稠密气固两相撞击流微观多尺度结构特性及细观相间作用机理研究

Dense gas-solid two-phase opposed jets flow is a typical heterogeneous, multi-scale and multi-phase coupled complex system, which has been widely used in chemical plants. The multi-scale structure and the interphase interaction of both gas- and particle-phase play a significant role in the characteristics of heat and mass transfer, as well as chemical reactions of the entire system. However, the relevant research is still scarce. Thus the studies of microscopic multi-scale structural characteristic and microscopic interphase mechanism in dense gas-solid two-phase opposed jets flow are of great importance both in theory and practice..In view of this, this project investigates the characteristics of turbulent coherent structures of the opposed jets flow based on mesoscopic numerical simulation (DNS and LES) and high-fidelity PIV measurement, and explains the physical nature of flow instability of opposed jets. The simulation of dense particle flow based on discrete element method (DEM) is used to analyze the interparticle collisions and the particle agglomeration, and obtain multi-scale structural characteristics of dense particle phase. And then, the wavelet method is used to construct structural sub-grid scale model and Adaptive-Mesh-Resolution Large Eddy Simulation (AMR-LES). Finally, by coupling AMR-LES of gas-phase and DEM of particle-phase, a multi-scale numerical simulation platform, i.e., AMR-LES-DEM, can be established to analyze the microscopic mechanism of interphase interaction of dense gas-solid two-phase opposed jets, and provide theory and foundational models for design and optimization of the chemical plant as well as other key devices in process engineering.

过程工业装置中广泛应用的稠密气固两相撞击流是一个典型的非均匀、多尺度、多相耦合的复杂体系。其中，气相和颗粒相的多尺度结构及相间作用，决定了整个体系的传热、传质及混合反应特性，迄今为止，相关理论研究仍极为匮乏。因此，聚焦稠密气固两相撞击流的微观多尺度结构特性及细观相间作用机理开展深入研究，将具有重要的科学意义和应用前景。.鉴于此，本项目拟结合细观数值模拟（DNS、LES）和高分辨率PIV测量，研究单相撞击流湍流拟序结构，阐述撞击面不稳定性的物理实质；应用颗粒流DEM模拟，解析微观的颗粒间碰撞及团聚行为，获取稠密颗粒相多尺度结构特性；基于小波分析，构建结构化亚格子模型，耦合气相动态自适应网格大涡模拟和颗粒相DEM模拟，建立多尺度数值模拟方法（AMR-LES-DEM）；在此基础上，解析稠密气固两相撞击流的细观相间作用机理，构建以稠密气固两相撞击流为核心的化工过程装置的优化设计与调控理论。

本项目针对过程工业装置中广泛应用的稠密气固两相撞击流这一非均匀、多尺度、多相耦合复杂体系，聚焦稠密气固两相撞击流的微观多尺度结构特性及细观相间作用机理，对其强化传热、传质及混合反应的物理机制进行阐述，并发展了多尺度细观模拟方法和调控理论。.本研究首先从气相湍流撞击流微观拟序结构入手，综合细观数值模拟和高解析度PIV测量，结合拟序涡结构提取算法，对气相撞击流多尺度拟序结构特性进行了统计分析；利用有限时间李雅普诺夫指数（FTLE）解析了撞击流介观输运及混合路径；并提出基于本征正交分解（POD）的撞击流不稳定性分析方法，阐述了撞击面振荡和形变的物理机制。.在此基础上，应用颗粒流DEM模拟，结合自行开发的颗粒流撞击面结构分析算法，系统研究了稠密颗粒撞击流的颗粒宏观运动特性以及颗粒流撞击面的多尺度结构特性，获得了颗粒撞击流模式的演变规律，揭示了颗粒流撞击面的形成和调控机制。.之后，基于小波变换，提取了湍流亚格子相干涡结构，详细研究了其对颗粒统计特性的影响；以此为基础，结合差分滤波（DF, differential filter）模型，构建了基于小波分析的结构化颗粒所见流场亚格子速度模型；将其与流体大涡模拟相耦合，建立了动态自适应网格气固两相大涡模拟方法。.最后，以两相大涡模拟为基础，整合气相撞击流多尺度结构特性和稠密颗粒流运动特性，对稠密气固两相撞击流的相间作用机理进行了解析，获得了其强化传热传质的物理机制。