【作者】 孙刚；

【导师】 胡俊杰； 叶想平；

【作者基本信息】 中国地质大学 ， 资源与环境（安全工程）（专业学位）， 2024， 硕士

【摘要】 非等温颗粒两相流广泛存在于自然界和工程应用中,如污染物控制、化学反应器、火山喷发和森林火灾。在室内污染物控制和街谷火灾中涉及颗粒运动和温度变化,是典型的方腔内非等温颗粒两相流问题。因此,研究方腔内非等温颗粒两相流的规律,能够为理解、预测和控制颗粒运动提供一些新认识,同时为室内污染物控制策略的制定和街谷火灾风险降低提供理论支撑。格子Boltzmann方法具有清晰的物理背景,计算效率高和易于处理颗粒-流体相互作用,已成为广大学者研究非等温颗粒两相流的重要工具。目前,一些学者对非等温颗粒两相流进行了一些研究,但对方腔内非等温颗粒运动的认识并不充分。因此,本文采用格子Boltzmann方法对方腔内非等温颗粒两相流进行研究。本文主要内容如下:(1)研究了强制对流与热对流在协同作用和对抗作用下方腔内非等温单颗粒运动的规律,并讨论了颗粒初始位置、雷诺数(Re)、瑞利数(Ra)和颗粒尺寸对颗粒运动的影响。结果表明,在协同和对抗作用下,稳态后颗粒运动的轨迹对其初始位置不敏感。随着Re和Ra的增大,在协同作用下,颗粒运动状态有2种;而对抗作用下流场结构更复杂,由于涡旋行为的影响,在不同Re下,颗粒运动状态有6种,不同Ra下,颗粒运动状态可以分为5种,这里存在临界Re和Ra。在颗粒尺寸的研究中,从离心力和壁面斥力的作用机制对颗粒运动状态进行了分析。(2)研究了强制对流与热对流在协同作用下方腔内非等温颗粒群运动的规律,讨论了颗粒初始间距、Re、Ra和颗粒尺寸对颗粒运动的影响。结果表明,颗粒初始间距越大,颗粒运动越靠近方腔中心,而颗粒尺寸对颗粒运动的影响与之相反。非等温颗粒群的运动与强制对流和热对流的强度有关,随着Re增大,颗粒运动先朝方腔中心收缩,然后向边界扩散,而热对流增强,颗粒运动更复杂。(3)在强制对流与热对流对抗作用下,研究了颗粒初始间距、Re、Ra和颗粒尺寸对方腔内非等温颗粒群运动规律的影响。结果表明,随着颗粒初始间距和Re的增大,颗粒运动先靠近方腔中心后又远离。随着Ra增大,热对流主导的涡旋发展,颗粒运动被推向方腔的左上方。在不同颗粒尺寸下,较小尺寸颗粒的运动更靠近方腔中心,而较大尺寸颗粒的运动离方腔边界更近。通过对强制对流与热对流在协同和对抗作用下方腔内非等温单、多颗粒运动的研究,揭示了颗粒运动规律、颗粒-流体相互作用和颗粒-颗粒相互作用的机理,对于室内污染物控制和街谷火灾防控具有重要理论意义与价值。更多还原

【Abstract】 Non-isothermal particle-laden flows are widely found in nature and in engineering applications such as pollutant control,chemical reactors,volcanic eruptions and forest fires.The problem of two-phase flow of non-isothermal particles in a square cavity is typical in indoor pollutant control and street-valley fires involving particle motion and temperature changes.Therefore,the study of the laws of two-phase flow of nonisothermal particles in square cavities can provide some new insights into understanding,predicting and controlling particle motion,as well as provide theoretical support for the development of indoor pollutant control strategies and fire risk reduction in street valleys.The lattice Boltzmann method,with its clear physical background,computational efficiency and ease of dealing with particle-fluid interactions,has become an important tool for a wide range of scholars in the study of non-isothermal granular two-phase flows.At present,some scholars have conducted some studies on non-isothermal particle two-phase flow,but the motion of non-isothermal particles in the square cavity is not well understood.Therefore,in this thesis,the lattice Boltzmann method is used to investigate the two-phase flow of non-isothermal particles in a square cavity.The main contents of this thesis are as follows:(1)The laws governing the motion of non-isothermal single particles in a cavity under the synergistic and antagonistic effects of forced convection and thermal convection are investigated,and the effects of the initial position of the particles,the Reynolds number,the Rayleigh number,and the size of the particles on the motion of the particles are discussed.The results show that the trajectory of the post-steady-state particle motion is insensitive to its initial position under synergistic and antagonistic effects.With the increase of Re and Ra,there are two kinds of particle motion states under the synergistic effect;while the flow field structure is more complicated under the antagonistic effect,due to the vortex behavior,there are six kinds of particle motion states under different Re,and the particle motion states can be classified into five kinds under different Ra,where the critical Re and Ra exist.In the study of particle size,the state of particle motion was analyzed in terms of the mechanism of centrifugal force and wall repulsion.(2)The laws of non-isothermal particle swarm motion in the cavity under the synergistic action of forced convection and thermal convection are investigated,and the effects of initial particle spacing,Re,Ra and particle size on particle motion are discussed.The results show that the larger the initial spacing of the particles,the closer the particle motion is to the center of the square cavity,while the particle size has the opposite effect on the particle motion.The motion of the non-isothermal particle population is related to the intensity of forced convection and thermal convection;as Re increases,the particle motion first shrinks toward the center of the square cavity and then spreads toward the boundary,while thermal convection is enhanced and the particle motion is more complicated.(3)The effects of initial particle spacing,Re,Ra,and particle size on the law of motion of the non-isothermal particle population in the square cavity were investigated under the counteracting effects of forced convection and thermal convection.The results show that as the initial spacing of the particles and Re increase,the particle motion first approaches and then moves away from the center of the square cavity.As Ra increases,a vortex dominated by thermal convection develops and the motion of the particles is pushed to the upper left of the square cavity.At different particle sizes,smaller sized particles move closer to the center of the square cavity,while larger sized particles move closer to the boundary of the square cavity.Through the study of non-isothermal single and multiple particle motions in the cavity under the synergistic and antagonistic effects of forced convection and thermal convection,the particle motion laws,particle-fluid interactions and particle-particle interactions mechanisms are revealed,which are of great theoretical significance and value for the indoor pollutant control and the prevention and control of fires in street valleys.更多还原