Large eddy simulation and Euler–Lagrangian coupling investigation of the transient cavitating turbulent flow around a twisted hydrofoil

• Published in: International journal of multiphase flow 2018-03, Vol.100, p.41-56
• Main Authors: Long, Xinping, Cheng, Huaiyu, Ji, Bin, Arndt, Roger E.A., Peng, Xiaoxing
• Format: Article
• Language: English
• Subjects: Cavitating flow; Cavitation; Finite-time lyapunov exponent; Lagrangian coherent structures (LCSs); Vortical flow
• ISSN: 0301-9322; 1879-3533
• DOI: 10.1016/j.ijmultiphaseflow.2017.12.002

•Cavitation around a twisted hydrofoil is simulated by LES.•Cavitating vortical flow is analyzed by Euler–Lagrangian viewpoints.•Five groups of LCSs due to sheet/cloud cavitation transition are identified and discussed.•The relationship between velocity circulation and cavitation shedding dynamics is discussed. In the present paper, large eddy simulations combined with the Zwart cavitation model are conducted to simulate the transient cavitating turbulent flow around a Delft Twisted hydrofoil. Numerical results show a reasonable agreement with the available experimental data. A three dimensional Lagrangian technology is developed to provide an alternative method for the analyses in cavitating flow, which is based on Lagrangian viewpoint. With this technology, the track lines of re-entrant and side-entrant jets are straightforwardly displayed and clearly indicate that collisions of the mainstream, the re-entrant jet and the side-entrant jet play an important role in the primary and secondary shedding. The evolution of U-type structures and the interactions between cavitation and vortices are well captured and discussed in detail from the Eulerian viewpoint. The numerical results show that during the stage of attached cavity, the topology of the cavity leaves an important influence on the vortex structure. Once the cavity is cut off, the vortex structure evolution will affect significantly the local cavitating flow. Further analysis demonstrates that the lift acting on U-type structures, which is induced by velocity circulation around U-type structures, significantly affects the formation and the development of U-type structures. Lagrangian Coherent Structures (LCSs) obtained with the three dimensional Lagrangian technology are used to reveal the influence of U-type structures on local flow patterns and it shows that there is a close relationship between the local flow separation and vortex structures. Our work provides an insight into the interactions of cavitation-vortex in the cavitating flow around a twisted hydrofoil and demonstrates the potential of 3D LCSs in the analyses of cavitating flow. Five groups of LCSs are identified and discussed as the sheet/cloud cavitation shedding occurs periodically. [Display omitted]