Relationships and Mechanisms of Sand Grain Promotion on Nozzle Cavitation Flow Evolution: A Numerical Simulation Investigation

The objective of this study was to primarily investigate the effects of sand grains with different mean diameters and concentrations on cavitation flow development in a nozzle. One new solid-liquid-vapor three-phase coupling numerical method was presented and a cavitation model was changed to perform numerical simulations. Results indicated that sand grain-pure water-cavitation flow (SG-PW-CF) vapor contents were greater than in pure water-cavitation flow (PW-CF). Sand grains were found to promote cavitation flow development, with the concentration promotion range becoming smaller with increased mean diameter. The mechanisms for these effects were explored and revealed as well. In SG-PW-CF, cavitation nuclei number was greater and tensile stress was also greater than in PW-CF. The maximum and absolute minimum slip velocities and maximum and minimum turbulent kinetic energies of SG-PW-CF were greater than in PW-CF. These effects on SG-PW-CF evolution were large, involving primary factors. The calculated magnitude of the Saffman lift force in SG-PW-CF was small (10(-2)), with its effects relatively weak and it was thus a secondary factor. Effects of variations of flow fields were more significant than force changes. In SG-PW-CF, variations of a single parameter with the concentration could not reflect the alternating relationships of vapor content with the concentration. Indeed, it was a combination of variations of all parameters.