共查询到19条相似文献,搜索用时 312 毫秒
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根据微观和宏观之间的质量、动量、能量守恒准则和在原格子Boltzmann模型基础上,建立了几个新的格子Boltzmann模型,使得在外力场中的格子Boltzmann模型得到进一步完善.通过还原宏观流体力学方程,捕捉到了浮力强迫系数与Grashof数之间的关系.所得动量方程和Navier Stokes方程相比,在黏性输运项上有明显的改进,说明黏性应力不但与流体的速度梯度和流体的压缩性有关,而且还与非定常的内能梯度和动量通量有关.该模型对非等温流场的数值结果证明了其具有很好的数值稳定性和适用性.
关键词:
Boltzmann模型
平衡分布函数
流体力学方程 相似文献
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格子Boltzmann方法的质量扩散模型 总被引:5,自引:2,他引:3
建立了多组份流体、多速度格子Boltzmann模型。该模型满足流体质量扩散方程和运动方程。通过正弦波的衰减过程测量了两流体间的扩散系数。对圆形区域内的静止流体在具有均匀来流速度的另外一种流体中的对流扩散问题进行了数值模拟。 相似文献
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采用格子Boltzmann方法研究了孔隙尺度下多孔介质内含流固溶解反应的互溶驱替过程,重点研究了被驱替流体与驱替流体黏性差异较大的情况下,溶解反应引起的多孔介质内部结构变化对驱替过程的影响;定量分析了不同达姆科勒数及佩克莱数下多孔介质孔隙率和驱替过程驱替效率随时间的演变.研究结果表明:达姆科勒数较大时,溶解反应的发生会在多孔介质内部生成虫洞,导致一部分被驱替流体不能被波及,驱替流体沿虫洞离开多孔介质,造成驱替效率的减少.在此基础上,随着达姆科勒数的增大,孔隙率变化越大,生成的虫洞越宽,最终驱替效率变大,但仍小于无溶解反应时的驱替效率;随着佩克莱数的增大,指进增长速度越快,孔隙率变化越小,驱替效率越小. 相似文献
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《物理学报》2016,(23)
为了研究孔隙水含少量气泡时多孔介质中波的传播,本文在Biot模型的基础上,将孔隙水中气泡的体积振动融合到多孔介质的孔隙流体渗流连续性方程中,从而得到了考虑气泡体积振动的孔隙流体渗流连续性方程.在此基础上,根据气泡线性振动下气泡瞬时半径和介质背景压力的关系,以及多孔介质运动方程和流体介质运动方程,导出了受气泡影响下多孔介质位移矢量波动方程,建立了非水饱和多孔介质声速频散和衰减预报模型.气泡的存在增大了孔隙水的压缩率,导致含气泡水饱和多孔介质声速的降低.当声波频率等于气泡的共振频率时,在声波激励下,介质呈现高频散,且孔隙水中的气泡产生共振,吸收截面达到最大,使得多孔介质的声衰减也达到最大.文中数值分析验证了上述结论,表明了气泡含量、大小和驱动声场频率是影响声波在含少量气泡的水饱和多孔介质中传播的主要因素. 相似文献
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During the past two decades, the lattice Boltzmann (LB) method has been introduced as a class of computational fluid dynamic methods for fluid flow simulations. In this method, instead of solving the Navier Stocks equation, the Boltzmann equation is solved to simulate the flow of a fluid. This method was originally developed based on uniform grids. However, in order to model complex geometries such as porous media, it can be very slow in comparison with other techniques such as finite differences and finite elements. To eliminate this limitation, a number of studies have aimed to formulate the lattice Boltzmann on the unstructured grids. This paper deals with simulating fluid flow through a synthetic porous medium using the LB method and on the quadtree grid structure. To this end, the LB method was used on nonuniform grids coupled with a technique for image reconstruction which resulted in the quadtree grids for simulation of fluid flow through porous media. Accuracy and efficiency of this algorithm is compared against the conventional LB method based on uniform grids. While the decrease in computational time in the proposed LB method on nonuniform grids is found to be significant regarding the size of the initial and reconstructed images, the same level of accuracy is obtained when compared with the conventional LB method on uniform grids. 相似文献
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根据格子Boltzmann方法及相关理论,建立了一个新的模拟渗流运动的数值模型,所得模型没有在边界上采取相应平均措施,同时还避免了一些非物理副产品的出现-实例计算数值结果与精确解符合较好,证明模型可靠-
关键词:
渗流
格子Boltzmann方法
数值模型 相似文献
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Improving the Stability of the Multiple-Relaxation-Time Lattice Boltzmann Method by a Viscosity Counteracting Approach 下载免费PDF全文
Chunze Zhang Yongguang Cheng Shan Huang & Jiayang Wu 《advances in applied mathematics and mechanics.》2016,8(1):37-51
Numerical instability may occur when simulating high Reynolds number
flows by the lattice Boltzmann method (LBM). The multiple-relaxation-time (MRT)
model of the LBM can improve the accuracy and stability, but is still subject to numerical
instability when simulating flows with large single-grid Reynolds number
(Reynolds number/grid number). The viscosity counteracting approach proposed recently
is a method of enhancing the stability of the LBM. However, its effectiveness
was only verified in the single-relaxation-time model of the LBM (SRT-LBM). This paper
aims to propose the viscosity counteracting approach for the multiple-relaxation-time
model (MRT-LBM) and analyze its numerical characteristics. The verification is
conducted by simulating some benchmark cases: the two-dimensional (2D) lid-driven
cavity flow, Poiseuille flow, Taylor-Green vortex flow and Couette flow, and three-dimensional
(3D) rectangular jet. Qualitative and Quantitative comparisons show that
the viscosity counteracting approach for the MRT-LBM has better accuracy and stability
than that for the SRT-LBM. 相似文献
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A lattice Boltzmann model for simulating fluids with multiple components and interparticle forces proposed by Shan and Chen is described in detail. Macroscopic equations governing the motion of each component are derived by using the Chapman-Enskog method. The mutual diffusivity in a binary mixture is calculated analytically and confirment by numerical simulation. The diffusivity is generally a function of the concentrations of the two components but independent of the fluid velocity, so that the diffusion is Galilean invariant. The analytically calculated shear kinematic viscosity of this model is also confiremoed numerically. 相似文献
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Boundary scheme for lattice Boltzmann modeling of micro-scale gas flow in organic-rich pores considering surface diffusion 下载免费PDF全文
《中国物理 B》2019,(3)
We propose a boundary scheme for addressing multi-mechanism flow in a porous medium in slip and early transition flow regimes, which is frequently encountered in shale gas reservoirs. Micro-gaseous flow in organic-rich shale involves a complex flow mechanism. A self-developed boundary scheme that combines the non-equilibrium extrapolation scheme and the combined diffusive reflection and bounce-back scheme(half-way DBB) to embed the Langmuir slip boundary into the single-relaxation-time lattice Boltzmann method(SRT-LBM) enables us to describe this process, namely, the coupling effect of micro-gaseous flow and surface diffusion in organic-rich nanoscale pores. The present LBM model comes with the careful consideration of the local Knudsen number, local pressure gradient, viscosity correction model, and regularization procedure to account for the rarefied gas flows in irregular pores. Its validity and accuracy are verified by several benchmarking cases, and the calculated results by this boundary scheme accord well with our analytical solutions.This boundary scheme shows a higher accuracy than the existing studies. Additionally, a subiteration strategy is presented to tackle the coupled micro-gaseous flow and surface diffusion, which necessitates the iteration process matching of these two mechanisms. The multi-mechanism flow in the self-developed irregular pores is also numerically investigated and analyzed over a wide range of parameters. The results indicate that the present model can effectively capture the coupling effect of micro-gaseous flow and surface diffusion in a tree-like porous medium. 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