Experimental study on fluctuating hydrodynamics around axisymmetric bodies

Inception cavitating flows around axisymmetric bodies with different headforms, including the blunt, conical, and hemispherical objects are studied, based on experiments and numerical simulations. In order to accurately capture the vortex separation structure, a filter-based turbulence model (FBM) is used in numerical simulations. Meanwhile, a high-speed video camera and Particle Image Velocimetry (PIV) are used to visualize the inception cavitating flow structures, and to measure the velocity and vorticity fields. Both experimental and numerical results show that the headforms have significant impact on the inception cavitation flows. For the axisymmetric bodies with blunt and conical headforms, the inception cavitation number is much larger than that of the hemispherical one. In the inception cavitation condition, for the blunt and conical bodies, the high shear vortex structures locate in the shoulder area, and the inception cavity appears in the boundary layer separation zone near the wall instead of the adherent area. Here, the inception cavitation flow field reflects the vortex characteristics, while the high-fluctuating region and lower velocity area relates to the cavitation area. But for the hemispherical, the inception cavitation flow is very stable, and the sheet cavity attaches to the wall surface.