多驱动对流传热问题的耗散粒子动力学研究
发布时间：2018-11-24 20:46
【摘要】：近年来,随着新兴技术的出现和高速发展,流体动力学面临复杂流体和复杂流动两大挑战。在新技术背景下,复杂流体流动可能是多物理场引起的,一种物理效应、一种化学效应甚至一种生物效应都可能成为驱动流体流动的因素,多种驱动力及其非线性耦合使得流动问题和与流动伴随的传热问题呈现复杂性、多样性和非线性,因而需要对流动的微观结构和传输过程进行深入分析。作为一种拉格朗日型粒子法,能量守恒的耗散粒子动力学方法(energy-conserving dissipative particle dynamics,e DPD)对这类具有多种驱动力的复杂流体流动与传热问题具有很大的潜力,这种新兴的介观方法应用在传热领域不过十来年时间,而且发展相对缓慢,可谓方兴未艾,还有很大的开拓空间。因而本文采用耗散粒子动力学方法研究了多种驱动力耦合的流动与传热现象。首先,本文系统地阐述了e DPD方法应用于流动与传热现象模拟的理论基础,利用动理论方法得到了e DPD流体系统所满足的质量守恒定律、动量守恒定律和能量守恒定律。此外,本文详细地阐述了耗散粒子动力学模拟的相关细节问题,包括边界处理、积分方法和参数选取问题,首先提出一种可行性的方案建立了耗散粒子动力学方法中介观参数与宏观输运系数之间的联系。根据方案,模拟了剪切力、浮升力单独驱动的库艾特流动和简单方腔内的自然对流问题,得到的结果分别与分析解和有限体积法模拟的结果吻合很好。剪切力是工程应用中强化传热的重要措施,因而这种剪切力与浮升力引起的混合对流问题引起了学者的极大兴趣。简单方腔内混合对流问题前人做过详细的研究,然而工程中考虑复杂形状很有必要。本文将耗散粒子动力学方法应用于内置椭圆热源的等温封闭方腔内的、剪切力与浮升力引起的、简单流体的流动与传热问题。首先研究了自然对流和顶盖驱动流,将模拟得到的结果与其他方法如有限体积法(finite volume method,FVM)、格子玻尔兹曼方法(lattice Boltzmann method,LBM)、微分求积法(differential quadrature method,DQM)等方法进行了比较,得到了比较一致的结果,验证了程序的正确性。接着在此基础上研究了横向剪切和纵向剪切引起的混合对流问题。发现横向剪切力引起的混合对流和纵向剪切力引起的混合在流动与传热特征上具有较大的差异。生物磁流体作为近年来比较热门的复杂流体之一,引起了众多学者的关注。在非等温和非均匀磁场作用下,生物磁流体受到开尔文力和洛伦茨力以及浮升力三者的共同影响,其动力学行为既不同于普通的铁磁流体力学(ferrohydrodynamics,FHD),又不同于一般的磁流体力学(magnetohydrodynmics,MHD)。本文首次将DPD方法用于研究半环形区域内的生物磁流体热磁对流问题。研究了磁数、哈特曼数、瑞利数、普朗特数对半环形区域内温度场和流场的影响,发现非均匀磁场下的热磁对流呈现与纯自然对流不同的特征。在外磁场下,左右两侧原来由于自然对流形成的两个旋涡会分别分裂成两个较小的旋涡,并且区域内存在三个热羽流,而纯自然对流只出现一个热羽流。对于受多种驱动因素影响的流体系统,在一定条件下,随着驱动力相对大小的变化,系统呈现不同的亚稳态的结构。DPD方法是一种有效可靠的数值方法,能够用来求解复杂形状内的受多种因素影响的对流传热问题,帮助发现一些新的有趣的物理现象,未来在研究复杂流动与传热问题时将起到重要作用。
[Abstract]:In recent years, with the emergence and high-speed development of emerging technologies, the fluid dynamics are facing the challenges of complex fluid and complex flow. in that context of a new technology, the flow of complex fluid may be caused by a multi-physical field, a physical effect, a chemical effect, or even a biological effect, may be a factor in the flow of the drive fluid, The various driving forces and their non-linear coupling make the flow problems and the heat transfer problems associated with the flow to be complex, diverse and non-linear, so the micro-structure and the transmission process of the flow need to be analyzed in-depth. As a Lagrangian particle method, the energy-conservation dissipative particle dynamics (e DPD) has a great potential for complex fluid flow and heat transfer problems with a plurality of driving forces, And the development is relatively slow, it can be said to be in the ascendant, there is still a lot of open space. In this paper, the dissipation particle dynamics method is used to study the flow and heat transfer phenomena of various driving force coupling. First, this paper systematically describes the theoretical basis of the e DPD method applied to the simulation of flow and heat transfer phenomena. The law of mass conservation, the law of conservation of momentum and the law of energy conservation of the e DPD fluid system are obtained by using the dynamic theory. In addition, the related details of dissipative particle dynamics simulation are described in detail in this paper, including boundary treatment, integral method and parameter selection. First, a feasible scheme is proposed to establish the relationship between the mesoscopic parameter and the macro transport coefficient of the dissipative particle dynamics method. According to the scheme, the problems of the flow of the shearing force and the floating-lift force and the natural convection in the simple square cavity are simulated, and the results are in good agreement with the results of the analysis and the finite volume method. The shear force is an important measure to strengthen the heat transfer in the engineering application, so the mixed convection problem caused by the shearing force and the uplift force is of great interest to the scholars. The mixed convection in the simple square cavity has been studied in detail. However, it is necessary to consider the complex shape in the engineering. In this paper, the kinetic method of the dissipative particle is applied to the problem of flow and heat transfer of simple fluid, which is caused by the shearing force and the uplift force in the isothermal enclosure of the built-in elliptical heat source. The simulation results are compared with other methods, such as the finite volume method (FVM), the lattice Boltzmann method (LBM) and the differential quadrature method (DQM). the result of the comparison is obtained, and the correctness of the program is verified. Then, the mixed convection problem caused by transverse shear and longitudinal shear is studied. It was found that the mixed convection and the longitudinal shear induced by the transverse shear forces have a great difference in the flow and heat transfer characteristics. As one of the most popular complex fluids in recent years, the bio-magnetic fluid has attracted many scholars' attention. Under the action of non-uniform and non-uniform magnetic field, the biological magnetic fluid is influenced by the Kelvin force and the Lorentz force and the uplift force, and the dynamic behavior of the magnetic fluid is different from that of the general ferrofluid dynamics (FHD), and is different from the general magnetic fluid dynamics (MHD). In this paper, the DPD method is used to study the thermal and magnetic convection of the bio-magnetic fluid in the semi-circular region. The effects of the number of magnetic numbers, the number of Hartmann, the number of Rayleigh and the Planck number on the temperature field and the flow field in the semi-annular region are studied, and the characteristics of the thermal and magnetic convection under the non-uniform magnetic field are found to be different from the pure natural convection. In the outer magnetic field, the two vortices, which are formed by natural convection, are split into two smaller vortices, respectively, and there are three hot-plume flows in the region, while the pure natural convection only occurs with one plume. For fluid systems affected by various driving factors, under certain conditions, with the change of the relative size of the driving force, the system presents different metastable structures. The DPD method is an effective and reliable numerical method, which can be used to solve the convection heat problem which is influenced by various factors in complex shape, and help to find some new and interesting physical phenomena, and will play an important role in the study of complex flow and heat transfer problems in the future.
【学位授予单位】：哈尔滨工业大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TK124
本文编号：2354992
[Abstract]:In recent years, with the emergence and high-speed development of emerging technologies, the fluid dynamics are facing the challenges of complex fluid and complex flow. in that context of a new technology, the flow of complex fluid may be caused by a multi-physical field, a physical effect, a chemical effect, or even a biological effect, may be a factor in the flow of the drive fluid, The various driving forces and their non-linear coupling make the flow problems and the heat transfer problems associated with the flow to be complex, diverse and non-linear, so the micro-structure and the transmission process of the flow need to be analyzed in-depth. As a Lagrangian particle method, the energy-conservation dissipative particle dynamics (e DPD) has a great potential for complex fluid flow and heat transfer problems with a plurality of driving forces, And the development is relatively slow, it can be said to be in the ascendant, there is still a lot of open space. In this paper, the dissipation particle dynamics method is used to study the flow and heat transfer phenomena of various driving force coupling. First, this paper systematically describes the theoretical basis of the e DPD method applied to the simulation of flow and heat transfer phenomena. The law of mass conservation, the law of conservation of momentum and the law of energy conservation of the e DPD fluid system are obtained by using the dynamic theory. In addition, the related details of dissipative particle dynamics simulation are described in detail in this paper, including boundary treatment, integral method and parameter selection. First, a feasible scheme is proposed to establish the relationship between the mesoscopic parameter and the macro transport coefficient of the dissipative particle dynamics method. According to the scheme, the problems of the flow of the shearing force and the floating-lift force and the natural convection in the simple square cavity are simulated, and the results are in good agreement with the results of the analysis and the finite volume method. The shear force is an important measure to strengthen the heat transfer in the engineering application, so the mixed convection problem caused by the shearing force and the uplift force is of great interest to the scholars. The mixed convection in the simple square cavity has been studied in detail. However, it is necessary to consider the complex shape in the engineering. In this paper, the kinetic method of the dissipative particle is applied to the problem of flow and heat transfer of simple fluid, which is caused by the shearing force and the uplift force in the isothermal enclosure of the built-in elliptical heat source. The simulation results are compared with other methods, such as the finite volume method (FVM), the lattice Boltzmann method (LBM) and the differential quadrature method (DQM). the result of the comparison is obtained, and the correctness of the program is verified. Then, the mixed convection problem caused by transverse shear and longitudinal shear is studied. It was found that the mixed convection and the longitudinal shear induced by the transverse shear forces have a great difference in the flow and heat transfer characteristics. As one of the most popular complex fluids in recent years, the bio-magnetic fluid has attracted many scholars' attention. Under the action of non-uniform and non-uniform magnetic field, the biological magnetic fluid is influenced by the Kelvin force and the Lorentz force and the uplift force, and the dynamic behavior of the magnetic fluid is different from that of the general ferrofluid dynamics (FHD), and is different from the general magnetic fluid dynamics (MHD). In this paper, the DPD method is used to study the thermal and magnetic convection of the bio-magnetic fluid in the semi-circular region. The effects of the number of magnetic numbers, the number of Hartmann, the number of Rayleigh and the Planck number on the temperature field and the flow field in the semi-annular region are studied, and the characteristics of the thermal and magnetic convection under the non-uniform magnetic field are found to be different from the pure natural convection. In the outer magnetic field, the two vortices, which are formed by natural convection, are split into two smaller vortices, respectively, and there are three hot-plume flows in the region, while the pure natural convection only occurs with one plume. For fluid systems affected by various driving factors, under certain conditions, with the change of the relative size of the driving force, the system presents different metastable structures. The DPD method is an effective and reliable numerical method, which can be used to solve the convection heat problem which is influenced by various factors in complex shape, and help to find some new and interesting physical phenomena, and will play an important role in the study of complex flow and heat transfer problems in the future.
【学位授予单位】：哈尔滨工业大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TK124
【参考文献】
相关期刊论文 前1条
1 刘谋斌;常建忠;;耗散粒子动力学处理复杂固体壁面的一种有效方法[J];物理学报;2010年11期
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