Prediction of drag coefficient and ultimate settling velocity for high-density spherical particles in a cylindrical pipe

In this paper, we build a model for calculating the drag coefficient and ultimate settling velocity of high-density and large-diameter solid particles in cylindrical pipes. The settling process of particles in a cylindrical pipe was recorded by using a high-speed camera. Based on the analysis of the experimental data, a gap area ratio was introduced into the model in order to predict the resistance coefficient and ultimate settling velocity of the particles settling in the open space, enabling the model to predict the resistance coefficient and ultimate settling velocity of spherical particles settling in cylindrical pipes. The values of the ultimate settling velocity and the drag coefficient that were obtained with the proposed formulas were validated using experimental data and computational fluid dynamics results. The model was found to be accurate and reliable.