Direct numerical simulation of double-diffusive convection at vibrations

The problem of the evolution of double-diffusive convection in a plane layer under the action of external vibrations is solved numerically. A two-layered system of miscible fluids placed in the vertical fields of gravity and linear translational vibrations is considered. The former is the generator of convection: due to the difference in the diffusivity of the species dissolved, unstably stratified fluid regions are formed in the layer. Water is used as a continuous medium. The bottom layer is the solution of sodium chloride and it has a higher density than the top layer formed by the glucose solution. Initially, the system is stably stratified. The problem is solved in a two-dimensional transitional formulation by means of the ANSYS Fluent commercial software. The change in the behavior of fluids under the action of vibrations is studied. Convective structures and density profiles at different vibrational acceleration magnitudes, as well as the evolution of convective characteristics, are considered. Analysis of the system behavior is conducted in two aspects: global and local. Global analysis implicates the description of the processes taking place in the scale of the entire layer, and local analysis focuses on the dynamics of separate convective structures. The main vibration effect results in the convection slowdown. In the global scale, this manifests itself as a decrease in the growth rate of the convective structures; the magnitude of this effect increases (is stored) with time. In the local scale, under relatively low vibrational accelerations, the convection onset is delayed, whereas at high accelerations the growth of convective structures is reoriented along the horizontal direction. The results obtained can be used to develop vibratory control methods for diffusive-reactive systems.