Water-sediment swirling flow is ubiquitous in rotating machinery. The centrifugal field drives the liquid outward and generates intense azimuthal shear, which in turn enhances the relative motion between water and sediment. The influence of the rotational effect on the velocity distribution of the two phases, particularly the relationship between vortex intensity and interphase slip velocity, has not yet been fully clarified. Based on PIV (particle image velocimetry) experiments, measurements were conducted on a dilute water-sediment two-phase flow with a magnetic stirrer rotating at 400–800 r/min and sediment particles ranging in size from 20 to 150 μm. The experimental results indicate that in the water-sediment swirling flow system, under the same rotational speed and particle size, the circumferential distribution of the time-averaged velocity of the water-sediment two-phase flow exhibits strong uniformity across the azimuth, while the radial distribution shows a trend of first increasing and then decreasing with increasing r/R. Overall, the slip velocity decreases with increasing r/R, and larger values typically appear in the regions with a larger rotation-rate tensor magnitude or higher fluid velocity. The peak time-averaged velocity and St (Stokes number) of the two phases increase with increasing rotational speed and particle size, and the turbulence intensity of the particle phase is higher than that of the liquid phase. Furthermore, there is a significant positive correlation between ‖Ω‖F2, which characterizes the vortex strength, and the relative slip velocity, indicating that greater vortex strength tends to enhance the relative motion between particles and the fluid.
Zhang et al. (Sun,) studied this question.