Large eddy simulation of the tip-leakage cavitating flow with an insight on how cavitation influences vorticity and turbulence

Cavitation within a tip leakage flow remains a challenging issue in a variety of axial hydraulic machines. It is still not possible nowadays to predict cavitation occurrence in such a flow with acceptable accuracy. In the present study, we have carried out numerical simulations of a tip leakage cavi...

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Veröffentlicht in:Applied Mathematical Modelling Jg. 77; S. 788
Hauptverfasser: Cheng, HY, Bai, XR, Long, XP, Ji, B, Peng, XX, Farhat, M
Format: Journal Article
Sprache:Englisch
Veröffentlicht: New York Elsevier BV 01.01.2020
Schlagworte:
Cavitation
Computational fluid dynamics
Computer simulation
Energy dissipation
Evolution
Fluid flow
Hydrofoils
Kinetic energy
Large eddy simulation
Leakage
Local flow
Mathematical models
Stretching
Transport equations
Turbulence
Vortices
Vorticity
ISSN:1088-8691, 0307-904X
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Zusammenfassung:Cavitation within a tip leakage flow remains a challenging issue in a variety of axial hydraulic machines. It is still not possible nowadays to predict cavitation occurrence in such a flow with acceptable accuracy. In the present study, we have carried out numerical simulations of a tip leakage cavitating flow, generated by a straight NACA0009 hydrofoil. We have used the LES method combined with the Schnerr–Sauer cavitation model. The numerical results agree well with experimental data. The evolution of the tip leakage cavitating flow, involving tip-leakage vortex (TLV), tip-separation vortex (TSV) and induced vortex (IV), is analyzed from Eulerian and Lagrangian viewpoints. The results show that the spatial evolution of the tip leakage cavitating flow can be divided into three stages: Stage Ⅰ, Independent development of the TLV and TSV; Stage Ⅱ, Fusion of the TLV and TSV; and Stage Ⅲ, Development of the IV and dissipation of the TLV. The Lagrangian coherent structures (LCSs) obtained from the numerical results indicate that the TLV cavitation significantly influence the local flow patterns. The vorticity transport equation was then used to further analyze the influence of the cavitation on the vortices. The results demonstrate that the stretching term dominates the TLV evolution and the dilatation term is responsible for the vorticity reduction inside the TLV cavity. The results also show how the cavitation influences the local turbulence and that the transport term in the turbulent kinetic energy equation influences the turbulence distribution near the TLV cavity.
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ISSN:1088-8691
0307-904X
DOI:10.1016/j.apm.2019.08.005