Developments in how the boundary layer lower the pipe drag reduction in transport of dense paste

AbstractWall slip phenomenon occurs near the inner wall of pipe when dense paste is transported, and it reduces the frictional resistance loss and saves energy. To determine how the boundary layer influences the flowing law, more pipe transporting tests have been performed. Taking coal slime as test material, water and PEO (plasma electrolytic oxidation) were injected into the boundary layer part. Many factors, such as mass concentration, pipe diameter, flow velocity, boundary layer thickness, were systematically studied on their changes influencing pressure loss. The pressure loss decreases exponentially with the increase of boundary layer thickness. Drag reduction effect of PEO as the injecting liquid is better than water, and the pressure loss declines about 20%. The smaller the pipe diameter, lower flow rate, and the more obvious the drag reduction effect will be.