Interaction of Particles and Near-Wall Lift in Slurry Pipelines

In pipeline transport of slurries, it is desirable that the solid particles should be suspended by the fluid phase. Within the body of the flow, turbulent diffusion promotes suspension, but this mechanism is not effective near the lower boundary. Under certain conditions, near-wall fluid lift can provide the necessary support for the particles. The Kutta-Zhukovski equation is used to relate the lift force to the shape of the fluid velocity profile. Comparison with experimental findings shows that this lift may be associated with profiles of solid concentration that show a decreased concentration as the bottom of the pipe is approached. Observed reductions of pressure gradients result from this "off-the-wall" lift force. In certain instances, the slurry pressure gradient is found to be less than that for the "equivalent fluid," with favorable implications for pipeline economics.