Study of Turbulent Kinetic Energy and Dissipation Based on Fractal Impeller

Abstract

Turbulent kinetic energy and turbulent dissipation are important aspects of the flow field characteristics, which can affect the wear and energy loss in mixing equipment. In order to increase equipment wear and energy loss in the mixing process, a series of fractal impellers were designed based on the fractal iteration method, and the effects of the fractal dimension and the number of iterations on the flow field characteristics were investigated. Firstly, the distribution characteristics of turbulent kinetic energy and its uniformity were studied. Then, the distribution characteristics of the turbulent dissipation rate were studied and interpreted using vortex analysis, and the mixing power of the device was further investigated. The results showed that: for the turbulent kinetic energy of the flow field, an increase in the fractal dimension and the number of iterations makes the turbulent kinetic energy intensity of the flow field decrease and the distribution more uniform, compared to the non-iterative impeller, specifically the rectangular secondary iterative impeller caused a 30% reduction in the turbulent kinetic energy intensity and a 50% increase in the uniformity; for the turbulent dissipation of the flow field, in general an increase in the fractal dimension reduces the turbulent dissipation in the flow field, and an increase in the number of iterations increases it slightly, this influence law is due to a change in the trailing vortex caused by the blade structure; and a change in the law of turbulent dissipation also causes a corresponding change in the stirring power, from the non-iterative impeller to a rectangular one iteration impeller, the power decreases by 20% while the average speed decreases by only 5%. In conclusion, the special boundary of the fractal iterative impeller can reduce the turbulent kinetic energy and turbulent dissipation of the flow field to a large extent, and its two characteristics, the fractal dimension and the number of iterations, affect the reduction effect. The results of the study can be used as a reference for the design of mixing equipment to reduce turbulent kinetic energy and turbulent dissipation.