Local structural anisotropy prevails in gas–solid suspensions. It causes strong fluctuations in the drag on individual particles. In this work, the anisotropy of microstructures is quantified by a second‐order structure tensor, which is determined with a directionally dependent mean free path length. Direct numerical simulations of low‐Reynolds‐number flows past anisotropic and isotropic BCC, FCC, and random arrays of monodisperse spheres in sufficiently large domains are performed. The results show that, at the same solid volume fraction, the differences between the mean drag in principal directions of anisotropic arrays and that in isotropic arrays correlate well with functions of eigenvalues of the structure tensor for the anisotropic arrays. Anisotropic drag models for different arrays are proposed. Assessment of the model for random arrays shows that it well captures fluctuations in the mean drag at microscales of several sphere diameters, where the traditional model fails to give satisfactory predictions.

中文翻译：

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低雷诺数单分散气固悬浮液中各向异性微观结构对流体-颗粒阻力的影响

气固悬浮液中普遍存在局部结构各向异性。它会导致单个颗粒上的阻力发生剧烈波动。在这项工作中，微观结构的各向异性通过二阶结构张量来量化，该张量由方向相关的平均自由程长度确定。对经过各向异性和各向同性BCC，FCC的低雷诺数流进行直接数值模拟，并在足够大的区域内对单分散球体进行随机排列。结果表明，在相同的固相体积分数下，各向异性阵列主方向的平均阻力与各向同性阵列的平均阻力之间的差异与各向异性阵列的结构张量特征值的函数密切相关。提出了不同阵列的各向异性阻力模型。