Lattice Boltzmann model with double distribution function is used to study fast phase-change heat transfer in single-pulse laser metal drilling process. Flow and heat transfer of the melted metal material is considered and an immersion moving boundary scheme was used to track solid-liquid interface in the process. Pure heat conduction model and heat transfer model considering convection are used to simulate the process and the results are compared with experimental data. It shows that flow of the melted material has a great impact on phase change heat transfer during laser drilling and results with model that considers flow heat transfer are closer to experimental data. Melting rate, melting depth and temperature field distribution were analyzed, and effects of laser parameters on phase transition process were discussed. It shows that at the end of a pulse, the larger the pulse width of laser, the smaller hole depth, the larger aperture, and the lower temperature of shorter pulse laser are found.

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.

Phase change heat transfer of a gold particle irradiated by ulter-fast laser was studied. Position of solid-liquid interface was determined with coupling interface energy balance equation and interface tracking method for nucleation dynamics. In addition, effects of laser parameters on sintering process were studied. It showed that as laser irradiates gold particle vertically, melting phenomenon occurs mainly in poles of particle. Bottom of particle melts earlier than top and melting volume is smaller. As laser pulse width becomes shorter melting is earlier and melting volume increases. Melting degree of particle increases with laser heat source fluence.

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.

A parallel finite element solver is developed for simulation of the unsteady incompressible viscous flows. Implicit mid-point scheme is used to discretize time variable. Based on unstructured grid, velocity and pressure are discretized by classical P2-P1 Taylor-Hood mixed finite element. Resulting linear algebraic systems are large-scale, sparse, non-symmetric and ill-conditioned. Using a specially designed iterative strategy, it is solved by preconditioned GMRES method with modified pressure-convection-diffusion(PCD) preconditioner. A number of numerical experiments verify scability and validity of the solver. Especially, driven cavity flow simulation in 3D (Re=3200.0) clearly shows existence of primary eddy, downstream secondary eddy, upstream secondary eddy, end-wall vortices and T-G-like vortices. A parallel efficiency comparison with least-squares commutator(LSC) preconditioner is also given.