Investigation on the multiphase sink vortex Ekman pumping effects by CFD-DEM coupling method
Investigation on the multiphase sink vortex Ekman pumping effects by CFD-DEM coupling method
复制标题
CFD-DEM耦合方法研究多相沉涡Ekman泵浦效应
DOI：
10.1016/j.powtec.2019.06.036
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发表时间：
2020-01-15
影响因子：
5.2
通讯作者：
Tan, Dapeng
中科院分区：
文献类型：
--
作者：
Li, Lin;Qi, Huan;Tan, Dapeng
气-液-固多相下沉涡是一种复杂的湍流力学现象，其中涉及到的Ekman边界层的抽吸效应具有重要的科学价值和工程意义。针对这一问题，提出了一种基于可实现k-ε湍流模型和软球模型的计算流体动力学与离散元耦合方法（CFD-DEM）模拟多相下沉涡。对气液耦合过程中的抽吸和抽气过程进行了分析，揭示了Ekman边界层的传质机理。在此基础上，研究了粒子被下沉涡吸入的现象，得到了Ekman泵效应。最后，研究了埃克曼抽运效应对不同密度颗粒的影响，验证了该方法的有效性和可靠性。数值结果表明，抽吸强度和抽气强度构成了一个依赖于初始扰动分量的数据集;液体边界层中存在明显的上涌现象，这是由Ekman边界层的螺旋耦合结构引起的。颗粒的Ekman抽吸过程分为三个典型阶段：Ekman抽吸-抽出阶段、Ekman水平抽吸阶段和Ekman上升阶段，其流型受初始扰动的控制，呈现复杂的非线性湍流特征;随着颗粒密度的增加，Ekman抽吸状态和水平抽吸状态的作用增强，颗粒的Ekman上升流效应明显减弱。(C)2019爱思唯尔B. V.保留所有权利。
The gas-liquid-solid multiphase sink vortex is a complex turbulent mechanical phenomenon, in which the pumping effects of Ekman boundary layer involved in the above process has the important scientific value and engineering significance. To address the matter, a coupled Computational Fluid Dynamic and Discrete Element Method (CFD-DEM) method for the simulation of the multiphase sink vortex is proposed based on the realizable k-epsilon turbulent model and the soft sphere model. The suction and extraction regularities of gas-liquid coupling process are analyzed to reveal the matter transfer mechanism of Ekman boundary layer. Then, the phenomenon for the particle sucked by sink vortex is investigated to obtain the Ekman pumping effects. Finally, the influences of Ekman pumping effects on particles with respect to different densities are studied to verify the validity and reliability of the proposed method. Numerical results demonstrate that the suction and extraction intensities constitute a data set that is dependent on the initial disturbance components; there is an apparent upwelling phenomenon in the liquid boundary layer, which is caused by the spiral coupling structure of Ekman boundary layer. The Ekman pumping process for particles has three typical stage: Ekman suction-extraction state, Ekman horizontal pumping state, and Ekman upwelling state, wherein the flow patterns are dominated by the initial disturbance and appear a complex nonlinear turbulence features; with the particle density increasing, the effects of Ekman suction-extraction state and horizontal pumping state are enhanced, but the Ekman upwelling effect for particle has apparent decreased. (C) 2019 Elsevier B.V. All rights reserved.