The dynamics of Rayleigh-Taylor turbulence convection in presence of an alternating, time periodic acceleration is studied by means of extensive direct numerical simulations of the Boussinesq equations. Within this framework, we discover a new mechanism of relaminarization of turbulence: The alternating acceleration, which initially produces a growing turbulent mixing layer, at longer times suppresses turbulent fluctuation and drives the system toward an asymptotic stationary configuration. Dimensional arguments and linear stability theory are used to predicts the width of the mixing layer in the asymptotic state as a function of the period of the acceleration. Our results provide an example of simple control and suppression of turbulent convection with potential applications in different fields.

The Korteweg-de Vries equation that describes surface gravity water wave dynamics in shallow water is well known to admit cnoidal wave solutions, i.e. periodic travelling waves with stationary wave shape. Such type of periodic wave patterns can be also found in the deep-water waves with the envelopes that follow the dynamics of the nonlinear Schrödinger equation (NLS). A particular class of NLS periodic and stationary solutions are cnoidal (CN) and dnoidal (DN) envelopes. This one parameter family of solutions has as limiting cases either the envelope soliton or a constant background. In this experimental study, we discuss the physical features of such waves and emphasize the particular effect of dissipation, as observed in several hydrodynamic experiments that have been conducted in several water wave facilities with different dimensions. Experiments on such type of periodic wave envelopes in a large facility have been already reported in the early 1990s. These studies demonstrated significant deviation of the DN-type envelopes from theory. Here, we show that these deviations are due to the effect of dissipation that can be qualitatively considered by adapting the NLS framework accordingly. Reducing the amplitude of the carrier wave makes the wave field susceptible to dissipation effects. Our experiments prove that the dissipation is indeed responsible for phase-shift pulsations for DN-type envelopes.

No abstract