Impact of fibers on pumping flow: an analysis by CFD-DEM simulations and experiments

Abstract

The quantitative studies on pumping flow of fiber particles are very rare. In this research, CFD-DEM simulations, as well as experiments, were conducted to investigate the flow field and fiber behaviors. The mass concentration of the fiber suspension was increased, starting gradually from 0.5 to 1.0% and ultimately reaching 1.5%. The velocity profiles at varying radius positions were obtained by PIV. The CFD-DEM reveals that fiber particles exert an inhibitory effect on swirling flows. Furthermore, the PIV data reveal that the velocity from suction to pressure surface of the blade decreases in a linear manner. The trend of variation in fiber suspension is similar to that observed in clean water. The external characteristic data reveal an improvement in efficiency as concentration increases, aligning with the flow profile variation. As the concentration grows from 1.0 to 1.5%, the peak efficiency turns down by a noticeable trend. To investigate this turning, high-speed photography was employed to capture the fiber behaviors. It was observed that the fibers cluster near the pressure surface of the blade. Then, the fiber clusters undergo deformation and ultimately disperse as they leave the channel. Therefore, the fiber aggregation exerts a destabilizing influence on the flow field, leading to a reduction in the pumping capacity.