Abstract

For the CFD simulation of slurry flow in horizontal pipeline, it is essential to ensure that the computation domain has sufficient length to allow the inlet effect to disappear and the flow to reach the fully developed state where the experimental measurement is usually made. The minimum value of this sufficient length is called entry length. However, the entry length used by different researchers spanned over a wide range. There is no consensus how long the entry length should be and a guideline for deciding the value of this entry length is needed. In this paper, using the Eulerian-Eulerian two fluid model (TFM) based on the kinetic theory of granular flow (KTGF), a series of steady state 3D CFD simulations are conducted to investigate the horizontal pipeline slurry flow entry length and its sensitivity to the various hydrometrics parameters. After the assessment of the grid-independence, a parametric study is carried out to investigate the effect of pipe diameter, mixture velocity, and solid volume concentration on the entry length by analyzing the deviations of pressure drop, hydraulic gradient, solid phase velocity and volume fraction between different cross suctions downstream the inlet. All the simulations are conducted with large and small pipe diameters, high and low mixture velocities, and high and low solid volume concentrations. Finally, depending on the level of computation accuracy and cost, the recommended entry length, in the form of pipe length/diameter (L/D) ratio, is provided.

Introduction

Slurry pipeline transport is an environment-friendly and efficient way to convey solid materials from one place to another. This method is most applied in short distance scenarios in mining, dredging, and drilling. Because the material transported is enclosed in the pipe, this method has almost no impact on the environment along the pipeline route.

For the slurry transport, there are two most concerned issues, i.e., the prediction for the critical transport velocity and the pressure drop. However, due to the complex behavior of the settling of the solid phase in the slurry, it is difficult to provide a theoretical analysis. In addition, building the corresponding experimental setup for a particular engineering application is always money and time consuming. Therefore, nowadays, the computational fluid computation (CFD) becomes as a powerful tool to achieve the goal of precise prediction for the hydrodynamic properties.

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