Effect of Solutal Properties and Aspect Ratio on Breaking Time of Two-Layered Double-Diffusive Interface

Double-diffusive convection in a solutally stratified fluid of two layers destabilized by lateral heating and cooling was studied experimentally. In the experiments, the breaking time of the interface, i.e., the time when the mixing of the two layers starts, was measured for five aqueous solutions with different solutes (Na₂CO₃, Na₂SO₄, NaCl, NH₄Cl and KCl) and for three closed vessels with different aspect ratios (A=0.55, 1.1 and 2.2). The initial concentration difference between the two layers and the temperature difference between the two vertical walls were also varied extensively. Based on the result of dimension analysis, a non-dimensional equation was proposed for correlating the breaking time of the interface, t_m, with the thermal Rayleigh number, Ra_t, the initial buoyancy ratio, N₀, and the Schmidt number, Sc. The equation was also valid for experimental data reported in the literature.