Abstract: The Galerkin finite element method is applied to calculate the flow field around back-ward facing step coupling with quasi-square cavity. Stream function and vorticity forms of Navier-Stokes equation is adopted as a mathematical model. The flow field structures with different Reynolds number of 214.2, 418.4, 642.6 are computed respectively, the simulation results of transient flow and stead flow field are presented in the forms of stream traces. Parts of the velocity distribution profile along the horizontal and vertical cross-section are also demonstrated. The effects of different Reynolds numbers to the flow field are analyzed. Particle image velocimetry (PIV) technique is used to investigation of the flow field experimentally. The resulting velocity vectors plots of PIV measuring is agreement with that of numerical simulation. Both the investigation of finite element simulation and PIV experiment indicate that the flow field of around back-ward facing step coupling with a quasi-square cavity is complex, the flow field has the feature of mixing of back-ward facing step and lid-driven square cavity flow. The result of this studies have references significant for practical engineering application.

Key words: Finite element method, Back-ward facing step, Particle image velocimetry(PIV), Quasi-square cavity, Stream trace, Velocity vector