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用九速正方格子模型给出了二维对流扩散方程的格子Boltzmann方法。由对流扩散方程的对流系数和扩散系数确定了局域平衡分布函数的系数。计算机模拟结果与理论结果吻合很好。 相似文献
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研究了温盐双扩散系统的多组分格子Boltzmann方法.通过对二维方腔的温盐双扩散系统的数值模拟,检验了方法的可行性及有效性,所得到的结果与差分法结果符合良好,继而将此方法推广到三维,建立了三维温盐双扩散系统的格子Boltzmann方法,对三维方腔双扩散问题进行了模拟和分析,并与差分法模拟的结果进行了比较,结果令人满意.最后,分析了格子Boltzmann方法在模拟双扩散对流问题时存在的局限性.
关键词:
格子Boltzmann方法
温盐双扩散
Boussinesq近似
数值模拟 相似文献
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在通过引入精确差分方法的单组分多相格子Boltzmann模型的基础上耦合能量方程,并考虑流体与固壁间的相互作用力来调节气泡与固壁间的接触角,从而建立了一种新的描述气液相变的格子Boltzmann理论模型. 为验证该模型的正确性,利用其对工质为水的相变过程进行了模拟,发现模拟结果与实验值符合良好;进而利用其验证Laplace定律,发现计算所得的水的表面张力与实验值甚为符合. 为考察该模型处理复杂相变问题的能力,利用其对工质为水的池沸腾中的气泡生长过程进行模拟,发现气泡脱离直径与g-0
关键词:
格子Boltzmann方法
池沸腾
气泡生长过程
接触角 相似文献
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建立自然对流作用下融化的格子Boltzmann双分布函数模型,根据非线性对流扩散方程的格子Boltzmann模型理论提出一个新的表征融化温度场的分布函数演化方程,并通过变松弛时间方法处理固液两相变热物性传热问题.应用模型对热传导融化及自然对流融化特别固液变热物的融化过程进行模拟.模拟结果与分析解、经典的关联式结果吻合较好,模型的正确性得到了验证.模拟结果表明,自然对流对融化传热过程有着重要的影响,此外固相热传导也对融化传热、融化速率及固液两相温度分布都有一定影响. 相似文献
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基于D1Q4可压缩格子Boltzmann模型,按照流通矢量分裂方法的思路,采用坐标旋转技术构造求解三维带化学反应Navier-Stokes方程对流通量求解器.结合有限体积法求解三维化学非平衡流Navier-Stokes方程,采用时间算子分裂算法解决化学反应刚性问题,数值模拟超声速化学非平衡流的三个经典算例.数值结果表明:在高马赫数下,采用D1Q4可压缩格子Boltzmann模型构造的三维对流通量求解器数值模拟中没有出现非物理解,同时在超声速化学非平衡流场中正确分辨激波、燃烧波等物理现象,精度和分辨率均较高,验证了本文构造的三维对流通量求解器的可靠性,拓宽了D1Q4可压缩格子Boltzmann模型的应用范围,为计算超声速化学非平衡流提供一种新方法. 相似文献
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Lack of energy conservation in lattice Boltzmann models leads to unrealistically high values of the bulk viscosity. For this reason, the lattice Boltzmann method remains a computational tool rather than a model of a fluid. A novel lattice Boltzmann model with energy conservation is derived from Boltzmann's kinetic theory. Simulations demonstrate that the new lattice Boltzmann model is the valid approximation of the Boltzmann equation for weakly compressible flows and microflows. 相似文献
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The classical Chapman–Enskog expansion is performed for the recently proposed finite-volume formulation of lattice Boltzmann equation (LBE) method [D.V. Patil, K.N. Lakshmisha, Finite volume TVD formulation of lattice Boltzmann simulation on unstructured mesh, J. Comput. Phys. 228 (2009) 5262–5279]. First, a modified partial differential equation is derived from a numerical approximation of the discrete Boltzmann equation. Then, the multi-scale, small parameter expansion is followed to recover the continuity and the Navier–Stokes (NS) equations with additional error terms. The expression for apparent value of the kinematic viscosity is derived for finite-volume formulation under certain assumptions. The attenuation of a shear wave, Taylor–Green vortex flow and driven channel flow are studied to analyze the apparent viscosity relation. 相似文献
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提出了用于正则长波方程的5-Bit格子Boltzmann模型。应用Chapman-Enskog展开和多重尺度技术,通过选择平衡态分布函数的高阶矩,得到了时间尺度t0上的守恒律,从而给出三阶精度的算法。模型中的参数通过稳定性分析给出。 相似文献
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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
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Lattice Boltzmann Simulation of Free-Surface Temperature Dispersion in Shallow Water Flows 下载免费PDF全文
Mohammed Seaï d & Guido Thö mmes 《advances in applied mathematics and mechanics.》2009,1(3):415-437
We develop a lattice Boltzmann method for modeling free-surface
temperature dispersion in the shallow water flows. The governing
equations are derived from the incompressible Navier-Stokes
equations with assumptions of shallow water flows including bed
frictions, eddy viscosity, wind shear stresses and Coriolis forces.
The thermal effects are incorporated in the momentum equation by
using a Boussinesq approximation. The dispersion of free-surface
temperature is modelled by an advection-diffusion equation. Two
distribution functions are used in the lattice Boltzmann method to
recover the flow and temperature variables using the same lattice
structure. Neither upwind discretization procedures nor Riemann
problem solvers are needed in discretizing the shallow water
equations. In addition, the source terms are straightforwardly
included in the model without relying on well-balanced techniques to
treat flux gradients and source terms. We validate the model for a
class of problems with known analytical solutions and we also
present numerical results for sea-surface temperature distribution
in the Strait of Gibraltar. 相似文献
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多孔介质中高Péclet数和大黏性比下混溶流体的流动和扩散广泛存在于二氧化碳驱油、化工生产等工业过程中.用数值方法对该问题进行研究时,关键在于如何正确描述高Péclet数和大黏性比下多孔介质内流体的行为.为此,提出了一种基于多松弛模型和格子动理模型的耦合格子Boltzmann模型.通过Chapman-Enskog分析,证明该模型能有效求解不可压Navier-Stokes方程和对流扩散方程.数值结果表明,该模型不仅具有二阶精度和良好的稳健性,而且对于高Péclet数和大黏性比的问题具有良好的数值稳定性,为模拟此类问题提供了有效工具. 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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Dirk Kehrwald 《Journal of statistical physics》2005,121(1-2):223-237
It is shown how shear-thinning flow can be simulated without the need for numerical differentiation by following a lattice
Boltzmann approach. The basic idea of is to combine the Cross model of viscosity with a 3D multiple relaxation time lattice
Boltzmann method and to extract the required velocity derivatives from intrinsic quantities of the lattice Boltzmann scheme.
Computational results are presented for a simple benchmark and for the simulation of liquid composite moulding. 相似文献