Numerical simulation of cavitation surge and vortical flows in a diffuser with swirling flow

Bin Ji*, Jiong Wang, X. Luo, K. Miyagawa, L. Z. Xiao, X. Long, Yoshinobu Tsujimoto

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

36 Citations (Scopus)


The strong swirling flow at the exit of the runner of a Francis turbine at part load causes flow instabilities and cavitation surges in the draft tube, deteriorating the performance of the hydraulic power system. The unsteady cavitating turbulent flow in the draft tube is simplified and modeled by a diffuser with swirling flow using the Scale-adaptive simulation method. Unsteady characteristics of the vortex rope structure and the underlying mechanisms for the interactions between the cavitation and the vortices are both revealed. The generation and evolution of the vortex rope structures are demonstrated with the help of the iso-surfaces of the vapor volume fraction and the Qcriterion. Analysis based on the vorticity transport equation suggests that the vortex dilatation term is much larger along the cavity interface in the diffuser inlet and modifies the vorticity field in regions with high density and pressure gradients. The present work is validated by comparing two types of cavitation surges observed experimentally in the literature with further interpretations based on simulations.

Original languageEnglish
Pages (from-to)2507-2514
Number of pages8
JournalJournal of Mechanical Science and Technology
Issue number6
Publication statusPublished - 2016 Jun 1


  • Cavitating flow
  • Cavitation
  • Cavitation surge
  • Draft tube
  • Swirling flow

ASJC Scopus subject areas

  • Mechanics of Materials
  • Mechanical Engineering


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