Lattice Boltzmann Simulation On Motion Of A Single Bubble Rising Along A Superheated Curved Surface

The standard lattice Boltzmann method (LBM) do have advantages in the simulation of the fluid flow and heat transfer problems in the regular domain. But, the flow field of practical problems tend to have irregular boundaries in which the standard LBM cannot describe the boundaries accurately and the computational efficiency is low. Therefore, it is of great significance to propose the thermal and multiphase flow model of LBM based on body-fitted coordinate system.Given the distinct advantages of calculation of fluid flow in the irregular domain by the generalized form of interpolation lattice Boltzmann method (GILBM), a thermal LBM model in a body-fitted coordinate system has been proposed by combining the thermal LBM model on uniform grids with GILBM, then it is validated by numerically simulating flow around a circular cylinder and the natural convection in horizontal annulus. The streamlines, pressure coefficients and Nusselt numbers around the cylindrical surface are all in good agreement with previous results. Besides, when Ra= 5 x 104, the isotherms between the annuluses calculated by present model agree well with the experimental results by T. H. Kuehn et al.. so do the local equivalent heat conductivities on both inner and outer surfaces of the annulus with average error less than 3%. The above comparison proves the applicability of the proposed model in the simulation of complex flow with large curvature boundaries.Based on the hybrid phase change LBM model in Cartesian coordinate system and the GILBM scheme, a hybrid phase change LBM model in body-fitted coordinate system has also been proposed since the successful application of GILBM in the non-isothermal single-phase fluid system. The model is validated by the bubble growth in superheated liquid and on the horizontal superheated wall whose results are in good agreement with Mikic’s analytical solution and Mukherjee’s experimental result, respectively. Then, the motion characteristic of a single bubble rising along a superheated curved surface under different Jacob numbers has been investigated by proposed model. The results show that during bubble’s rising process, it slides over the curved surface at the beginning, and then it departs from the surface. The bubble growth rate and rising velocity increase with Jacob number, and the curved surface leads to the significant deformation with both horizontal and vertical velocities fluctuating. The fluctuating frequency and amplitude are proportional to Jacob number. After departing from the surface, the bubble becomes small due to the condensation of surrounding supercooled liquid. The disturbance of temperature field caused by bubble strengthens with Jacob number, and the drastic changes of temperature field, in turn, affect the growth of bubble.