerical simulations: The AlphaGroup collaboration
Abstract
The turbulent RayleighTaylor instability is investigated in the limit of strong modecoupling using a variety of highresolution, multimode, three dimensional numerical simulations (NS). The perturbations are initialized with only short wavelength modes so that the selfsimilar evolution (i.e., bubble diameter D_{b}∝amplitude h_{b}) occurs solely by the nonlinear coupling (merger) of saturated modes. After an initial transient, it is found that h_{b}̃α_{b}Agt^{2},_{ where A=Atwood number, g=acceleration, and t=time. The NS yield Db̃hb}/3 in agreement with experiment but the simulation value α_{b}̃0.025±0.003 is smaller than the experimental value α_{b}̃0.057±0.008. By analyzing the dominant bubbles, it is found that the small value of α_{b} can be attributed to a density dilution due to finescale mixing in our NS without interface reconstruction (IR) or an equivalent entrainment in our NS with IR. This may be characteristic of the mode coupling limit studied here and the associated α_{b} may represent a lower bound that is insensitive to the initial amplitude. Larger values of α_{b} can be obtained in the presence of additional long wavelength perturbations and this may be more characteristic of experiments. Here, the simulation data are also analyzed in terms of bubble dynamics, energy balance and the density fluctuation spectra.
 Publication:

Physics of Fluids
 Pub Date:
 May 2004
 DOI:
 10.1063/1.1688328
 Bibcode:
 2004PhFl...16.1668D
 Keywords:

 47.55.Dz;
 47.20.Ma;
 47.27.Qb;
 47.27.Eq;
 47.10.+g;
 Interfacial instabilities