Multiscale simulations of fluidized beds should account for the effect of sub-grid structures on drag. How to extract the features of these structures in the form of proper finite quantities, namely markers, has posed great challenges in mesoscale drag modeling. The choice of markers has seldom been investigated in terms of their rationality and adequacy. This article introduces a two-step scheme that is applied in the classic experimental approach to reflect on the choice of markers. The steady-state definitional relations of the drag correction factor are deduced from force balance equations, with emphasis on the difference between definitional relations and constitutive relations. A comparison between common drag models obtained from fine-grid simulations and corresponding definitional relations shows that the challenge in developing a general mesoscale drag model cannot be circumvented by correlating the heterogeneity index or drift velocity with the solid volume fraction, slip velocity, and gas-phase pressure gradient.

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关于中尺度拖曳标记的选择

流化床的多尺度模拟应考虑子网格结构对阻力的影响。如何以适当的有限量即标记的形式提取这些结构的特征，对中尺度阻力建模提出了很大的挑战。标记的选择很少根据其合理性和充分性进行研究。本文介绍了在经典实验方法中应用的两步方案，以反映标记的选择。阻力修正因子的稳态定义关系是从力平衡方程推导出来的，重点是定义关系和本构关系的区别。