Drag plays a crucial role in hydrodynamic modeling and simulations of gas–solid flows, which is significantly affected by particle Reynolds number, solid volume fraction, heterogeneity, granular temperature, particle‐fluid density ratio, and so on. To clarify and quantify the multiscale effects of these factors, large‐scale particle‐resolved direct numerical simulations of gas–solid flows with up to 115,200 freely moving particles are conducted. Both domain‐averaged kinetic properties and local averaged dimensionless drag are sampled and analyzed. It is revealed that the complex scale‐dependence of drag is attributed to the multiscale effects of heterogeneous structures and particle fluctuating velocity. The granular temperature and the scalar variance of solid volume fraction are also found to be scale‐dependent. On account of these, a new drag correlation as the function of Froude number is proposed with consideration of scale‐dependence.

中文翻译：

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气固两相流中与尺度和结构有关的阻力

阻力在气-固流动的流体动力学建模和模拟中起着至关重要的作用，这受颗粒雷诺数，固体体积分数，非均质性，颗粒温度，颗粒-流体密度比等的显着影响。为了阐明和量化这些因素的多尺度影响，进行了具有多达115,200个自由运动粒子的气固两相流的大规模粒子分解直接数值模拟。均对区域平均动力学特性和局部平均无量纲阻力进行了采样和分析。结果表明，阻力的复杂尺度依赖性归因于异质结构和颗粒脉动速度的多尺度效应。还发现颗粒温度和固体体积分数的标量变化与比例有关。由于这些原因，