The effect of the clearance geometries on the cavitating vortices near the foil tip

Abstract

The blade tip clearance is inevitable for an axial flow rotor. The clearance flow contains various vortices and the resulting vortex cavitation is a concern in hydraulic machineries. In the narrow gap, the vortex features are sensitive to the change of the clearance size, and then the geometry factors may influence the vortex cavitation characteristics. As a simplification of a blade, an isolated hydrofoil is convenient for adjusting the clearance geometries in different cases. The effects of the clearance shape, gap height and gap width on the cavitating vortices are discussed in present paper. As the limited space and the cavitation phenomenon make it difficult to measure the vortex flow features, the numerical simulation is widely used to investigate the cavitating vortices. An improved cavitation model, which is suitable for the vortex cavitation, is used in present work. Under the different geometrical conditions, the vortex structures, the pressure features and the cavitation characteristics are revealed from the simulation.