Gas flow through static particle arrangements with a channel: Resolved simulations and analytic considerations
Gas flow through static particle arrangements with a channel: Resolved simulations and analytic considerations
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DOI：
10.1016/j.cesx.2019.100015
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发表时间：
2019-05
影响因子：
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通讯作者：
A. Vila;S. Sanjeevi;Jt Johan Padding;S. Pirker
中科院分区：
文献类型：
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作者：
A. Vila;S. Sanjeevi;Jt Johan Padding;S. Pirker
致密气固体系中颗粒聚集体的破裂是一种常见的现象，特别是在粘性粉末和非球形颗粒互锁的情况下，颗粒聚集体的破裂会导致颗粒结构的显著不均匀性。在这项工作中，我们调查的影响，这种不均匀性的水动力阻力通过研究理想的情况下，一个随机排列的球体与通道状的空隙区域。更具体地说，我们引入这种异质性的均匀的颗粒排列，通过移动分开两个散装区域，这样的空隙通道划分颗粒散装。单弛豫时间格子玻尔兹曼模拟进行解决流体流动通过这样的被捕粒子配置，并计算相应的气体-颗粒的动量交换和压降。计算的随机球排列的固体上的阻力是在良好的协议与以前报道的结果Hill等人。（2001 b），Tenneti等人（2011）和Tang et al.（2015年）。然而，整体的动量交换得到的配置包含的异质性是显着较低的。显然，通道允许相当大量的流的旁路，导致降低的总压降，从而低估流化床中的最小流化速度。基于这些直接的数值模拟，我们研究了整体的压降依赖于特征长度尺度（即宽度）的通道状的异质性L c，表面雷诺数（30 <$Re <$300），和固体的体积分数在密集（即散装）区域（0.4 <$p <$0.55）。通道的宽度在颗粒直径Dp的数量级内变化（1 μ L c/Dp ≤ 4.36），降低了总固体体积分数（0.25 μ L c/0.55）。除了数值模拟，我们推导出（半）解析相关的致密散装区域以及通道。由于模拟范围从层流到过渡流，因此提供单一压降相关性非常具有挑战性。因此，我们根据计算的表面雷诺数选择适当的关联式来估计通道压降。对于层流，我们实现了一个很好的协议之间的组合（即散装和通道）分析预测的整体压降和我们解决的数值模拟。在过渡区，压降值更难以预测，当我们接近湍流区时，两者的一致性更好。我们相信，这项工作可以作为一个基础，为未来的阻力法律占通道样的子网格的不均匀性的发展。
Fractures of particle assemblies happen frequently in dense gas-solid systems leading to a notable heterogeneity in the particle configuration, especially in case of cohesive powders and non-spherical particle interlocking. In this work, we investigate the influence of such heterogeneities on the hydrodynamic drag by studying the idealized case of a random arrangement of spheres with a channel-like void region. More specifically, we introduce this heterogeneity to a homogeneous particle arrangement by shifting apart two bulk regions, such that a void channel divides particle bulk. Single-relaxation-time lattice Boltzmann simulations were performed to resolve fluid flow through such arrested particle configurations and calculate the corresponding gas-particle momentum exchange and pressure drop. The calculated drag forces acting on the solids for random sphere arrangement are in good agreement with previously reported results of Hill et al.(2001b), Tenneti et al.(2011), and Tang et al.(2015). However, the overall momentum exchange obtained for configurations containing a heterogeneity is significantly lower. Obviously, the channel allows for a by-passing of a considerable amount of the flow leading to a reduced overall pressure drop and thereby underestimating the minimum fluidization velocity in a fluidized bed. Based on these direct numerical simulations, we examine the overall pressure drop dependence on the characteristic length scale (ie width) of the channel-like heterogeneity L c, the superficial Reynolds number (30⩽ Re⩽ 300), and the solid volume fraction in the dense (ie bulk) region (0.4⩽ ϕ p⩽ 0.55). The width of the channel is varied within the order of magnitude of particle diameter D p (1⩽ L c/D p⩽ 4.36), decreasing an overall solid volume fraction (0.25⩽ ϕ⩽ 0.55). In addition to the numerical simulations, we derive (semi)-analytic correlations for the dense bulk region as well as for the channel. As the simulations range from laminar to transitional flow, providing a single pressure drop correlation is very challenging. Therefore, we estimate the channel pressure drop with the appropriate correlations selected according to calculated superficial Reynolds number. For laminar flow, we achieved a good agreement between a combined (ie bulk and channel) analytical prediction of overall pressure drop and our resolved numerical simulation. In the transitional regime, the pressure drop values are more difficult to predict, with the better agreement as we approach the turbulent regime. We believe that this work can act as a basis for the development of future drag laws accounting for channel-like sub-grid heterogeneities.