Abstract: The CFD-DEM coupling method has been widely used in the modelling of fluid-solid interactions in geotechnical engineering. The accuracy of the CFD-DEM modelling is strongly influenced by the precision of the drag force models used to deal with particle-fluid interactions. In this study, the sedimentation of a single particle in water was modeled by using the CFD-DEM method, three typical drag force models and various particle sizes were considered in the simulations, the terminal sedimentation velocities of particles were obtained in the simulations and then compared with those predicted by a popular empirical model, and the influence of the particle Reynolds number (Re_p) on the accuracy of the drag force models was analyzed. The results show that the accuracies of both the Ergun, Wen and Yu model and the Di Felice model decrease, while the accuracy of the Hill and Koch model firstly increases and then decreases with the increasing of Re_p. Generally, when Re_p ≤ 14 and Re_p>72, the relative magnitudes of the accuracy of the three drag force models are as follows:Ergun, Wen and Yu model>Di Felice model>Hill and Koch model; However, when 14<Re_p ≤ 40, Hill and Koch model has the highest accuracy, while the Di Felice model has the lowest accuracy; When 40<Re_p ≤ 72, the relative magnitudes of the accuracy of the three drag force models are Ergun, Wen and Yu model > Hill and Koch model > Di Felice model.

Key words: discrete element method(DEM), computational fluid dynamics (CFD), drag force models, single particle sedimentation