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The isolated mixed region (IMR) is gradually formed during stirring and reduces the mixing efficiency. The unsteady-state formation process of the IMR was modeled and its formation mechanism was analyzed. The rotating frequency of the impeller was optimized using the chaos mathematical theory to improve the stirring efficiency without increasing the power consumption. The calculated results demonstrate that the IMR is a coherent structure, and its formation process is based on the free shear effect of the mixed layer. The chaotic stirring method can accelerate the momentum dissipation process by 37% by eliminating the IMR, and increase the speed by up to 31%. Therefore, chaotic mixing can eliminate the IMR in a shorter time and lower the power consumption.

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It is widely concerned that the non-ideal design of characteristic parameters of throat pipe of jet pump leads to the low pumping efficiency. The paper studies the pumping efficiency of jet pump under different characteristic parameters through numerical calculation to determine the influences of single parameter on pumping efficiency. And the coupling influences of parameters are predicted through XGBoost technology. The research shows that the coupling relation between the pumping efficiency of jet pump and multiple characteristic parameters can be predicted with the accuracy of 98.83%. The reasonable choice of characteristic parameters can improve pumping efficiency by 23.6%. The research will help designers to look for the best coupling of jet pump parameters accurately through numerical calculation and machine learning technologies.