【作者】 陈胜；

【导师】 郑楚光； 施保昌；

【作者基本信息】 华中科技大学 ， 热能工程， 2005， 博士

【摘要】 随着科技的飞速发展,大规模科学与工程计算在科学研究和工程应用中的地位越来越重要,被公认为是科学研究中与实验和理论研究方法同等重要的第三种方法。流体运动的仿真模拟一直是大规模科学与工程计算的最为重要的领域之一,也是一个非常具有挑战性的课题。近年来,格子Boltzmann 方法已经发展成为模拟流体流动以及为复杂物理现象建模的一个新工具。与以宏观连续方程为基础的传统计算流体力学方法不同,格子Boltzmann 方法是基于流体微观模型和介观动力论方程的方法。与传统的计算流体力学方法相比,格子Boltzmann 方法具有许多独特的优势,如编码简单、边界条件容易实现、具有完全并行性等。格子Boltzmann 方法的这些特点吸引了许多领域的学者和工程技术人员,目前格子Boltzmann 方法已经在多相流、多孔介质流、悬浮粒子流、反应流、磁流体力学和生物力学等领域取得了很大的成功,已经成为流体力学模拟的一类重要方法。但是,格子Boltzmann 方法发展至今还存在一些不足。例如在本学科内对燃烧的模拟,非均匀网格下相间作用力的处理、气固多相流的双向耦合等问题,国内外相关的研究非常少。为了促进格子Boltzmann 方法在本学科的应用,我们作了一些有益的尝试,为相关工作的深入展开奠定了必要的基础。首先,我们对现有的格子Boltzmann 方法外力模型进行了概述。讨论了不同外力模型的优缺点。由于在格子Boltzmann 方法中外力项的处理与反应源项的处理思路相同,所以外力处理模型的讨论对格子Boltzmann 方法在多相流动和化学反应中的应用有非常重要的意义,但奇怪的是到目前为止还缺乏对此方向较全面的总结。我们将以此为基础展开相应的研究工作,包括边界条件对外力模型的影响,外力模型中各项对应的物理意义及适用范围。其次,我们构造了一种处理气固多相流双向耦合的格子Boltzmann 模型。其思想是基于分而治之的策略:使用格子Boltzmann 方法模拟气相,而颗粒相则通过颗粒的运动方程求解。与已有的模拟气固多相流的格子Boltzmann 模型相比,该模型首次考虑了气固多相流中两相间的耦合处理,因而适用范围更广。并且这种Euler-Lagrange体系使得格子Boltzmann 方法的优点得到充分发挥。更多还原

【Abstract】 Large Scale Computation (LSC) has been becoming more and more important in scientific studies and engineering applications with the development of science and technology, and is well recognized as a significant method in addition to the experimental and theoretical approaches. Fluid flows simulation is one of the most important and challenging branches of Large Scale Computing. Recently, the Lattice Boltzmann Method (LBM) has developed into a new tool for simulating fluid flows and modeling complicated physical phenomena. Unlike the traditional Computational Fluid Dynamics (CFD) methods based on macroscopic continuum equations, LBM is based on microscopic model or mesoscopic kinetics equations. Compared with the traditional CFD methods, LBM has many unique advantages, such as simple codes, easy implementation of boundary conditions, and fully parallelism. These features of LBM have attracted many scientists and engineers from various fields. Until now, the applications of LBM have achieved great success in multiphase flow, porous flow, suspension particle flow, magnetohydrodynamics, and biologically mechanics, etc. LBM has become an important method for computational fluid dynamics. However, there still exist some disadvantages in LBM, such as combustion simulation, treatment interactions between different phases on a non-uniform grid, the coupling in gas-solid flows. Little work has been done in these fields. In order to facilate the applications of LBM in our subject, I have conducted some related studies in this thesis. Firstly, we study the treatments of external force in LBM, and discuss their advantages/disadvantages. Owing to the resemblance between the treatment of external force and reactive source term in LBM, it is very important to understand how to handle the external force in LBM. But surprisingly, there is little work on this topic. Therefore, we will start our work from this issue. Second, we construct a lattice Boltzmann model to simulate gas-solid flows in the two-way coupling framwork. We do this by treating the gas phase and the particulate phase respectively, based on the divide and conquer principle in mathematics: the gas flow is modeled by LBM, while the particle motion is described by solving the Newton equation. This model is expected to have potential applications due to the advantages of the two-way coupling method, and the advantages of LBM is maintained completely in this model. In the third part, we propose a novel finite-difference Lattice Boltzmann Model with an external force. The heuristic method employed in this model can be extended to other LB model, such as the incompressible model using a pressure distribution function. Furthermore, we present the relationship between this finite Lattice Boltzmann Model and other models with an external force. Finally, we design a simple Lattice Boltzmann scheme for simulating low Mach number combustion. We get rid of the constraint in other Lattice Boltzmann Models, and firstly use a pure Lattice Boltzmann Model to simulate realistic combustion phenomena. Furthermore, this model has the same advantages as the standard Lattice Boltzmann models, such as good numerical efficiency, easy implementation on high performance parallel computers, without any additional limitations and computational costs. In addition, the model used here provides a new way for designing other Lattice Boltzmann models. We also discuss boundary treatment scheme of LBM because it will affect the numerical precision and stability. Although many studies have been done on this topic, most of them are only for isothermal flows. In our study, we find that boundary treatment schemes have an importanl influences in combustion simulation. In conclusion, this thesis has made some efforts to improve the applications of LBM in multiphase flows and reactive flows. Several new models are designed and some relevant problems are studied. In addition, various numerical tests are conducted to verify the performance of the models and methods. This work can serve as a base for the applications of LBM in our subject.更多还原