Flows of sand-water slurries in horizontal pipes are commonly encountered in many environmental and industrial engineering applications. Pressure gradient and concentration distribution have been the most serious concern of researchers, dictating the selection of pump capacity and being used to determine several parameters of interest. Experimental investigations of such flows can encounter considerable technical difficulties, especially in determining the solids concentration. The measurements depend strongly on the type of instrumentation used (Kaushal \& Tomita [Powder Technol, Vol 172, 177-187, 2007]) and in practice, expensive \gamma-ray absorption techniques are needed to provide meaningful data. On the other hand, simplified models based on a global formulation are a powerful tool for estimating the pressure gradient, but they don’t provide information about the concentration distribution, and they cannot be extended to more complex flows. CFD has therefore been a commonly-used approach in recent years. The Mixture Model is computationally cheap, but limited to small particles and often not very accurate (Kaushal et al [Int J Multiphase Flow, Vol 43, 85-100, 2012]). Two-Fluid models based on KTGF perform better, but appear to be very unstable numerically, as well as computationally expensive (Ekambara et al [Ind Eng Chem Res, Vol 48, 8159-8171, 2009]). Here we present a Two-Fluid model for predicting the flow of sand-water mixtures in horizontal pipes. The main focus is the proper modeling of the following key features: phase diffusion induced by turbulence; effect of multiple particles on the drag force; and wall boundary conditions for the particle phase. The model, robust and numerically stable, compared to a granular-flow model requires only a relatively coarse grid and considerably less computer time to procure converged solutions; consequently, it looks particularly attractive for the applications. The model predictions are validated by comparison with the experimental data of Gillies et al [Can J Chem Eng, Vol 85, 1060-1065, 2004]. The agreement between computations and measurements is rather good in terms of both concentration distribution and pressure gradient.

Flow of sand-water mixtures in horizontal pipes

MESSA, GIANANDREA VITTORIO;MALAVASI, STEFANO;
2012

Abstract

Flows of sand-water slurries in horizontal pipes are commonly encountered in many environmental and industrial engineering applications. Pressure gradient and concentration distribution have been the most serious concern of researchers, dictating the selection of pump capacity and being used to determine several parameters of interest. Experimental investigations of such flows can encounter considerable technical difficulties, especially in determining the solids concentration. The measurements depend strongly on the type of instrumentation used (Kaushal \& Tomita [Powder Technol, Vol 172, 177-187, 2007]) and in practice, expensive \gamma-ray absorption techniques are needed to provide meaningful data. On the other hand, simplified models based on a global formulation are a powerful tool for estimating the pressure gradient, but they don’t provide information about the concentration distribution, and they cannot be extended to more complex flows. CFD has therefore been a commonly-used approach in recent years. The Mixture Model is computationally cheap, but limited to small particles and often not very accurate (Kaushal et al [Int J Multiphase Flow, Vol 43, 85-100, 2012]). Two-Fluid models based on KTGF perform better, but appear to be very unstable numerically, as well as computationally expensive (Ekambara et al [Ind Eng Chem Res, Vol 48, 8159-8171, 2009]). Here we present a Two-Fluid model for predicting the flow of sand-water mixtures in horizontal pipes. The main focus is the proper modeling of the following key features: phase diffusion induced by turbulence; effect of multiple particles on the drag force; and wall boundary conditions for the particle phase. The model, robust and numerically stable, compared to a granular-flow model requires only a relatively coarse grid and considerably less computer time to procure converged solutions; consequently, it looks particularly attractive for the applications. The model predictions are validated by comparison with the experimental data of Gillies et al [Can J Chem Eng, Vol 85, 1060-1065, 2004]. The agreement between computations and measurements is rather good in terms of both concentration distribution and pressure gradient.
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/11311/727572
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