十三点格子Boltzmann模型仿真

格子气和格子Boltzmann方法的迅速发展提供了一类求解流体力学问题的新方法。格子Boltzmann方法在保留了格子气模型优点的同时,克服了它的不足之处。本文讨论了一种三迭加HPP十三点模型,通过选择适当的平衡分布及参数,并用Chapman－Enskog展开和多尺度技术导出了Navier－Stokes方程。在微机上模拟了空腔流的流动问题,并与传统方法的计算结果进行了比较,结果表明该模型能较好的模拟复杂流动现象,并具有较好的工程应用背景。     

Couette流和空腔粘性流的格子Boltzmann方法模拟

采用１３速六方格子Ｂｏｌｔｚｍａｎｎ方程研究Ｃｏｕｅｔｔｅ流和空腔粘性流,模拟了在Ｐｒ＝０．９１,Ｒｅ＝１００,５０００,及Ｐｒ＝０．９１,１,１．２５而Ｒｅ＝３０００情总下Ｃｏｕｅｔｔｅ流流场的速度、温度分布,研究了热输运过程;同时用该模型拟了高雷诺数的空腔粘性流流场演化稳定后,形成的涡旋的形状及腔内温度分布情况。     

三维十五点格子Boltzmann模型仿真

格子气和格子Ｂｏｌｔｚｍａｎｎ方法的迅速发展提供了一类求解流体力学问题的新方法。格子Ｂｏｌｔｚｍａｎｎ方法在保留了格子气模型优点的同时,克服了它的不足之处。本文讨论了一种三维十五点格子Ｂｏｌｔｚｍａｎｎ模型,通过选择适当的平衡分布及参数,并用Ｃｈａｐｍａｎ－Ｅｎｓｋｏｇ展开和多尺度技术导出了Ｎａｖｉｅｒ－Ｓｔｏｋｅｓ方程．在微机上模拟了工程中比较常见的管排绕流问题,并与实验观察到的结果进行了比较,结果表明该模型能较好的模拟复杂流动现象,并具有较好的工程应用背景。     

两相方腔流的格子Boltzmann模拟

利用基于Shan-Chen多相模型的格子Boltzmann方法对方腔内上板拖动的两相流动问题开展较为系统的数值模拟,详细研究雷诺数(Re),毛细数(Ca)和壁面润湿性对流动以及混合特性的影响.结果表明:Re数、Ca数越大,方腔内两相流体的混合界面长度越大,混合效果越好.另外,壁面憎水程度越高,混合界面长度增加越快,然而对于强亲水壁面,混合界面长度最终趋于一常数.     

二维空腔黏性流的格子Boltzmann方法模拟

用13速六方格子BhatnagarGrossKrook(缩写为BGK)模型模拟二维空腔黏性流.给出了上边界流体作匀速运动时,具有不同雷诺数的空腔黏性流的流场速度分布情况,模拟了在雷诺数Re=3000时,流场中的涡旋形成过程及流场稳定后,腔内密度、压力和温度的分布情况 关键词：     

格子Boltzmann方法对Rayleigh-Benard流的模拟与非线性分析

本文利用格子Boltzmann方法对不同Ra下的Rayleigh-Benard自然对流进行了数值模拟,得到的Nu与前人的结果一致。数值结果表明,Ra=2000时,格子Boltzmann方法得到了三个静态分岔解,其中一个为非稳定解;在Ra=5×10~5时格子Boltzmann方法得到了类似于周期的振荡解。本文采用插值格子Boltzmann方法,在Ra=2000,取不同插值节点进行计算时,得到了一种非稳态解。     

微尺度振荡Couette流的格子Boltzmann模拟

采用有效多松弛时间-格子Boltzmann方法(Effective MRT-LBM)数值模拟了微尺度条件下的振荡Couette和Poiseuille流动. 在微流动LBM中引入Knudsen边界层模型,对松弛时间进行修正. 模拟时平板或外力以正弦周期振动,Couette流中考虑了单平板振动、上下板同相振动这两类情况. 研究结果表明,修正后的MRT-LBM模型能有效用于这类非平衡的微尺度流动模拟;对于Couette流,随着Kn数的增大,壁面滑移效应变得越明显. St越大,板间速度剖面的非线性特性越剧烈;两板同相振荡时,若Kn,St均较小,板间流体受到平板拖动剪切的影响很小,板间速度几乎重叠在一起;在振荡Poiseuille流动中,St数增大到一定值时,相位滞后现象减弱;相对于Kn数,St数对振荡Couette 和Poiseuille流中不同位置处速度相位差的产生有较大影响. 关键词： 格子Boltzmann方法 有效MRT模型 Knudsen层 振荡流     

微多孔介质非牛顿流体格子Boltzmann模拟

根据修正Blake-Kozeny方程对Herschel-Bulkley模型的非牛顿流体在微多孔介质中流动的定量描述,通过增加外力项建立了非牛顿流体在宏观多孔介质中的格子Boltzmann模型,并将该模型应用到平板多孔介质中非牛顿流体的电渗驱动流模拟。对多孔介质渗透性参数和非牛顿流体流变性参数的影响进行模拟和分析,获得了各种参数对多孔介质中非牛顿流体流动速度的影响规律。     

用格子Boltzmann方法模拟MKDV方程

用精确到0(ε)的5速格子Boltzmann模型模拟MKDV方程:u_t+6u²u_x+u_xxx=0,并与MKDV方程的孤子解比较,二者精确吻合. 关键词： 格子Boltzmann方法 MKDV方程 孤子解     

用格子Boltzmann方法模拟高雷诺数下的热空腔黏性流

对13速六方格子Bhatnagar-Gross-Krook模型进行改进,适当地选取弛豫时间τ和k,使得热流体的切黏滞系数μ与热导系数λ只与内能有关,流体的Prandtl数可调.用该模型模拟了高雷诺数下的各种边界空腔流 关键词： 格子Boltzmann方法 Bhatnagar-Gross-Krook模型 Prandtl数 空腔流     

Simulation of Cardiac Flow under the Septal Defect Based on Lattice Boltzmann Method

In this paper, the lattice Boltzmann method was used to simulate the cardiac flow in children with aseptal defect. The inner wall model of the heart was reconstructed from 210 computed tomography scans. By simulating and comparing the cardiac flow field, the pressure field, the blood oxygen content, and the distribution of entropy generation before and after an operation, the effects of septal defect on pulmonary hypertension(PH), cyanosis, and heart load were analyzed in detail. It is found that the atrial septal defect(ASD) of the child we analyzed had a great influence on the blood oxygen content in the pulmonary artery, which leads to lower efficiency of oxygen binding in the lungs and increases the burden on the heart. At the same time, it also significantly enhanced the entropy generation rate of the cardiac flow, which also leads to a higher heart load. However, the main cause of PH is not ASD, but ventricular septal defect (VSD). Meanwhile, it significantly reduced the blood oxygen content in the brachiocephalic trunk, but rarely affects the blood oxygen contents in the downstream left common carotid artery, left subclavian artery, and descending aorta are not significantly affected by VSD. It causes severe cyanosis on the face and lips.     

用格子Boltzmann方法模拟壁面微结构对管流特性的影响

采用格子Boltzmann方法和Shan-Chen多相流模型,模拟液滴在常力驱动下在微管道内的流动,研究微孔道壁面润湿性和几何结构对降压增注效果的影响.阐明具有一定粗糙度的疏水表面阻力减小的原因,研究表明,壁面润湿性和粗糙度对管流特性有显著的影响,同时也表明,用Lattice Boltzmann方法模拟,具有相当精确的可预测性,在石油储层微观渗流减阻机制研究方面有很好的应用前景,其可为研究纳米降压增注效果提供有用工具.     

微通道内气体流动的格子Boltzmann方法研究

采用格子Boltzmann方法模拟了微通道在滑移区内不同Knudsen数下的微气体Poiseuille流,分析了微气体流动的速度分布以及流量与压降的关系,并给出了相对滑移长度和Poiseuille数随Knudsen数的变化特性。研究结果表明,微气体Poiseuille流的速度轮廓呈抛物线分布,但是边界速度大于0,出现速...     

Aeroacoustic Simulations Using Compressible Lattice Boltzmann Method

This paper presents a lattice Boltzmann (LB) method based study aimed at numerical simulation of aeroacoustic phenomenon in flows around a symmetric obstacle. To simulate the compressible flow accurately, a potential energy double-distribution-function (DDF) lattice Boltzmann method is used over the entire computational domain from the near to far fields. The buffer zone and absorbing boundary condition is employed to eliminate the non-physical reflecting. Through the direct numerical simulation, the flow around a circular cylinder at $Re$=150, $M$=0.2 and the flow around a NACA0012 airfoil at $Re$=10000, $M$=0.8, $α$=$0^◦$ are investigated. The generation and propagation of the sound produced by the vortex shedding are reappeared clearly. The obtained results increase our understanding of the characteristic features of the aeroacoustic sound.     

A Hybrid Lattice Boltzmann Flux Solver for Simulation of Viscous Compressible Flows

In this paper, a hybrid lattice Boltzmann flux solver (LBFS) is proposed for simulation of viscous compressible flows. In the solver, the finite volume method is applied to solve the Navier-Stokes equations. Different from conventional Navier-Stokes solvers, in this work, the inviscid flux across the cell interface is evaluated by local reconstruction of solution using one-dimensional lattice Boltzmann model, while the viscous flux is still approximated by conventional smooth function approximation. The present work overcomes the two major drawbacks of existing LBFS [28–31], which is used for simulation of inviscid flows. The first one is its ability to simulate viscous flows by including evaluation of viscous flux. The second one is its ability to effectively capture both strong shock waves and thin boundary layers through introduction of a switch function for evaluation of inviscid flux, which takes a value close to zero in the boundary layer and one around the strong shock wave. Numerical experiments demonstrate that the present solver can accurately and effectively simulate hypersonic viscous flows.     

Simulation of Combustion Field with Lattice Boltzmann Method

Turbulent combustion is ubiquitously used in practical combustion devices. However, even chemically non-reacting turbulent flows are complex phenomena, and chemical reactions make the problem even more complicated. Due to the limitation of the computational costs, conventional numerical methods are impractical in carrying out direct 3D numerical simulations at high Reynolds numbers with detailed chemistry. Recently, the lattice Boltzmann method has emerged as an efficient alternative for numerical simulation of complex flows. Compared with conventional methods, the lattice Boltzmann scheme is simple and easy for parallel computing. In this study, we present a lattice Boltzmann model for simulation of combustion, which includes reaction, diffusion, and convection. We assume the chemical reaction does not affect the flow field. Flow, temperature, and concentration fields are decoupled and solved separately. As a preliminary simulation, we study the so-called counter-flow laminar flame. The particular flow geometry has two opposed uniform combustible jets which form a stagnation flow. The results are compared with those obtained from solving Navier–Stokes equations.     

Lattice Boltzmann Model for Free Surface Flow for Modeling Foaming

We present a 2D- and 3D-lattice Boltzmann model for the treatment of free surface flows including gas diffusion. Interface advection and related boundary conditions are based on the idea of the lattice Boltzmann equation. The fluid dynamic boundary conditions are approximated by using the mass and momentum fluxes across the interface, which do not require explicit calculation of gradients. A similar procedure is applied to fulfill the diffusion boundary condition. Simple verification tests demonstrate the correctness of the algorithms. 2D- and 3D-foam evolution examples demonstrate the potential of the method.     

方腔内微细颗粒物运动特性的格子Boltzmann方法模拟

对Masselot and Chopard提出的模拟气固两相流动的格子Boltzmann-格子气(LBE-LGA)方法进行推广,能够反映两相间拖曳作用.利用该方法研究封闭方腔内的气固两相流运动特性,分析斯托克斯数St和模拟颗粒数目对颗粒群运动的影响,并与文献结果进行比较,表明LBE-LGA方法模拟颗粒运动是可行的.     

多孔介质内交变流动与换热的格子Boltzmann研究

针对制约脉冲管制冷机效率提高的蓄冷器内交变流动与换热问题,本文使用格子Boltzmann方法计算并分析了多孔介质内交变流动与换热特性。结果表明,交变流动压力波振幅对速度与压力和温度间的相位差的影响很小;通道界面处速度与压力的相位差在某一孔隙率下有一极小值;多孔介质内最大阻力系数与雷诺数的关系可以为设计蓄冷器时填料结构的...