Comparison of Sewage Treatment Mixer in Three Pool Face Boundary Conditions

The method for setting the boundary condition of the pool surface was studied. Using the FLUENT 6.3 CFD software,the RNG k-e turbulence model and SI MPLE algorithm,the sewage treatment pool where a submersible mixer with two leaves was numerically simulated by describing the surface as wall,VOF model and rigid-lid assumption respectively. Meanwhile, the velocity distribution in the pool was analyzed. The results showed that: the contribution of the three different treatments to the flow in the pool are small except the area near the pool surface. In the first case ( describe the surface as wall), pool surface fluid velocity is zero, which is inconsistent with the actual situation obviously. In the other two cases (describe the surface as VOF model and rigid-lid assumption), the pool surface fluid velocity has the same velocity and is not zero,which is consistent with the actual situation. In the case of rigid-lid assumption,convergence was reached easily,and it is undemanding for the computer configuration,so it ( rigid-lid assumption) is the best boundary conditions setting method for the surface and provides guidance for the mixer numerical simulation.