Effect of Initial Conditions on the Development of Rayleigh–Taylor Instability

Abstract

We present the results of a large number of 2D and 3D simulations of the Rayleigh–Taylor instability development. The simulations were made with the help of the EGAK code developed at RFNC–VNIIEF and performed using fine grids (for 2D, 1000 × 2000; for 3D, 10003) for two ideal fluids of different densities in the gravitational field with different initial perturbations at the interface. We present an analysis of the results of 2D and 3D simulations compared with the evolutionary model of a turbulent mixing layer. This theoretical approach is based on the idea of a “perturbation age” where the age of a perturbation is the product of its height and the wave number. The “critical age” represents the boundary between the linear and nonlinear stages of the instability development (a boundary that is different for 2D and 3D problems). Central in this model is information on the initial perturbation spectra and their role in the appearance of low wave-number modes at a later stage of the turbulent mixing layer evolution. The instability evolution model enables an adequate interpretation of various peculiarities in the development of a turbulent layer.