The Numerical Simulation Research Of Roughness Elements Impact On Boundary Layer

Because the boundary layer flow plays an important role in our daily life and industrial applications, this paper uses the tool of Direct Numerical Simulation to research the phenomena of air flows through the roughness of boundary layer. The results are compared with the experimental data to explore the law of evolution and development under different flow conditions.Firstly, systematic reviews are done to the background knowledge and the history of boundary layer studies, the research of roughness elements in the boundary layer flow, development of direct numerical simulation. Then our study of hemispherical roughness element is purposed, which are significant of the boundary layer study.After that, the numerical simulation model and calculation methods of this work are described. The mathematical equation of spatial evolution and time advance, the immersed boundary method that are used to calculate the force between the fluid and the roughness element, and the set of entrance and exit boundary conditions are briefly introduced. To verify the current procedures and to prove the feasibility of Direct Numerical Simulation, the classic case of cavity flow is simulated with contrast of the ancestors’experiments.Finally, simulations are done to the two hemispheres of roughness elements under high Reynolds number turbulent boundary layer. The intuitive description of the view are given, and data such as the velocity field, pressure field, Reynolds stress are analyzed in-depth in the area of roughness, and the law of flow field evolution beyond roughness elements are explored. The foundations for research of adding roughness elements, complex of multiphase flow, heat transfer boundary layer phenomenon are successfully build.