Interface Width Effect on the Weakly Nonlinear Rayleigh-Taylor Instability in Spherical Geometry

Interface width effect on the spherical Rayleigh-Taylor instability in the weakly nonlinear regime is studied by numerical simulations. For Legendre perturbation mode P-n with wave number k(n) and interface half-width L, the commonly adopted empirical linear growth rate formula gamma(em)(n)(L)=gamma(n)/root 1+k(n)L is found to be sufficient in spherical geometry. At the weakly nonlinear stage, the interface width affects the mode coupling processes. The development of the mode P-2n is substantially influenced by the interface width. Moreover, the nonlinear saturation amplitude increases with the interface width.