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过程工程学报 ›› 2022, Vol. 22 ›› Issue (12): 1652-1665.DOI: 10.12034/j.issn.1009-606X.222036

• 研究论文 • 上一篇    下一篇

粗粒化CFD-DEM的离散松弛模型

余亚雄1,2， 段凡1,2， 张宇1,2， 周强1,2,3*   

  1. 1. 西安交通大学化学工程与技术学院，陕西 西安 710049 2. 新能源系统工程与装备陕西省高校工程研究中心，陕西 西安 710049 3. 西安交通大学动力工程多相流国家重点实验室，陕西 西安 710049
  • 收稿日期:2022-01-26 修回日期:2022-02-22 出版日期:2022-12-28 发布日期:2022-12-30
  • 通讯作者: 周强 zhou.590@mail.xjtu.edu.cn
  • 基金资助:
    国家自然科学基金

Discrete relaxation model for coarse-grained CFD-DEM

Yaxiong YU1,2,  Fan DUAN1,2,  Yu ZHANG1,2,  Qiang ZHOU1,2,3*   

  1. 1. School of Chemical Engineering and Technology, Xi'an Jiaotong University, Xi'an, Shaanxi 710049, China 2. Engineering Research Center of New Energy System Engineering and Equipment, University of Shaanxi Province, Xi'an, Shaanxi 710049, China 3. State Key Laboratory of Multiphase Flow in Power Engineering, Xi'an Jiaotong University, Xi'an, Shaanxi 710049, China
  • Received:2022-01-26 Revised:2022-02-22 Online:2022-12-28 Published:2022-12-30
  • Contact: Qiang Zhou zhou.590@mail.xjtu.edu.cn

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摘要： 采用粗粒化技术的计算流体力学-离散单元法(Coarse Grained Computational Fluid Dynamic and Discrete Element Method, CFD-CGDEM)可以减少计算量，有着广阔的工业应用前景。然而与CFD-DEM相比，CFD-CGDEM存在能量耗散速率偏低导致其计算的粒化温度和固相应力过大的问题。本工作基于均匀耗散系统的颗粒动理学理论构建了一种离散松弛模型(DRM)，该模型通过给相邻颗粒对之间施加耗散力的方式增强颗粒间的能量耗散速率。采用均匀耗散系统和鼓泡流化床对DRM粗粒化模型进行了验证，结果表明，与传统的粗粒化模型相比，采用DRM的CFD-CGDEM能够更准确地预估均匀耗散系统中粒化温度的演化过程；且在鼓泡床模拟中发现，与采用传统粗粒化模型或Yu等(Ind. Eng. Chem. Res., 2021, 60(15): 5651-5664)的松弛模型(RMF)相比，采用DRM的CFD-CGDEM可以得到与CFD-DEM更为接近的时均量。

关键词: 气固两相流, 流态化, CFD-DEM, 粗粒化, 松弛模型

Abstract: Direct application of computational fluid dynamics and discrete element method (CFD-DEM) in industrial applications is unfeasible due to the enormous number of particles. As a result, the coarse-grained CFD-DEM (CFD-CGDEM) is proposed, which could save time and money by lumping a cloud of real particles into a coarse particle. However, due to its under-prediction of collisional energy dissipation, CFD-CGDEM typically over-predicts granular temperature and solid stresses when compared to CFD-DEM. As a result, in CFD-CGDEM simulations, a coarse-grained model capable of increasing energy dissipation is necessary. This work developed a coarse-grained model called discrete relaxation model based on the granular kinetic theory in the homogeneous cooling system (HCSs). By putting dissipation forces on the particle-pair, the discrete relaxation model could increase the energy dissipation between them. The proposed model eliminates errors in the estimation of local average solid phase velocity and granular temperature, as compared to Yu et al.'s relaxation model (Ind. Eng. Chem. Res., 2021, 60(15): 5651-5664). A posteriori simulations on homogeneous cooling systems and bubbling fluidized beds were used to assess the proposed model. It was discovered that CGDEM with the proposed model produced a more accurate forecast of the instantaneous granular temperature in HCSs than CGDEM with the usual coarsening model which was unable to improve energy dissipation. Furthermore, when compared to CFD-CGDEM with Yu et al.'s model and that with usual coarsening model, CFD-CGDEM with the proposed model better reproduced the time-averaged fields generated by CFD-DEM simulation for the considered bubbling fluidized bed. This emphasized the significance of increasing energy dissipation in CFD-CGDEM simulations, as well as the potential of the proposed model to considerably increase simulation accuracy.

Key words: gas-solid flows, fluidization, CFD-DEM, coarseness, relaxation model