直接控制网格节点分布的网格生成生方法

本文采用了一种利用边界网格节点分布信息来控制区域内部网格节点分布的网络生成技术。使用该方法可以在给定边界网格节点坐标值后，不采用任何技巧便可生成按要求加密的网格。为使生成的网格满足边界正交性，本文对上述方法作了改进，取得了良好的效果。     

二维粘性流动的边界元方法

本文叙述了粘性流动边界元方法，并研究了动力润滑，涡旋发生以及生物力学等问题。该方法基于用Ｓｔｏｌｅｓ方程的基本解作为格林函数，将Ｎ－Ｓ方程归结为求解区域边界上的积分方程，使用边界单元，数值求解积分方程，给出了应力分布、压力分布及速度场。数值结果与理论结果和实验结果十分符合，方法具有很高的精度，比起目前的差分法和有限元法，在某些问题上更有效，也更灵活。     

基于非结构网格的长江口二维三维嵌套潮流数值模拟

三维数学模型多应用于局部水域,无法模拟模型周边的大范围流场.为解决此问题,基于非结构网格有限体积法,建立了长江口二维三维潮流嵌套数学模型.模型嵌套边界采用近似处理方法,假设嵌套边界处网格单元分层水平流速服从多项式分布,该处理方法嵌套边界处的三维计算存在一定误差.将模型应用于长江口大范围水域潮流模拟计算.结果表明,潮位及二维三维潮流验证良好,计算精度满足规范要求,这说明该方法能够模拟大范围水域的二维及三维潮流运动.     

直接控制网格节点分布的网格生成方法

本文采用了一种利用边界网格节点分布信息来控制区域内部网格节点分布的网格生成技术.使用该方法可以在给定边界网格节点坐标值后,不采用任何技巧便可生成按要求加密的网格.为使生成的网格满足边界正交性,本文对上述方法作了改进,取得了良好的效果.     

一种改进的多传感器系统网格状分簇路由协议算法(英文)

针对现有的多传感器网络系统分簇路由协议负载能量不均衡、簇头节点分布不均、网络生命期较短等问题,设计了一种新的网格状分簇路由协议算法(New Grid Clustering Hierarchy,NEWGRID).该算法利用网格分割技术将区域分割为等大的均匀区域,在以网格交叉节点为圆心的某个圆范围内进行簇头选举.该路由协议引入阈值函数选择簇头.当节点剩余能量高于阈值函数时,节点竞争为候选簇头,同时区域簇首与基站之间的通信由传统的单跳切换为多跳.仿真实验结果表明,该算法比现有的算法在多传感器网络系统能量消耗、数据吞吐量、簇头节点分布方面具有明显优势.     

曲线拟合坐标变换技术在三角形网格生成中的应用

将拟事坐标变换技术应用于三角形网格生成中，形成一种方便、有效的三角形网格生成方法。该方法直接利用边界网格节点的分布信息来控制区域内部网格节点的分布，在数值模拟河道、湖泊等复杂边界的地流速场时，可快速获得一种适应物理量场变化情形的三角形网格系统，使基差该网格系统的流场计算精度明显提高。     

河道油藏的自适应网格积分方程粗化算法

本文以河道的观测深度为确定性数据由贝叶斯理论通过随机建模的方法生成横截面为抛物线形状的河道油藏边界面。在粗网格内先统计渗透率在粗化网格的概率分布,然后由渗透率积分方程利用渗透率在粗化网格中的概率分布计算粗化网格的等率渗透率,再利用等效渗透率计算粗化网格的压强分布。计算压强时并将渗透率自适应网格技术应用于河道油藏的粗化算法中。在渗透率或孔隙度变化异常区域自动采用精细网格,用直接解法求解渗透率或孔隙度变化异常区域的压强分布,整个区域还采用了不均匀网格。利用本文方法计算了河道油藏的压强分布,结果表明河道油藏的不均匀自适应网格积分方程粗化算法的解在渗透率或孔隙度异常区的压强分布规律更逼近采用精细网格的解,在其他区域压强分布规律非常逼近粗化算法的解,但计算的速度比采用精细网格提高了100多倍。     

一种适于复杂形状物体绕流计算的网格生成方法

本文给出了一种适用于复杂形状边界下进行复杂流动数值模拟的有效的网格生成方法，该方法将求解域分成若干个子域，由子域边界点分布来确定Ｐｏｉｓｓｏｎ方程源项，从而控制求解域内点分布，在全场求解Ｐｏｉｓｓｏｎ方程。所生成的网格质量高，且避免了用普通ＴＴＭ法生成网格时，网格疏密分布的控制过于依赖于经验参数的选择的缺点，作为例证，给出了环量控制翼型绕流的数值模拟结果。     

LBM的一种新的边界处理方法

近年来,LBM取得了长足的进展,理论和应用方面都有了新的突破,各种新的模型和边界处理方法不断被提出.在这些边界处理方法基础上,本文提出了一种新的边界处理方法,该方法是用邻点和次邻点的宏观值二阶插值得到边界上的宏观值,再用邻点的分布函数的非平衡部分来外推得到边界处的分布函数.此方法可用于压力边界或速度边界,具有二阶精度,采用该处理方法对Poiseuille流、Couette流和Cavity流进行了数值模拟,并与其他几种边界处理作了比较,其结果要好于其他几种边界处理.     

近似正交的曲线网格生成技术研究

基于Thompson曲线网格生成方法,导出一组新的调节函数P、Q的表达式,并给出了曲线网格生成实例。实例检验表明,该调节函数能够对复杂边界的单连通域或多连通域生成理想的曲线网格,即网格近似正交,网格分布能够适应物理量场变化的情形。在实际水利工程流场数值模拟中,该方法能够准确地使用边界条件,提高求解精确度。     

液滴冲击液面的格子Boltzmann仿真研究

应用格子Boltzmann两相流方程，结合水平集界面重构技术，提出两相流的数值模型。采用五阶WENO格式和三阶TVD Runge-Kutta格式来求解Level Set 函数的输运方程。在不计重力的条件下，对液滴平动进行了数值模拟，在计算了800个时间步后，平动的液滴仍然保持原来的形状。在考虑重力的条件下，对液滴在空气中自由下落、液滴冲击液面的全过程进行了数值模拟，计算结果精细地刻画了液滴和液面界面的变化过程。数值模拟结果与物理规律一致。     

SOLUTE TRANSPORT IN NATURAL FRACTURES BASED ON DIGITAL IMAGE TECHNOLOGY

A method of fracture boundary extraction was developed using the Gaussian template and Canny boundary detection on the basis of the collected digital images of natural fractures. The roughness and apertures of the fractures were briefly discussed from the point of view of digital image analysis. The extracted fractured image was translated into a lattice image which can be directly used in numerical simulation. The lattice Boltzmann and modified moment propagation mixed method was then applied to the simulation of solute transport in a natural single fracture, and this mixed method could take the advantages of the lattice Boltzmann method in dealing with complex physical boundaries. The obtained concentrations was fitted with the CXTFIT2.1 code and compared with the results obtained with the commercial software Feflow. The comparison indicates that the simulation using the mixed method is sound.     

基于改进FV-LBM的多孔介质渗流模拟

提出了一种新的基于Brimman -Forchheimer方程的多孔介质流动格子Boltzmann法的有限体积形式（FV-LBM）。在该方法中,多孔介质效应通过将外力引入格子Boltzmann方程中,并通过以单元为中心的有限体积法求解,同时将权重的校正因子引入进来以提高数值计算的稳定性。用该方法验证了完全多孔Poiseuille流和Couette流,数值计算结果与理论解吻合较好。而且还用该方法模拟了具有均匀和非均匀孔隙度的裂隙-孔隙模型,结果表明：当达西数增加时,多孔层中的速度增加;而当裂隙区域的速度峰值减小时,速度轮廓接近抛物线。研究成果为多孔介质渗流模拟提供了有效途径。     

Lattice Boltzmann simulations of oscillating-grid turbulence

The lattice Boltzmann method is used to simulate the oscillating-grid turbulence directly with the aim to reproduce the experimental results obtained in laboratory. The numerical results compare relatively well with the experimental data through determining the spatial variation of the turbulence characteristics at a distance from the grid. It is shown that the turbulence produced is homogenous quasi-isotropic in case of the negligible mean flow and the absence of secondary circulations near the grid. The direct numerical simulation of the oscillating-grid turbulence based on the lattice Boltzmann method is validated and serves as the foundation for the direct simulation of particle-turbulence interactions.     

Lattice Boltzmann simulation of the open channel flow connecting two cascaded hydropower stations

This paper examines the feasibility and the efficiency of a multiple-relaxation-time lattice Boltzmann model(MRT-LBM) for simulating open channel flows in engineering practice. A MRT-LBM scheme for 2-D shallow water flows taking into account of the bed slope and the friction is proposed. The scheme's reliability is verified by benchmark problems and the simulation capability is improved by implementing the scheme on a graphic processing unit(GPU). We use the method to analyze the flow characteristics in the connecting open channel of two cascaded hydropower stations. The flow fields and parameters such as the water depth, the flow rate, and the side-weir discharge, under different operating conditions, are analyzed. The factors affecting the accuracy and the efficiency are discussed. The results are found to be reasonable and may be used as a guidance in the project design. It is shown that the GPU-implemented MRT-LBM on a fine mesh can efficiently simulate two-dimensional shallow water flows in engineering practice.     

RESEARCH ON THE MIXING LAYER OF FIBER SUSPENSIONS AND DIRECT SIMULATION ON THE MOTION OF CYLINDRICAL PARTICLES

The mixing layer of fiber suspensions was simulated numerically with the spectral method and the fibers in the flow were traced individually with calculation. The corresponding experiments were made. The results show that the Stokes number of particles is the key parameter to determine the spatial distribution of fibers and the coherent structures control the orientation of fibers. Direct simulations of the motion of cylindrical particles were carried out via lattice Boltzmann method. It is found that the aspect ratio of particles has significant effects on the translation and rotation of the cylindrical particles. A new lattice Boltzmann method which is convenient to deal with the curved boundary is proposed.     

LATTICE BOLTZMANN SCHEME TO SIMULATE TWO-DIMENSIONAL FLUID TRANSIENTS

ＮＯＭＥＮＣＬＡＴＵＲＥｐα ———ｐｒｅｓｓｕｒｅｄｉｓｔｒｉｂｕｔｉｏｎｆｕｎｃｔｉｏｎｐ(0 )α ———ｅｑｕｉｌｉｂｒｉｕｍｄｉｓｔｒｉｂｕｔｉｏｎｆｕｎｃｔｉｏｎｅα———ｌｏｃａｌｐａｒｔｉｃｌｅｓｔｒｅａｍｖｅｌｏｃｉｔｙｒ———ｌｏｃａｔｉｏｎｏｆｃｏｍｐｕｔａｔｉｏｎａｌｇｒｉｄｎｏｄｅδｔ ———ｔｉｍｅｉｎｃｒｅｍｅｎｔτ———ｔｈｅＢＧＫｒｅｌａｘａｔｉｏｎｐａｒａｍｅｔｅｒα———ｉｎｄｅｘｏｆｐａｒｔｉｃｌｅｓｔｒｅａｍｄｉｒｅｃｔｉｏｎｂ———ｔｈｅｎｕｍｂｅｒｏｆｐａ…     

用格子Boltzmann方法模拟平板层流边界层流动

本文应用格子Boltzmann方法模拟了平板层流边界层流动。考虑到平板边界的影响，我们对模型进行了修正，在标准格子Boltzmann方程中引入压力修正项。该项满足一定的假定条件，从而消除了压缩性引起的偏差。作为算例，我们用修正的模型计算了平板层流边界层流动，并与经典的Blasius解及Lavallee的格子气自动机结果进行了比较，结果是可以接受的。     

APPLICATION OF LBM-SGS MODEL TO FLOWS IN A PUMPING-STATION FOREBAY

A 2-D Lattice Boltzmann Method (LBM) coupled with a Sub-Grid Stress (SGS) model is proposed and validated by flows around a non-submerged spur dike in a channel. And then the LBM-SGS model is further applied to flows in a pumping-station forebay. Shallow water equations are numerically solved by the LBM and the turbulence can be taken into account and modeled efficiently by the Large Eddy Simulation (LES) model. The bounce-back scheme of the non-equilibrium part of the distribution function is used at the inlet boundary, the normal gradient of the distribution function is set as zero at the outlet boundary and the bounce-back scheme is applied to the solid wall to ensure non-slip boundary conditions. Firstly, the model successfully predicts the flow characteristics around a spur dike, such as circulating flow, velocity and water depth distributions. The results are verified by the experimental data and compared to the results obtained by conventional Smagoringsky Model (SM) of LES. Finally, the LBM-SGS model is used to further predict the flow characteristics in a forebay, such as secondary flow and water level. The comparisons show that the model scheme has the capacity to simulate complex flows in shallow water with reasonable accuracy and reliability.     

Numerical simulation of hemodynamic interactions of red blood cells in micro-capillary flow

The hemodynamic interactions of red blood cells （RBCs） in a microcapillary flow are investigated in this paper. This kind of interaction is considered as the non-contact mutual interaction of cells, which is important in the suspension flow of blood, but not sufficiently understood. The distributed Lagrange multiplier/fictitious domain method in the lattice Boltzmann framework is used to solve the suspension of the RBCs. The modification of the flow due to the cells, the dependence of the cell deformation on the flow and the cell-cell interaction via the fluid are discussed. It is revealed that the long-range hydrodynamic interaction with a long interacting distance, more than about 5 times of the RBC equivalent radius, mainly has effect on the rheology properties of the suspension, such as the mean velocity, and the short-range interaction is sensitive to the shape of the cell in the microcapillary flow. The flow velocity around the cell plays a key role in the cell deformation. In the current configuration of the flow and cells, the cells repel each other along the capillary.