Study Of Numerical Simulation Of Natural Convection In A Closed Square Cavity Based On The Lattice Boltzmann Method

The phenomena of natural convection flow and heat transfer in a closed cavity has extensive applicative background in engineering, so it is noticed more and more widely. Large Scale Computation (LSC) has been becoming more and more important in scientific studies and engineering applications with the development of science and technology, and is well recognized as a significant method in addition to the experimental and theoretical approaches. Fluid flows simulation is one of the most important and challenging branches of LSC. A lot of here and overseas scholars do much work in experiment study and numerical simulation.In this thesis, a novel method for computational fluid dynamics--LBM has been used to simulate natural convection in a square cavity, the contents include two parts: one is, the simulation of Rayleigh-Bénard convection. Base on the results of simulation, both the hot bottom-wall is heated uniformly and non-uniformly, their velocity vectors and isotherms are presented, the effects of Rayleigh number are studied, and their samenesses and differences are discussed. When 103≤Ra≤105, the results are in well agreement with the work of Tanmay, and for high Rayleigh number(106≤Ra≤107) which hasn't relevant data of experiment and simulation are reported until now. When observing the simulation results, we can find a new phenomenon: at Ra=107, the fluid flow is in the low turbulence region.And the other one is, the simulation of natural convection. At Ra =103 ~107, their velocity vectors and isotherms are also presented, and the variation of non-dimensional temperature and velocity along the horizontal and vertical centerline of the cavity are showed in this paper.The feasibility,accuracy and numerical stability of the thermal lattice model in the simulation of natural convection are proved by comparing the results with other methods'.From the study of numerical simulation of natural convection heat transfer we can see that: As the Rayleigh number increases, the thickness of the thermal boundary layer reduces obviously, and the temperature gradients augments which is least at the central regime near the top surface. At Ra=107, the natural convection in a square cavity flow is in the low turbulence region. The thermal lattice model puts up well numerical accuracy and stability, when it is in the simulation of high Rayleigh number natural convection.