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1.
In recent years, the lattice Boltzmann method (LBM) has been widely adopted to simulate various fluid systems, and the boundary treatment has been an active topic during the LBM development. In this paper, we present a novel approach to improve the bounce-back boundary treatment for moving surfaces with arbitrary configurations. We follow the framework originally proposed by Ladd [A.J.C. Ladd, Numerical simulations of particulate suspensions via a discretized Boltzman equation. Part 1. Theoretical foundation, Journal of Fluid Mechanics 271 (1994) 285–309]; however, the adjustment in the density distribution during the bouncing-back process at the boundary is calculated using the midpoint velocity inter-/extrapolated from the boundary and fluid velocities, instead of the real boundary velocity in the Ladd method. This modification ensures that the bouncing-back process and the density distribution adjustment both take place at a same location: the midpoint of a boundary lattice link, and thus removes the discrepancy of bouncing-back at the midpoint but density distribution adjustment at the boundary point in the original Ladd method. When compared with other existing boundary models, this method involves a simpler algorithm and exhibits a comparable or even better accuracy in describing flow field and flow-structure interaction, as demonstrated by several test simulations. Therefore, this boundary method could be considered as a competitive alternative for boundary treatment in LBM simulations, especially for particulate and porous flows with large fluid–solid interfacial areas. 相似文献
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《Physics letters. A》2006,354(3):173-182
A momentum exchange-based immersed boundary-lattice Boltzmann method is presented in this Letter for simulating incompressible viscous flows. This method combines the good features of the lattice Boltzmann method (LBM) and the immersed boundary method (IBM) by using two unrelated computational meshes, an Eulerian mesh for the flow domain and a Lagrangian mesh for the solid boundaries in the flow. In this method, the non-slip boundary condition is enforced by introducing a forcing term into the lattice Boltzmann equation (LBE). Unlike the conventional IBM using the penalty method with a user-defined parameter or the direct forcing scheme based on the Navier–Stokes (NS) equations, the forcing term is simply calculated by the momentum exchange of the boundary particle density distribution functions, which are interpolated by the Lagrangian polynomials from the underlying Eulerian mesh. Numerical examples show that the present method can provide very accurate numerical results. 相似文献
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浸入边界—晶格波尔兹曼法在流固耦合等复杂的流体系统中得到广泛的应用.本文采用基于速度源修正的浸入边界—晶格玻尔兹曼法,建立了仿生微流体驱动模型,创新性地将波动弹性体的速度引入晶格玻尔兹曼方程,避免了传统浸入边界—晶格玻尔兹曼法中浸入边界速度-结构变形-力之间的转换,提高了计算效率和准确率.研究了行波波动细丝对流场内流动速度和压力的影响,重点分析了驱动模型各项参数对微流体的驱动效果.研究结果表明:细丝长度、频率、振幅的增加引起出口处流量的增加;波长、流体粘滞系数以及细丝位置与出口处流量呈复杂的非线性关系. 相似文献
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采用格子Boltzmann方法(LBM)建立了气液固三相耦合的动力学模型,研究了相同尺度下上浮气泡与复杂壁面的相互耦合作用.首先,基于黏性流体理论,通过构建一组格子Boltzmann(LB)方程来描述气液两相的运动,并以LB离散体积力的形式计入了黏性力、表面张力和重力.同时,采用LBM中的Half-way反弹模型与有限差分格式相结合的方式进行固壁边界的处理.然后,利用本文建立的模型,对不同特征尺寸比条件下,气泡与考虑边缘效应的平面固壁和曲面固壁的耦合特性进行了研究.研究发现固壁边界条件以及特征尺寸比对气泡的运动和拓扑结构的变化都具有明显的非线性影响.最后,研究了流体属性对气泡与复杂壁面耦合规律的影响. 相似文献
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格子Boltzmann方法伪势多相模型具有高效性和复杂几何边界实施的简易性。该文采用改进作用力的伪势多相模型,通过优化参数实现最大程度的热力学一致性,进而提高模型的密度比和稳定性。分别从伪速度、网格不变性、Young-Laplace验证等方面研究了改进模型的性能。通过改进的模型模拟了复杂几何固壁附近空泡溃灭过程。分析了空化泡溃灭阶段的密度场、压力场和速度场演化过程,以及复杂几何固壁附近的空泡动力学特性。结果表明伪势格子Boltzmann方法在探索空泡溃灭和复杂几何固壁间的相互作用规律研究中是一种有效的工具。 相似文献
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We integrate the lattice Boltzmann method (LBM) and immersed boundary method (IBM) to capture the coupling between a rigid boundary surface and the hydrodynamic response of an enclosed particle laden fluid. We focus on a rigid box filled with a Newtonian fluid where the drag force based on the slip velocity at the wall and settling particles induces the interaction. We impose an external harmonic oscillation on the system boundary and found interesting results in the sedimentation behavior. Our results reveal that the sedimentation and particle locations are sensitive to the boundary walls oscillation amplitude and the subsequent changes on the enclosed flow field. Two different particle distribution analyses were performed and showed the presence of an agglomerate structure of particles. Despite the increase in the amplitude of wall motion, the turbulence level of the flow field and distribution of particles are found to be less in quantity compared to the stationary walls. The integrated LBM-IBM methodology promised the prospect of an efficient and accurate dynamic coupling between a non-compliant bounding surface and flow field in a wide-range of systems. Understanding the dynamics of the fluid-filled box can be particularly important in a simulation of particle deposition within biological systems and other engineering applications. 相似文献
9.
Non—equilibrium extrapolation method for velocity and pressure boundary conditions in the lattice Boltzmann method 总被引:35,自引:0,他引:35
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In this paper, we propose a new approach to implementing boundary conditions in the lattice Boltzmann method (LBM). The basic idea is to decompose the distribution function at the boundary node into its equilibrium and non-equilibrium parts, and then to approximate the non-equilibrium part with a first-order extrapolation of the non-equilibrium part of the distribution at the neighbouring fluid node. Schemes for velocity and pressure boundary conditions are constructed based on this method. The resulting schemes are of second-order accuracy. Numerical tests show that the numerical solutions of the LBM together with the present boundary schemes are in excellent agreement with the analytical solutions. Second-order convergence is also verified from the results. It is also found that the numerical stability of the present schemes is much better than that of the original extrapolation schemes proposed by Chen et al. (1996 Phys. Fluids 8 2527). 相似文献
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The lattice Boltzmann cellular automaton method has been successfully extended for analysis of fluid interactions with a deformable membrane or web. The hydrodynamic forces on the solid web are obtained through computation of the fluid flow stress at the moving boundary using the lattice Boltzmann method. Analysis of solid boundary deformation or vibration due to hydrodynamic force is based on Newtonian dynamics and a molecular dynamic type approach. 相似文献
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In this paper we address the problem of the time evolution of a perturbation around a steady base flow with the use of the lattice Boltzmann method (LBM). This approach, named base flow lattice Boltzmann method, is of great interest in particular for aeroacoustic fields where the acoustic perturbation, on the one hand, is almost exclusively influenced by the large scale average structures of the underlying flow, and on the other hand, has a low effect on the large structures. The method is implemented for weakly compressible flows and the results of the base flow lattice Boltzmann are compared with the standard single relaxation time LBM. The boundary conditions for the base flow lattice Boltzmann method are discussed, as well as the implementation of outflow conditions for acoustic waves. 相似文献
13.
Changsheng Huang Baochang Shi Nanzhong He & Zhenhua Chai 《advances in applied mathematics and mechanics.》2015,7(1):1-12
The lattice Boltzmann method (LBM) can gain a great amount of
performance benefit by taking advantage of graphics processing unit
(GPU) computing, and thus, the GPU, or multi-GPU based LBM can be
considered as a promising and competent candidate in the study of
large-scale fluid flows. However, the multi-GPU based lattice
Boltzmann algorithm has not been studied extensively, especially for
simulations of flow in complex geometries. In this paper, through
coupling with the message passing interface (MPI) technique, we
present an implementation of multi-GPU based LBM for fluid flow
through porous media as well as some optimization strategies based
on the data structure and layout, which can apparently reduce memory
access and completely hide the communication time consumption. Then
the performance of the algorithm is tested on a one-node cluster
equipped with four Tesla C1060 GPU cards where up to 1732 MFLUPS is
achieved for the Poiseuille flow and a nearly linear speedup with
the number of GPUs is also observed. 相似文献
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本文采用格子Boltzmann方法模拟了多孔介质内的溶解和沉淀现象, 并分析了雷诺数、施密特数、达姆科勒数对多孔介质孔隙结构及浓度分布的影响. 结果表明: 对于多孔介质内的溶解(沉淀)过程, 当雷诺数越大时, 孔隙率越大(小), 平均浓度值越小(大); 当达姆科勒数或施密特数较小时, 溶解和沉淀过程均受反应控制, 此时反应在多孔介质的固体表面较为均匀的发生; 当达姆科勒数或施密特数较大时, 溶解和沉淀过程均受扩散控制, 此时反应主要发生在上游及大孔隙区域. 相似文献
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This paper presents a heuristic optimality criterion algorithm for shape design of fluid flow. In this algorithm, the lattice Boltzmann method (LBM) is utilized to calculate the flow field of a fluid domain which is divided into elemental cells. A heuristic optimality criterion is applied for cells at the solid–fluid interface, i.e. the dynamic pressure for fluid cells and the viscous stress on their neighboring solid cells. An automatic program is processed step by step to exchange the positions of solid and fluid cells identified by the optimality criterion, with the objective of decreasing the flow resistance at the constraint of constant fluid volume. To illustrate the procedure of this algorithm for shape design of fluid flow, two simple examples are presented: one with fluid flowing through a right angle elbow and the other through a converging T-junction. Numerical results show that this algorithm can successfully reduce the total pressure drop of the system, demonstrating its potential applications in engineering optimal design. 相似文献
18.
Fluid-Structure Interaction in Microchannel Using Lattice Boltzmann Method and Size-Dependent Beam Element
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V. Esfahanian E. Dehdashti & A. M. Dehrouyeh-Semnani 《advances in applied mathematics and mechanics.》2014,6(3):345-358
Fluid-structure interaction (FSI) problems in microchannels play prominent roles in many
engineering applications. The present study is an effort towards the simulation of flow
in microchannel considering FSI. Top boundary of the microchannel is assumed to be rigid
and the bottom boundary, which is modeled as a Bernoulli-Euler beam, is simulated by
size-dependent beam elements for finite element method (FEM) based on a modified couple
stress theory. The lattice Boltzmann method (LBM) using D2Q13 LB model is coupled to the
FEM in order to solve fluid part of FSI problem. In the present study, the governing
equations are non-dimensionalized and the set of dimensionless groups is exhibited to
show their effects on micro-beam displacement. The numerical results show that the
displacements of the micro-beam predicted by the size-dependent beam element are
smaller than those by the classical beam element. 相似文献
19.
高强度聚焦超声(HIFU)是一种新型的无创治疗肿瘤新技术,其中换能器声场数值计算能够为HIFU治疗提供重要的依据。传统非线性KZK和SBE模型广泛应用于换能器声场数值计算,但依然存在某些不足。我们采用一种介观尺度的新型流体力学方法,即格子Boltzmann方法(LBM),基于2维9离散速度(D2Q9)格子构建了轴对称多弛豫参数LBM模型,并通过调节弛豫参数分析其对模型的影响;利用该模型对两个具有不同张角的球面聚焦换能器的声场进行数值模拟,并与KZK和SBE模型的计算结果进行比较。结果表明LBM模型能够很好地描述超声波的激发和传播机制,从流体力学的角度描述聚焦声场的分布,具有清晰的物理意义,且计算过程不受换能器张角的限制,在换能器声场的理论分析和模拟计算及其在HIFU治疗中的应用有着积极的意义。 相似文献
20.
The effect of viscosity and viscosity difference and boundary patterned slip on mixing in a micro mixer has been numerically studied using lattice Boltzmann method (LBM). The slip and no-slip ratio is not constant and varies irregularly, and viscosity is altered by changing the relaxation time in LBE equation. The slip boundary condition is simulated by specular reflection boundary and the no-slip boundary condition is simulated by bounce back boundary. It has been found that it is feasible to optimize the micro mixer design by combining the viscosity effect and boundary patterned ratio altogether. 相似文献