Modelling segregation of bidisperse granular mixtures varying simultaneously in size and density for free surface flows
Modelling segregation of bidisperse granular mixtures varying simultaneously in size and density for free surface flows
复制标题
DOI：
10.1017/jfm.2021.342
复制
发表时间：
2021-05-11
影响因子：
3.7
通讯作者：
Lueptow, Richard M.
中科院分区：
文献类型：
--
作者：
Duan, Yifei;Umbanhowar, Paul B.;Lueptow, Richard M.
流动的粒状材料由于颗粒尺寸（由渗流驱动）和密度（由浮力驱动）的差异而分离。模拟大/重颗粒和小/轻颗粒的混合物的分离是具有挑战性的，由于两个分离机制的相反效果。使用离散元法（DEM）模拟相结合的尺寸和密度偏析，我们表明，偏析速度是很好地描述了一个模型，线性依赖于当地的剪切速率和二次上的自由表面流的物种浓度。浓度分布预测通过将这种偏析速度模型到一个连续的对流扩散偏析运输模型匹配DEM模拟结果以及广泛的颗粒尺寸和密度比。最令人惊讶的是，DEM模拟和分离速度模型都表明，在一定尺寸和密度比范围内的分离方向取决于当地物质浓度。这导致了一种方法来确定颗粒尺寸比，密度比和颗粒浓度的组合，对于该组合，双分散混合物将不会分离。
Flowing granular materials segregate due to differences in particle size (driven by percolation) and density (driven by buoyancy). Modelling the segregation of mixtures of large/heavy particles and small/light particles is challenging due to the opposing effects of the two segregation mechanisms. Using discrete element method (DEM) simulations of combined size and density segregation we show that the segregation velocity is well described by a model that depends linearly on the local shear rate and quadratically on the species concentration for free surface flows. Concentration profiles predicted by incorporating this segregation velocity model into a continuum advection-diffusion-segregation transport model match DEM simulation results well for a wide range of particle size and density ratios. Most surprisingly, the DEM simulations and the segregation velocity model both show that the segregation direction for a range of size and density ratios depends on the local species concentration. This leads to a methodology to determine the combination of particle size ratio, density ratio and particle concentration for which a bidisperse mixture will not segregate.