Application and experiment of different turbulence models for simulating tip leakage vortex in axial flow pump

Abstract: In order to explore a turbulence model to simulate the structure and the kinetic characteristic of the tip leakage vortex suitably, the study was conducted based on the ANSYS CFX soft and high-speed imaging experiment. The topology structure of the simulation domain was optimized with 20 layers in a blade tip region that got more flow information in the tip area. As a result, simulation requirements are met, while reducing the calculation time. The flow field characteristic, especially the tip leakage vortex simulated by four kinds of turbulence models, which are standard k-ε, renormalization group k-ε, standard k-ω, and shear stress transport k-ω, was compared and analyzed. The simulation and the experiment results showed that the external characteristic curve predicted basing on the SST k-ω model is in substantial agreement with the experiment curve, and the deviation of the head is about 4.7% in the operating condition, which is better than the others; Head error based on standard k-ω model had a little less than others. The distribution law of the streamlines of the tip leakage vortex predicted basing on the four models was similar, as well as the pressure field and the axial velocity in the blade tip area. However, the length of the low-pressure area computed by RNG k-ε was longer than other 3 models. The counter velocity narrow region based on the RNG k-ε and SST k-ω was bigger than others, and the vortex entrainment was stronger too. The identification of the vortex core based on vortex intensity was established and compared with the results by the high-speed imaging. The motion trajectory of the tip leakage vortex based on different turbulence was different. It moves up when simulated in a big working operation. The motion trajectory of the tip leakage vortex based on SST k-ω is in substantial agreement with the experiment by comprehensive comparison. Via the above study, the adaptability of the SST k-ω model in the tip leakage vortex simulation was determined to be the best turbulence model among these four turbulence models, so the SST k-ω model is recommended when studying the tip leakage vortex in axial flow pumps.