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双语推荐：格子玻尔兹曼方法

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为将格子玻尔兹曼方法（LBM ）用于土木工程结构的气动弹性计算，提出了一种基于浸没边界‐格子玻尔兹曼（IB‐L B ）方法的流固耦合算法。该算法在多松弛时间格式的格子玻尔兹曼框架下构造大涡模拟作为流场求解器；采用龙格‐库塔法求解结构运动方程。为满足流固耦合面的无滑移性并提高算法的计算精度，采用一种迭代格式的浸没边界实施流固耦合面的数据交换。基于流固耦合算法编制分析程序对矩形断面的横向风振和福斯桥的颤振等气动弹性问题进行了模拟。与现有试验及数值结论的对比分析表明：本文算法可以较准确地预测矩形断面的涡振锁定风速、驰振临界风速及福斯桥的颤振临界风速。
In order to apply lattice Boltzmann method (LBM ) to aeroelastic analyses of the civil struc‐tures ,a fluid‐structure interaction (FSI ) algorithm based on immersed boundary‐lattice Boltzmann (IB‐LB) method w as presented in this paper. In the present algorithm ,large eddy simulation w as de‐veloped within the framework of multiple relaxation time lattice Boltzmann method to model the flow past the bluff body ,and the Runge‐Kutta method was used to solve the structural motion equations. In addition ,an implicit IB method was adopted to implement the fluid‐structure interface to satisfy the no‐slip condition and improve the accuracy of the FSI algorithm. The aeroelastic simulations of a rec‐tangular cylinder and the Forth Road Bridge were performed using self‐developed codes. The results show that the lock‐in phenomenon of vortex‐induced vibration and the critical galloping velocity cap‐tured by the present algorithm for the rectangular cylinder are in good agreem

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将大涡模拟（Large Eddy Simulation ，LES）和多弛豫时间格子玻尔兹曼（Multiple Relaxation Time（MRT） LBM ）方法相结合，用于解决LBM方法在高雷诺数流动模拟产生的数值不稳定的问题。结合D2Q9-M RT 模型与Smargorinsky涡粘模型，对高雷诺数下二维圆柱绕流进行数值模拟。并根据实验结果，系统分析了圆柱绕流涡的脱落形态，以及Strouhal数和其阻力升力系数随雷诺数的变化情况。实验结果表明该方法可以很好增加LBM在高雷诺数模拟中数值稳定性。
In this paper ,large-eddy simulation combined with multi-relaxation time lattice Boltzmann (MRT-LBM ) method is proposed for solving the poor stability problem in high Reynolds number flow simulation with LBM .The implementation is discussed in the context of 9-velocity (D2Q9 ) MRT-LBM model in conjunction with the Smargorinsky subgrid closure model .This model is used for doing the two-dimensional numerical simulation of flow around a cylinder with a high Reynolds number .According to the experimental results ,a systematic analysis of the form of shed vortex of flow around cylinder is made , and the variation of the Strouhal number and the drag coefficient with the change of Reynolds number .The experimental results show that the method can well increase numerical stability in the simulation with LBM in a high Reynolds number .

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用一种非简谐晶格动力学方法,使用相互作用势作为惟一的输入参数,准确地计算了固体氩的各个声子的频率和弛豫时间.并将这些结果进一步和玻尔兹曼输运方程相结合,预测了固体氩从10 K到80 K区间的热导率,并得到了与实验值非常符合的结果.分析了运用非简谐晶格动力学方法进行数值计算过程中的各个相关的计算参数,包括布里渊区中倒格子矢量的选取,δ函数的展宽的选择等对热导率和声子弛豫时间预测结果的影响.通过对各个声子模式对热导率贡献的分析,发现随着温度升高,高频声子对于热导率的贡献率也逐渐变大,结果和理论预测完全一致.
Anharmonic lattice dynamics method is employed to investigate the phonon frequency and relaxation time without any fitting parameters. The phonon relaxation time is used in Boltzmann transport equation to predict the lattice thermal conductivity of solid argon between 10 K and 80 K, and the results agree very well with experimental data. The effects of calculation parameters on the prediction accuracy are also analyzed, including mesh size of the reciprocal lattice points, and the broadening factor of delta function. The contribution of each individual phonon mode to the thermal conductivity is investigated. It is found that higher frequency phonons contribute more to the thermal conductivity at higher temperature, which is consistent with previous theoretical results.

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为研究岩石颗粒胶结方式对储层岩石弹性和渗流性质的影响,采用过程模拟法构建了三维数字岩心,在此基础上,分别利用有限元方法和格子玻尔兹曼方法研究了胶结物均匀生长、沿孔隙生长和沿喉道生长3种胶结方式对岩石弹性和渗流特性的影响规律.结果表明:岩石颗粒胶结方式会影响岩石刚性和孔隙连通性,引起岩石弹性模量和渗透率的变化.在相同孔隙度下,胶结物沿喉道生长形成的岩石抗压性最强,渗透率最小;沿孔隙生长形成的岩石抗压性最弱,渗透率最大.3种胶结方式下,岩石弹性模量随着胶结物含量增加而增大,变化率近似相等;岩石渗透率随着胶结物含量的增加而减小,岩石渗透性对颗粒胶结方式的变化更敏感.
In order to investigate the effects of cementation on elastic properties and permeability of reservoir rocks,a 3D digital model of core was constructed.Then this model was simulated using the process-based method and finite element lattice Boltz-mann method.The results show that cementation influences the rock stiffness and pore connectivity,controlling elastic modu-lus and rock permeability,respectively.Given same porosity,rocks with cement occurring in the pore throats have high elastic modulus and low permeability;whereas rocks with cement precipitating within pores have low elastic modulus and high permea-bility.Among the simulated three cementation scenarios,the rock elastic modulus increases with increasing amount of cement, and there is a linear relationship between them.Rock permeability,however,deceases with increasing amount of cement,be-cause permeability is more sensitive to where cements precipitate than rock elastic parameters.

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建立了二维双组分两相流的大密度比格子玻尔兹曼方法(lattice Boltzmann method,LBM)模型.该模型基于改进的Shan-Chen伪势多相流LBM模型,结合采用不同时间步长的方法,实现密度比达800以上的气液两相流模拟.为了对模型进行验证,模拟了在不同气液相互作用系数和密度比条件下气泡内外压力差与其半径之间的关系,其结果满足Laplace定律.将所建立的大密度比LBM与介观尺度的元胞自动机(cellul arautomaton,CA)和有限差分法(FDM)相耦合,用LBM模拟气液两相流,用CA方法模拟固相生长,用有限差分法模拟温度场,采用LBM-CA-FDM耦合模型对定向凝固过程中凝固前沿的气泡与液-固界面之间的相互作用进行模拟研究.结果表明,绝热气泡的存在影响了温度场分布,使得凝固前沿接近气泡时,液-固界面凸起,在不同的固相生长速度条件下,出现凝固前沿淹没气泡或气泡脱离凝固前沿的不同情况,模拟结果与实验结果符合良好.
10.7498/aps.62.120502

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