Modeling and simulation of agglomeration in turbulent particle-laden flows: A comparison between energy-based and momentum-based agglomeration models
Modeling and simulation of agglomeration in turbulent particle-laden flows: A comparison between energy-based and momentum-based agglomeration models
复制标题
DOI：
10.1016/j.powtec.2015.12.034
复制
发表时间：
2016-06-01
影响因子：
5.2
通讯作者：
Breuer, M.
中科院分区：
文献类型：
--
作者：
Almohammed, N.;Breuer, M.
本文在具有确定性碰撞检测的硬球模型框架下，采用两种不同的建模方法：基于能量的团聚模型和基于动量的团聚模型，研究了剪切流中颗粒的团聚。前者是进一步改善有关团聚条件。此外，这两个模型的应用领域扩展到全三维湍流应用大涡模拟技术。在这里，颗粒被假定为刚性的，干燥的和静电中性的，因此只考虑由于范德华力的凝聚力。首先，基于能量和基于动量的团聚模型成功地验证了理论结果的基础上，使用现有的层流测试用例。数值计算结果与理论计算结果吻合较好。然后，利用这两种凝聚方法研究了垂直充分发展槽道湍流中颗粒凝聚的动力学过程。报告使用这两种团聚模型所获得的结果的详细比较。此外，这两种技术的性能检查的影响下，不同的正常恢复系数的粒子间的碰撞。此外，包括三个子模型（颗粒对流体的反馈效应，升力和亚网格尺度模型的颗粒）的团聚过程的影响进行了研究。结果表明，一个显着降低团聚率观察到，如果考虑的子模型。其次，应用附聚模型来评估初级颗粒直径和壁面粗糙度对附聚行为的影响。颗粒直径的减小导致更强的内聚脉冲，并因此导致更高的附聚速率。壁粗糙度增强了颗粒-颗粒碰撞，并略微增加了团聚过程的数量，从而导致更高的团聚速率。对比研究清楚地表明，两个模型预测的团聚过程的物理行为的趋势相似，但他们的结果略有偏离对方。两种模型的数值结果之间观察到的差异的最重要的原因进行了讨论。基于这两种模型的优点和缺点，在这项研究中强调，可以得出结论，由于减少了经验参数的必要性和更精确的结果，基于动量的团聚模型是优于基于能量的模型上级。(C)2016爱思唯尔B. V.保留所有权利。
In the present work, the particle agglomeration in shear flows is investigated in the framework of a hard sphere model with deterministic collision detection employing two different modeling approaches: the energy-based and the momentum-based agglomeration models. The former is further improved concerning the agglomeration conditions. Moreover, the application area of both models is extended towards fully three-dimensional turbulent flows applying the large-eddy simulation technique. Here, the particles are assumed to be rigid, dry and electrostatically neutral and hence only the cohesion due to the van-der-Waals forces is considered. First, the energy-based and the momentum-based agglomeration models are successfully validated based on theoretical results using an existing laminar test case. The numerical results are found to be in close agreement with the theory. Then, both agglomeration approaches are used to investigate the dynamic process of the particle agglomeration in a vertical fully developed turbulent channel flow. A detailed comparison of the results obtained using both agglomeration models is reported. Additionally, the performance of both techniques is examined under the influence of varying normal restitution coefficients of the inter-particle collisions. Furthermore, the influence of the inclusion of three sub-models (the feedback effect of the particles on the fluid, the lift forces and the subgrid-scale model for the particles) on the agglomeration process is studied. The results show that a significantly lower agglomeration rate is observed if the sub-models are considered. Next, the agglomeration models are applied to evaluate the effect of the diameter of the primary particles and the wall roughness on the agglomeration behavior. The reduction of the diameter of the particles leads to a stronger cohesive impulse and hence to a higher agglomeration rate. The wall roughness enhances the particle-particle collisions and slightly increases the number of agglomeration processes leading to higher agglomeration rates. The comparative study clearly indicates that both models predict similar trends of the physical behavior of the agglomeration process, but their results deviate slightly from each other. The most important reasons for the differences observed between the numerical results of both models are discussed. Based on the advantages and drawbacks of both models highlighted in this study, it can be concluded that owing to the reduced necessity of empirical parameters and the slightly more accurate results the momentum-based agglomeration model is superior to the energy-based model. (C) 2016 Elsevier B.V. All rights reserved.