Some key issues of unsteady turbulent numerical simulation in axial-flow pump

In order to predict the unsteady flow feature in axial-flow pump, the Reynolds-averaged Navier-Stokes (RANS) method and large eddy simulation (LES) method are used to perform the 3D unsteady turbulent simulation. The key issues in the simulation including the turbulence model, interaction between suction box and impeller, pressure fluctuation distribution pattern and pressure amplitude spectrum are investigated. It is found that LES could give more accurate simulation result over other turbulence models. The flow pattern at the suction box outlet is not uniform if the interaction between the suction box and impeller is considered. The velocity at the side of suction box near the inlet is larger than other areas. The ununiformity is quite different from the conventional supposition in which the flow at impeller inlet is considered to be uniform in the design and analysis of axial-flow pump. The investigation also shows that the sampling time should not be less than eight rotating cycles in order to ensure the capture of all the dominated frequencies of pressure fluctuations. The pressure amplitude increases gradually along the radius at the impeller region, and it decreases gradually along the radius after the outlet of guide-vane.