Images of vortex ropes could improve hydraulic machinery safety

Vortices swirling in fluids can make beautiful patterns, but they also can reduce hydraulic machinery safety. Specifically, cavitation vortex ropes can increase pressure fluctuations and decrease stability and performance in hydraulics.

Li et al. explore the generation and transformation of cavitation vortex ropes in swirling flows to help improve hydraulic instabilities in machinery. The paper extends previous experiments of vortex rope formation and development by looking at their effects in hydraulic machinery draft tubes.

“Few experimental studies have been conducted on vortex ropes in hydraulic machinery draft tubes owing to the complexity of the experimental system and the observational limitations,” said co-author Hongjie Wang.

Using a specially designed set up to see the vortex ropes in action, the researchers varied pressure conditions under different Reynolds and cavitation numbers. This allowed the researchers to capture the configuration and evolution of four different types of stable cavitation vortex ropes and two unstable transitions using a high-resolution camera.

The results showed cavitation vortex ropes formed differently as the Reynolds and cavitation numbers varied. The researchers summarized the combinations and their transitions.

“We hope this work provides some references to improve the hydraulic instabilities induced by cavitation vortex ropes in hydraulic machinery,” Wang said.

In the future, the researchers plan to investigate control strategies of cavitation vortex ropes to improve performance characteristics and reduce pressure fluctuations in hydraulic machines as well as develop simulations of the control mechanisms.

Source: “Spatio-temporal evolution mechanism of cavitation vortex ropes in a swirling flow,” by Deyou Li, Zhipeng Ren, Liang Yu, Qi Yang, and Hongjie Wang, Physics of Fluids (2021). The article can be accessed at https://doi.org/10.1063/5.0067735 .