基于团聚物聚并破碎动力学并耦合群平衡模型的气固系统粗网格连续介质模拟

量化气固流化床中介尺度结构的形成和动态演化规律对于发展可靠的计算流体力学模型和反应器的设计优化具有重要意义。本项目拟通过两相粒子图像测速、高分辨率离散颗粒模拟和理论分析相结合的方式研究流化床中团聚物时空动态演化特性，建立基于边界分割技术和自适应阀值的团聚物鉴别方法。进一步通过分析团聚物的湍动碰撞、流体的黏性剪切及湍流涡团撞击等多因素等对其动态演化的影响，以建立团聚物的聚合、破碎演化动力学模型，从而完善适用于气固流化床的团聚物群平衡模型（PBM）。在此基础上，结合能量最小多度（EMMS）曳力模型框架，量化团聚物动态行为和尺寸分布对亚格子本构关系尤其是相间曳力的影响。将群平衡模型和结构曳力以及双流体模型相结合，提出考虑介尺度动态演化影响的粗网格连续介质模拟方法，实现对气固流化床的准确高效模拟。本项目可以促进对气固流化床多尺度非均匀流动的深入理解，为工业流态化反应器的设计和优化提供理论基础。

Quantifying the formation and dynamic evolution of mesoscale structures in gas-solid fluidized beds is of great significance for the development of reliable computational fluid dynamics models and the optimization of reactor designs. Based on particle image velocimetry (PIV) technique, high-fidelity discrete particle simulation (DPM) and theoretical analyses, this project attempts to explore the dynamic evolution mechanisms of particle clusters. A novel method for identifying clusters based on the boundary tracking technique and adaptive threshold standard threshold is proposed. By analyzing the effects of cluster collisions, fluid shear and eddy-cluster impact on the dynamic evolution of particle clusters, the coalescence and breakage dynamic models as well as the population balance model (PBM) are developed. By incorporating the PBM and the energy minimization multiscale (EMMS) approach, a novel sub-grid drag correction model is further proposed to account for the effect of cluster size distribution (CSD) on the interphase interaction. Finally, a CFD-PBM-EMMS integrated model based on the Eulerian framework will be developed for modeling the gas-solid fluidized beds as well as the spatio-temporal dynamic evolution of mesoscale structure. Present study is expected to deepen the understanding of multiscale complexity of gas-solid flow, and lay solid foundation for the numerical simulation, design and optimization of large-scale fluidized reactors.