Numerical Simulation Of Boundarv Laver Transition Based On Reynolds Averaged Navier-Stokes Method

The boundary layer transition has a significant influence on the aircraft surface frictional resistance coefficient and aerodynamic heat flux.And it's an important research direction in the field of fluid mechanics.The study of the boundary layer transition problem not only helps to reveal the complex formation mechanism of turbulence,but also has important engineering guidance significance.Based on the RANS(Reynolds Averaged Navier-Stokes)methods for computational fluid dynamics,the ?-Re?t transition model is expanded and the numerical calculations of boundary layer transitional flow which is under the influence of multiple factors such as wall roughness,pressure gradient,cross-flow instability,and flow Reynolds number are carried out in this thesis.To solve the complex flow phenomenon accurately,this paper develops a set of parallelized CFD calculation program based on the finite volume method.Furthermore,LU-SGS implicit time propulsion method and local time steps are used to accelerate the convergence speed of the discrete equations.In order to solve the problem of boundary layer transition,the k-? SST turbulent model and the ?-Re?t transition model are introduced.Through several simulations of flat/airplane transitional flow cases,the reliability of the present solver is confirmed,which ensure this solver can be used for the complex transition simulation in the next step.There are many factors affecting the boundary transition.In order to expand the application scope of the ?-Re?t transition model and simulate cross-flow instability transitional flow,rough surface induced transitional flow and hypersonic compressible transitional flow accurately,this paper has carried out different corrections for the ?-Re?t transition model respectively.For cross-flow instability transitional flow,the cross-flow correction is realized by programing based on the localized strength characteristic parameter.And some examples are studied to verify the accuracy of the model.For rough surface induced transitional flow,the turbulent model's rough wall surface boundary conditions are added,and the equivalent sand model is introduced to represent the roughness of the wall surface.Thus,the rough surface induced transitional model is realized by programing.For hypersonic compressible transitional flow,the Reynolds number of the momentum thickness and the turbulent model is modified to realize the model's ability of simulating the hypersonic boundary-layer transitional flow.Finally,numerical simulations are carried out to verify the expanded model's ability of simulating the cross-flow instability transitional flow,rough surface induced transitional flow and hypersonic compressible transitional flow,with boundary layer transition examples such as swept wing,rough flat,compressible corner,and hypersonic blunt cone.And the paper gives deep research on the influence of Reynolds number,sweep angle and surface roughness on the boundary layer transition.