Lattice Boltzmann Simulation Of Double-diffusive Marangoni Convection In A Double-layer Rectangular Cavity

Crystal materials have been applied extensively in industrial production,especially in the field of microgravity and microelectronics.With the development of space technology,it has been found that the crystal with uniform composition and excellent performance could been produced easily under the microgravity environment where the buoyancy effect could been ignored.However,the quality of crystal materials is affected by the double-diffusive Marangoni convection driven by surface tension in this condition.The numerical simulation of double-diffusive Marangoni convection in a two-layer rectangular cavity controlled by horizontal temperature and concentration gradient is carried out,and the effect of liquid seals on the stability and convection intensity at the interface is investigated by spectrum analysis and phase portrait construction.Then,the transition route of double-diffusive Marangoni convection in a two-layer rectangular cavity is considered,and the influence of the physical properties and geometry of double-layer liquid or liquid seals on stability and heat and mass transfer is solved.The specific conclusions are as follows:Firstly,the effect of liquid seals on the stability and convection intensity at the interface is investigated,and the oscillation mechanism and convection pattern transition of two-layer double-diffusive Marangoni convection is analyzed in detail.The suppressing effect on the interfacial convection by liquid seals could been observed with lowλ（the ratio of interface Reynolds number Re₁ to surface Reynolds number Re₂）,while amplification with largeλ,and the stability increases withλincreases.The transition of double-diffusive Marangoni convection withλ=0.5 is classified as quasi-periodic route,and the variation of flow intensity and heat and mass transfer is non-linear with Re₂.Secondly,the effect of the physical parameters and geometry of two-layer liquid on convection stability and transition are considered.The results show that the convection pattern transits from periodic to quasi-periodic with the increase of Prandtl number Pr and Lewis number Le,and heat and mass transfer increase.The stability increases with Rσ（the ratio of solutal Reynolds number Re_C to thermal Reynolds number Re_T）increases from-1.0 to 1.0,and heat and mass transfer rate increase.The flow stability could been improved under microgravity environment,and flow is unstable with large Grashof number Gr.The periodic pattern could been observed when the liquid seals or the melt is deeper,and instability is serious with the increase of aspect ratio Ar.Finally,the effect of the physical parameters and geometry of liquid seals on interface convection stability and transition are analyzed.The results indicate that the flow pattern transits from quasi-periodic to periodic with the thermal diffusivity ratioα,mass diffusivity ratio D and density ratioρ,and an excellent suppressing effect by liquid seals on interface convection could been found under a suitableα,D andρvalue within periodic model.The flow at the surface is enhanced with kinematic viscos ity ratioνincreases,but at the interface is weakened,so the liquid seals with large viscosity has more obvious suppressing effect.Considered the heat transfer between the free surface and environment,the heat transfer rate and flow intensity at the interface and free surface increase with the Biot number Bi,while the oscillatory frequencies and mass transfer rate decrease.