The spatio-temporal evolution of detailed cavitating vortex structures in an axial flow waterjet pump

The emergence of complex cavitating vortex flow creates a significant challenge to the safe and stable performance of axial flow waterjet pumps when it operates under extreme conditions. This paper aims to investigate the intricate structures of cavitation vortices and examine the interaction between cavitation dynamics and vortex evolution under typical vortical cavitation conditions. The temporal and spatial evolution of tip leakage vortex cavity (TLVC) cavitation at different cavitation indices are investigated. The Wedge-shaped cavity (WSC) first appears near the leading edge in the initial stage of cavitation (σ = 0.624). In the growing stage of cavitation (σ = 0.247), the interaction between the TLVC and WSC ultimately leads to the shedding of the perpendicular cavitating vortices cavity (PCVC). In the severe stage of cavitation (σ = 0.173), the PCVC in big scale and shedding cavity block flow passage and the head drops significantly. The tip leakage vortex cavitating flow at the rated operating point is simulated using large eddy simulation coupled with the Burgers vortex cavitation model. A comparative analysis of various vortex identification methods highlights their respective capabilities in capturing vortex structures. The spatial evolution of tip leakage vortices has three typical characteristics in different locations corresponding to generation, mergence, and dissipation, respectively. Finally, the analysis of each term in vorticity transport equation shows that the stretching term is the most prominent factor. This study is of great significance for improving the understanding of cavitating flow mechanisms and enhancing the performance of axial flow waterjet pump operating under extreme conditions.