CFD-DEM耦合模拟中拖曳力模型精度

CFD-DEM耦合方法已广泛应用于岩土流固耦合问题分析，其模拟准确性与其中用于处理颗粒-流体相互作用的拖曳力模型密切相关。为了探究拖曳力模型精度的影响因素，采用CFD-DEM耦合方法建立了水中单颗粒沉降数值模型，模拟中考虑了3种典型拖曳力模型以及多种颗粒尺寸，将模拟得到的最终沉降速度与经验公式预测结果进行对比，分析了不同颗粒雷诺数（Re_p）时3种拖曳力模型（Ergun、Wen和Yu模型，Di Felice模型，Hill和Koch模型）的模拟精度。结果表明，Ergun、Wen和Yu模型以及Di Felice模型的精度均随着Re_p的增大而降低，而Hill和Koch模型的精度随着Re_p的增大出现先升高后降低的趋势：一般情况下，当Re_p≤14以及Re_p>72时，3种拖曳力模型的精度从高到低顺序为Ergun、Wen和Yu模型> Di Felice模型> Hill和Koch模型；而当14< Re_p≤40时，Hill和Koch模型的精度最高，Di Felice模型的精度最低；当40<Re_p≤72时，3种拖曳力模型的精度从高到低顺序为Ergun、Wen和Yu模型>Hill和Koch模型>Di Felice模型。

Accuracy of Drag Force Models in the CFD-DEM Method

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.