Based on the finite volume method and Realizable k-ε turbulence model, the flow field inside multinozzle jet pumps was investigated numerically. The calculation reliability was validated by experimental data. Based on the simulation results of streamwise and spanwise vorticity distribution and their peak value variation, the mixing mechanism of the two fluids was analyzed. The results show that the multinozzle could promote the mixing and improve pump efficiency. The vortex has great effects on the mixing. Relative to the streamwise vorticity, the spanwise vorticity value is large and the attenuation becomes flat. The streamwise vortex plays a major role in the mixing. The value and attenuation rate of streamwise vorticity determine the effect of the mixing in the throat. For a definite vorticity value, the greater the streamwise vorticity value is, the faster it decays. The smaller the spanwise vortex size, the faster the mixng, and the higher the pump efficiency. The vorticity distribution in the throat indicates a central nozzle may lead to greater losses. The optimum distribution is that all the nozzles are on a circle.
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