Lattice Boltzmann Method And Simulation Of Oscillatory Laminar Boundary Layer Flow

Lattice Boltzmann (LB) method is a novel numerical simulation method arising inComputational Fluid Dynamics (CFD) in recent years. Different from conventionalnumerical method in CFD (such as finite difference method, finite element method andet al.), the basic theories of LB method are molecular kinetic theory and statisticmechanics. From 1988, when it was first brought forward, LB method makes progressrapidly, and exhibits unique predominance and potential with successful applications inmany scientific fields. The LB method is used to solve the coastal engineering problemsin the present thesis.First, the developing process, theoretical background and basic idea of LatticeBoltzmann method are introduced, and the principal governing equations are derived.Then, the LB method is applied in the oscillatory laminar boundary layer problem. Theincompressible D 2Q 9 model of LB method is employed to simulate the oscillatorylaminar boundary layer flows under linear and cnoidal wave motion respectively. Theoscillatory laminar boundary layer problem is first transformed into the oscillatory flatflow problem by the coordinate conversion method for the mathematical simplicity, andthen is reverted to the required problem. When simulating the oscillatory flat flow, aperiodically variable force is added on the bottom boundary as the driving force tosatisfy the velocity condition, which is different from the traditional bounce-backboundary scheme in LB method. In the end, a good comparison is found between thenumerical simulation results and the theoretical solutions, suggesting that LB methodcan be successfully applied in the research of coastal engineering.This thesis not only puts forward a completely fresh numerical simulation methodfor the study of oscillatory boundary layer problem, but also presents an innovation andprogress for Lattice Boltzmann method itself.