Near-wall flow characteristics in pipe bend dense slurries: Optimizing the maximum sliding frictional power

Abstract

In conveying concentrated liquid–solid mixtures in pipelines oriented horizontally, gravitational settling promotes a concentration-rich layer of solids at the pipe invert that degrades the wall due to sliding (abrading) action against the wall. The current study investigates near-wall flow field characteristics and then obtains flow and geometry conditions using a response surface methodology (RSM) that minimizes the maximum sliding frictional power developed in the vicinity of a 90° horizontal bend for transporting a dense solid–liquid mixture. The liquid–solid flow field is mathematically modeled with a Eulerian–Eulerian approach using the realizable $k-\epsilon$ model with standard wall functions for turbulence modeling. The effect of several operating parameters such as solid concentration, mixture velocity, particle sizes, pipe diameters, and bend ratios on the near-wall flow field in the bend reveals useful insight relevant to the bend wall degradation by solid particles. A reduction of 28% in the maximum sliding frictional power is achieved with the optimized flow conditions within the operating range considered. The novel approach could be utilized in an apriori estimation of the erosion in bends for any particle-pipe wall material combination in the hydro transport of dense solids.