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arXiv 1809.07008physics.comp-ph
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浸没动边界耦合LBM-DEM问题的综合研究

A comprehensive study of coupled LBM-DEM with immersed moving boundary

G. C. Yang, L. Jing, C. Y. Kwok, Y. D. Sobral

摘要:

采用浸入式移动边界技术,对将格子玻尔兹曼方法(LBM)和离散元方法(DEM)耦合起来的全分辨流体-颗粒模型进行了系统的研究。在过去的十年中,已经报道了类似的算法,然而,主要模型参数的作用尚未得到充分理解。为了检查各种数值误差,进行了一系列基准情况下,从一个单一的静止粒子到多个移动粒子的雷诺数范围很广。据发现,对于低和中等雷诺数的流动,每一个颗粒直径20个流体细胞是必要的,以达到足够的精度(5%以内)。对于高雷诺数的流动,应采用湍流模型,以便能够以准确有效的方式捕获未分辨小涡流的影响。此外,LBM-DEM结果对弛豫时间也很敏感,特别是在空间分辨率不够的情况下。大的弛豫时间可以将流体动量的额外扩散引入流体-颗粒系统中,导致流体动力学相互作用减弱。通过选择大于下限0.5的小的弛豫时间,可以以计算工作为代价实现小的流体压缩性误差和流体与颗粒之间的强耦合。测试案例也表明LBM-DEM的能力来描述颗粒悬浮液的流变学捕获孔尺度的流体动力学相互作用。最后,为快速建立高质量的LBM-DEM模型提供了指导。

英文摘要:

A systematic study is carried out on a fully resolved fluid-particle model which couples the Lattice Boltzmann Method (LBM) and the Discrete Element Method (DEM) using an immersed moving boundary technique. Similar algorithms have been reported in the past decade, however, the roles of major model parameters are yet to be fully understood. To examine various numerical errors, a series of benchmark cases with a wide range of Reynolds number are performed, starting from a single stationary particle to multiple moving particles. It is found that for flow with low and intermediate Reynolds numbers, 20 fluid cells per one particle diameter are necessary to achieve sufficient accuracy (within 5%). For a flow with high Reynolds number, a turbulence model shall be incorporated so that the effects of unresolved small eddies can be captured in an accurate and efficient manner. Besides, the LBM-DEM results are also sensitive to the relaxation time, especially when the spatial resolution is inadequate. A large relaxation time can introduce additional diffusion of fluid momentum into the fluid-particle system, leading to weakened hydrodynamic interactions. By choosing a small relaxation time greater than the lower limit 0.5, a small fluid compressibility error and a strong coupling between fluids and particles can be achieved, at the cost of computational effort. The test cases also demonstrate the capability of LBM-DEM to describe the rheology of particle suspensions by capturing the pore-scale hydrodynamic interactions. Finally, a guideline for quickly establishing a high-quality LBM-DEM model is provided.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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