In this paper we report on 2D numerical simulations concerning linear and nonlinear evolution of surface-tension-driven instability in two-fluid systems heated from below using classical and phase-field models. In the phase-field formalism, one introduces an order parameter called phase-field function to characterize thermodynamically the phases. All the system parameters are assumed to vary continuously from one fluid bulk to another (as linear functions of the phase-field). The Navier-Stokes equation (with some extra terms) and the heat equation are written only once for the whole system. The evolution of the phase-field is described by the Cahn-Hilliard equation. In the sharp-interface limit the results found by the phase-field formalism recover the results given by the classical formulation.
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