气体动理学格式和颗粒动理学的流体颗粒两相流模型与相间作用机理研究

Numerical simulations and experiments of phase interactions of dense gas-solid two-phase flow will be conducted based on kinetic theories of gases and particles. In present project, the flow behavior of gas and particles will be measured using CMOS high speed camera in the horizontal channel, and the distributions of velocity and solid volume fraction will be measured with the flexible wall, rough wall and curved wall in the horizontal channel. Based on large eddy simulations, the unified gas-kinetic scheme (UGKS) will be proposed with the consideration of the momentum exchange of fluid and particles due to the collisions of particles. The transfer and dissipation of kinetic energy caused by fluid turbulence and collisional interactions are studied. The model for hydrodynamics of particles with the granular temperature and rotational granular temperature equations will be established based on kinetic theory of granular flow. The filtered turbulent model for solid phase is derived using density-weighted filtering. The relations of the sub-grid models of particles, including filtered models of viscosity and pressure of particles, will be correlated between the coarse-grid and the finer grid using the multi-grid method and the multirsolution analysis theory. The large eddy simulation for fluid and large eddy simulation of particles are used to investigate the turbulent structure and phase interaction in the dense gas and particles two-phase flow. The exchange and dissipations of momentum and kinetic energy between the fluid phase and the solid phase will be studied due to fluid turbulence and collisional interactions of particles. The stability of dense gas-particle two-phase flow will be investigated at the fluid turbulent mechanism and the collisions mechanism in the dense gas-solid two-phase flow. Present investigation will provide the foundation of heat and mass transfer as well chemical reactions in dense gas-solid two-phase flow systems.

本项目以气体动理论和颗粒动理论为基础，展开流体颗粒两相相间作用的理论和实验研究。应用CMOS高速摄像仪构建水平槽道气体颗粒两相流动实验平台，展开柔性壁面和粗糙壁面以及曲壁面流体颗粒流动实验。结合大涡模拟，建立考虑颗粒碰撞效应的流体与颗粒动量交换的气体动理学格式(BGK格式)模型，研究流体湍流对颗粒碰撞的脉动能量传递和耗散规律。以颗粒动理论为基础，获取包含颗粒拟温度和颗粒转动拟温度方程的颗粒流动模型。应用密度加权过滤，建立过滤的颗粒湍流控制方程。采用多分辨分析理论和多重网格方法，获取粗网格与细网格流动参数之间的变化规律，构建包括颗粒亚格子涡粘系数等的亚格子模型，形成流体颗粒两相湍流大涡模拟计算方法，研究流体颗粒两相湍流中湍流结构与颗粒的相互作用规律，揭示流体湍流和颗粒碰撞作用下气体颗粒流动过程稳定性，为流体颗粒两相流动、化学反应和传热传质研究奠定理论基础。

气固两相流动广泛存在于直升机悬停和化工、热能等工业生产实践中。气固两相流动在气体湍流和气固相间作用的影响下，呈现出明显的非均匀结构特征。在复杂的气固两相过程中，相间作用对气固两相流动的影响占主要地位。. 以格子-Boltzmann方法和颗粒动理学理论(kinetic theory of granular flow，KTGF)为基础，提出了一种考虑颗粒聚团影响的非均匀动态多尺度曳力模型，建立了颗粒微观尺度和聚团介观尺度的颗粒碰撞能耗的非均匀气固流动的多尺度能耗模型。. 研究三维两相沉降系统中不同密度比条件下稀相颗粒微观尺度和密相颗粒聚团介观尺度的两相流动，涵盖液固两相以及气固两相流动。研究发现在低密度比条件下没有形成明显的非均匀结构。在高密度比条件下，随着固相体积分数的增加，颗粒非均匀现象更加明显，颗粒所受的无量纲曳力和曳力系数增加。..应用非均匀动态多尺度气固相间曳力模型，获得了不同几何结构和物性参数的提升管内颗粒聚团的生成和破碎规律。发现瞬时当地加速度大于瞬时迁移加速度1-2个数量级。通过多尺度能耗对比，发现颗粒碰撞能耗与曳力能耗共同作用影响颗粒聚团的形成。. 对双提升管循环流化床和变截面循环流化床数值模拟发现变截面循环流化床调控颗粒聚团流动优于双提升管循环流化床，获得了双提升管和变截面循环流化床内流场特性和分布规律。发现较小的固储量会使得颗粒在双提升管循环流化床和变截面循环流化床中无法实现自循环。. 对悬停的直升机旋翼旋转引起的气体和颗粒的流动行为的模拟结果表明，旋转的叶片尖端产生涡旋，驱动旋流向下运动与颗粒层接触。随着叶片在颗粒层上方的悬停高度减小，气体携带的颗粒质量增加。. 项目研究形成了离散颗粒微观尺度和颗粒聚团介观尺度流动的新的多尺度相间作用力模型，揭示了非均匀气固流动中流体湍流、气固作用和颗粒碰撞对非均匀结构流动的协调控制作用，为实际工程气固反应器的设计和优化提供新理论分析方法。