Natural convection problem in a deformable outlet cavity is studied with lattice Boltzmann method. Heated size at left wall are set to two conditions: The whole wall (H) and the middle wall (0.5H). The right wall is open to external environment. The upper and lower boundaries are adiabatic and their right end can be moved up and down to adjust size of the right outlet. Effects of Rayleigh number (10⁴ ≤ Ra ≤ 10⁶), the right exit size (1.0H ≤ L ≤ 2.0H), the left wall heating size (L_h=0.5H or L_h=H) on streamlines, isothermal lines, local Nusselt numbers and average Nusselt numbers are investigated. It shows that heat transfer in the cavity increases with the increase of Rayleigh number, which manifests as size of elliptical quasi-stationary region in the cavity increases and is closer to the upper and lower adiabatic boundaries. Thickness of thermal stratification is gradually reduced and average Nusselt number is increased. However, increase of the right outlet has a different degree of influence on heat transfer effect in the cavity. As the heating size is in the middle of the left wall surface, size of the right side opening does not significantly affect the heat exchange. In addition, at the left wall heating size of 0.5H it shows a higher average heat transfer efficiency. An empirical prediction of functional relation between average Nusselt number and control parameters is proposed. The fitting function satisfies practice and design in projects.

An accurate equation of state (EOS) for carbon dioxide is coupled into an improved lattice Boltzmann equation (LBE) model. With the model continuous interfacial dynamics of carbon dioxide in two phase in a microchannel, including breaking up, coalescence, deformation, and mass exchange between gas and liquid phases, is studied. It is found that flows achieve a steady-state as balance of breaking up and coalescence is reached, and mass exchange occurs. Comprehensive results show that flow shape at steady-state depends mainly on surface tension, inertial force, wettability of channel surface, and initial volume fraction. Specially, formative bubbles or droplets are almost spherical as inertial force is smaller than surface tension. As surface tension overcomes inertial force, slug flow is formed since bubbles or droplets are easy to expand to contact with solid surface. On the other hand, it shows that influence of wettability on flow pattern is also important. Slug flow is observed if contact angle is small while annular flow is observed if contact angel is large. At different volume fraction slug flow and annular flow are obtained.

We adopted lattice Boltzmann method to simulate double diffusion mixed convection, fluid-solid conjugate heat transfer and adsorption process in a lid-driven composite enclosure filled with homogeneous medium at pore scale. Influences of buoyancy ratio Br (-100 ≤ Br ≤ 100) and adsorption rate constant k₁ (0.001 ≤ k₁ ≤ 0.005) on characteristics of heat and mass transfer were compared at porosity ε=0.79, Prandtl number Pr=0.7, Grashof number Gr=10⁴ and Lewis number Le=1.0. Streamlines, isotherms, isoconcentrations, adsorption capacity (C_S), average Nusselt number Nu_av and Sherwood number Sh_av of the left heated wall under different parameters were discussed in detail. It shows that Br affects adsorption by changing concentration distribution around medium in flow field; Increasing k₁ improves significantly adsorption efficiency and adsorption capacity.

We adopt lattice Boltzmann method to investigate double diffusive natural convection around a heated cylinder in an enclosure with Soret and Dufour effects. The inner heated cylinder is located at center of a square enclosure and four surrounding walls are assumed with low temperature and concentration. In the model, distributions of velocity, temperature and concentration are solved with three independent LBGK equations which are combined into a coupled equation through Boussinesq approximation. Influences of Soret number and Dufour number on double diffusive natural convection are analyzed. Streamlines, isotherms, isoconcentrations, average Nusselt and Sherwood numbers around heated cylinder in enclosure are presented. It shows that Soret and Dufour effects have significant influence on double diffusive natural convection.