多孔介质内三相流体流动与相变传热微观机理的格子Boltzmann方法研究

The three-phase fluid flow and phase-change heat transfer in porous media are widely encountered in energy, environment, chemical engineering, and so on. Due to the complexity of pore structures, the interaction among different fluid components, and the interaction between fluid and solid wall, the coupling between flow and phase-change heat transfer, the three-phase fluid flow and phase-change heat transfer in porous media are very complicated. The traditional methods are not suitable for studying this problem own to their limits. The lattice Boltzmann (LB) method based on mesoscopic kinetic theory is a promising approach for the study of such a complicated problem, but there are still some basic problems needed to be solved. In this project, we will develop the LB three-phase model that includes micro-scale effect and couples heat and mass transfer; construct microscopic boundary condition that can accurately describe the interaction between fluid and solid wall; analyze the effects of pore structure, wetting, capillary number, temperature on fluid interface dynamics and heat transfer performance, and further explore the microscopic mechanism and law of the three-phase fluid flow and phase-change heat transfer in porous media. This project not only provides a new and effective approach to study the problem of heat and mass transfer of the three-phase fluid in porous media, but also is of certain directive significance to the low permeability oil reservoir exploitation, greenhouse gas storage and droplet based micro-device optimizing.

多孔介质内三相流体流动与相变传热问题广泛存在于能源、环境、化工等诸多领域。由于涉及复杂的孔隙结构、不同流体组分以及流固间的相互作用、流动与相变传热的耦合，多孔介质中三相流体流动与相变传热机理极为复杂，传统的数值方法在研究这类问题时受到很大的限制。而基于介观动理学理论的格子Boltzmann（LB）方法是研究这类问题的有效方法，但目前仍然有一些关键基础问题急需解决。本项目拟针对此类复杂问题，发展考虑微尺度效应并耦合热质传输的三相流LB模型；建立准确刻画流体与固壁相互作用的微观边界条件；分析孔隙结构、润湿性、毛细数、温度对流体界面动力学行为和传热性能的影响，进而探究多孔介质中三相流体流动与相变传热的微观机理与规律。本项目不但为研究多孔介质中三相流体传热传质问题提供新的有效手段，而且对涉及这一基本问题的低渗透油藏的开发、温室气体的地下埋存及基于液滴技术的微流控芯片的优化均具有一定的指导意义。

多孔介质内三相流体流动与相变传热是一个涉及到多相多组分界面动力学又涉及热质输运的复杂系统，其广泛存在于能源、环境、化工等诸多领域。本项目提出采用基于气体动理学理论的格子Boltzmann（LB）方法，并结合GPU并行的高性能计算手段，对多孔介质内三相流体流动与相变传热的微观机理进行研究。本项目基本按照计划执行，并取得了一些研究成果，包括：（1）从描述多组分的Cahn-Hilliard方程出发，建立了追踪三相流体相界面的LB模型，并耦合不可压流体输运的LB模型，提出了刻画三相流体流动的相场LB方法；（2）发展刻画三相流体与固体壁面微观相互作用的润湿性边界条件，本项目从自由能泛函理论出发，给出了边界处序参数满足的微分方程，并进一步根据组分减少一致性原则建立了三相流体与固体相互作用的润湿性边界条件，且给出了边界处理的LB格式；（3）利用所提出的LB模型和润湿性边界条件对孔隙介质内多相流体输运问题开展了研究，包括单孔内多相流体相界面不稳定性问题、三相流体的亚稳态相分离现象、复杂孔隙内液滴动力学行为；（4）本项目基于稀疏矩阵算法，并结合CUDA编程技术设计了基于GPU的多相流LB方法的高效并行算法，为大规模开展多孔介质内三相流体流动与传热的LB模拟提供了可能。