Numerical study of two types of rough groove in suppressing the tip clearance cavitation

Tip clearance cavitation (TCC) which is consisted of tip leakage vortex (TLV) cavitation and gap cavitation (occurs inside the gap region) is a common phenomenon in the gap flow filed in axial turbomachinery, and can trigger a series of negative effects. Based on the suppression mechanism of a type of prototypical horizontal casing groove, two types of rough groove structures are proposed in this paper aiming at enhancing the suppression effect on the TCC by utilizing the Coanda effect of the gap leakage jet. The gap flow field is generated via a NACA0009 hydrofoil and a solid wall. The gap size is fixed as 2 mm. The numerical simulation method is adopted. The results show that combining the detached-eddy simulation (DES) approach, SchnerrSauer cavitation model and a type of varRhoTurbVOF method on the OpenFOAM platform, accurate numerical results of cavitating gap flow fields under the small gap conditions can be obtained. The gap flow field analysis reveals that the control ability of the grooves on the leakage flow is enhanced via divergent- convergent flow passage in the roughness groove cases. The leakage rate is reduced while the local turbulence intensity is increased, which weakens the TLV and the tip separation vortex (TSV) dramatically. The rough casing grooves show a superior suppression effect on the TCC. The present work can inspire new casing treatment method for improving the anti-cavitation performance in the axial-flow hydraulic machinery.