Transportation and accumulation processes of particles in fluid flows with DEM

本文提出了一种计算方法来预测三维自由表面流引起的大尺度固体的输运。MICS是基于不可压缩流的CFD方法，改进了配置网格中密度和质量守恒的处理。假定多相场包括固体和被自由表面隔开的液、气两相，是由不同物理性质的不可压缩、不可混溶的流体组成的。对压力方程的离散化进行了检验，得到了数值稳定的收敛结果。根据流体计算结果和离散元法（DEM）模型对颗粒的外力进行了计算。结果表明，用MICS可以很好地预测颗粒阻力系数和尾流。MICS应用于靠近侧壁的下落颗粒和在倾斜底面上移动的非均匀颗粒。结果表明，MICS对颗粒流的预测是有效的。此外，数值方法还可以预测均匀流动中球的瑞利-泰勒稳定性问题和阻力系数，以及多球随波动流动的水力实验结果。

A computational method has been developed to predict the transportation of large-scale solid bodies due to 3D free-surface flows. The MICS is based on the CFD method for incompressible flows, in which the treatment for density and mass conservation has been improved in the collocated grid. The multiphase field including solid bodies and liquid and gas phases separated by free surfaces is assumed to be consist of the incompressible and immiscible fluids with different physical properties. The discretization of pressure equations was examined to obtain the numerically stable converged results. The external forces for the particles are evaluated from the results of the fluid computations and a model of the distinct element method(DEM).It was shown that the particle drag coefficients and wake flows are successfully predicted with MICS. The MICS was applied to a falling particle near a side wall and non-uniform particles moving on the inclined bottom surface. As a result, it was demonstrated that MICS is effective to predict the particle-laden flows. Furthermore, it was shown that the numerical method enables us to predict Rayleigh-Taylor stability problem and drag coefficient of a sphere in a uniform flow as well as the results of hydraulic experiments related to the transportation of multiple spheres by the flow accompanied by wave motions.