Large eddy simulation of the transient cavitating vortical flow in a jet pump with special emphasis on the unstable limited operation stage

Abstract

This paper studies the unsteady three-dimensional cavitating turbulent flow in a jet pump. Specifically, thefocus is on the unstable limited operation stage, and both the computational and experimental methods are used. In the experiments, the distribution of the wall pressure, as well as the evolution of cavitation over time, are obtained for a jet pump. Computation is carried out using the large eddy simulation, combined with a mass transfer cavitation model. The numerical results are compared with the experimental results, including the fundamental performances (the pressure ratio h and the efficiency η), as well as the wall pressure distribution. Both the experimental and computational results indicate that the evolution of the cavitation over time in a jet pump is a quasi-periodic process during the unstable limited operation stage. The annular vortex cavitation inception, development and collapse predicted by the large eddy simulation agree fairly well with the experimental observations. Furthermore, the relationship between the cavitation and the vortex structure is discussed based on the numerical results, and it is shown that the development of the vortex structures in the jet pump is closely related to the evolution of the cavitation. The cavitation-vortex interaction is thoroughly analyzed based on the vorticity transport equation. This analysis reveals that the cavitation in a jet pump dramatically influences the distribution and the production of the vorticity. The process of the annular cavitation inception, development, and collapse involves a significant increase of the vorticity.