Simplified Numerical Model for Transient Flow of Slurries at Low Concentration

Rapid transients are particularly dangerous in industrial hydro-transport systems, where solid-liquid mixtures are transported via long pressure pipelines. A mathematical description of such flow is difficult due to the complexity of phenomena and difficulties in determining parameters. The main aim of the study was to examine the influence of the simplified mixture density and wave celerity description on satisfactory reproduction of pressure characteristics during the transient flow of slurry at low concentrations. The paper reports and discusses the selected aspects of experimental and numerical analyses of transient slurry flow in a polyethylene pipe. The experiments were conducted by using the physical model of a slurry's transportation pressure. The aim of the experiments was to determine the wave celerity during a transient flow in slurries. A low concertation of slurries, which was used during experiments, is typical for one of the biggest slurry networks in Poland. A comparison of the effects of different wave celerity descriptions was performed. The research reported that the theoretical formulas for slurry wave celerity and mixture density were not sufficiently accurate to obtain satisfactory compliance between calculations and observations. To improve the model, the experimental values of wave celerity and the concept of equivalent mixture density have been applied to indirectly consider the influence of variable mixture parameters. With such modifications, the calculated pressure characteristics in all analyzed episodes demonstrated satisfactory compliance with observations. The simplified approach proved to be effective in properly reproducing the intensity and frequency of rapid pressure changes.