Threshold velocity to initiate particle motion in horizontal and near-horizontal conduits

• The developed model predicts fluid velocity needed to initiate motion of particle.
• Correlation is proposed to compute drag coefficient of particle at rest on surface.
• We used bootstrap method to quantify 90% confidence bounds of model's predictions.
• Velocity prediction envelopes of model cover experimental values for ~ 90% of data.
• Smaller errors are produced by our model compared to previous models.

To initiate the motion of a solid particle in a conduit, the velocity of the carrier fluid needs to exceed the threshold velocity for particle transport. Several models have been developed that predict such velocity. However, none of these models provide information regarding the confidence of these predictions. In this paper, a new semi-mechanistic model is introduced using force balances on a particle in the horizontal and vertical directions, and torque balance on a particle. A unique contribution of this paper is the use of the bootstrap method to quantify the uncertainty of the model's prediction. This information is used to compute the envelope of the threshold velocity predictions to within a predetermined confidence level. We compared the performance of our semi-mechanistic model to existing models using statistical analysis and parity plots. The comparison suggests that our semi-mechanistic model is accurate, and is capable of explaining the variation in the experimental data. The threshold velocity envelopes suggested by our model cover the experimentally-observed values for 92%, 90%, and 93% of the experimental data for hydraulic transport from a bed of solids, pneumatic transport from a bed of solids, and pneumatic transport from the bottom of the conduit, respectively.

We developed a semi-mechanistic model that predicts the threshold fluid velocity needed to initiate the motion of a solid particle. Our model was developed using force balances in the horizontal and vertical directions and torque balance, and a fitted correlation between the drag coefficient and the particle Reynolds number.Figure optionsDownload as PowerPoint slide