Experimental investigation of the particle distribution of gas-solid turbulent flow in the boundary layer

Abstract

By the three-dimensional and no-contact optical technique digital holography, the particle distributions of a turbulent gas-solid boundary layer were studied in a fully developed horizontal channel, and the velocity field of the gas phase was obtained by particle image velocimetry (PIV) with main upstream speeds of Uh=2.1ms−1, 5.2ms−1, and 8.74ms−1. Carborundum powders with diameters of 38μm and 60μm were used as the particle phase and titanium dioxide nanoparticles were used as ghost particles. It was found that the peak of the particle distribution occurs in a logarithmic region. With an increase of particle size, the peak shifts toward the wall. As the velocity increases, the peak shifts toward the channel center. The gravity and sweeps have influence on the particle motion toward the wall; particle–wall collisions, ejections and the Magnus lift force have influence on the particle motion toward the channel center. Through analysis of the velocity field and shear strain distribution in the gas boundary layer, the existence of sweeps and ejections caused by quasi-flow vortices has been confirmed. Meanwhile, it was found that the peak of shear strain occurred near the wall and that wall-normal fluctuation and shear strain under high flow rate were significantly higher than at low flow rate; these characteristics were consistent with the distribution of particles in the boundary layer.