2018年春季北京一次沙尘天气边界层特征及来源分析     

桂海林  秦贺  赵培涛  王飞  唐志军  王继康  朱媛媛  褚旸晰 《气象与环境学报》2021,37(4):18-25

2018年3月27—28日,内蒙古中东部、中国东北地区、华北等地出现一次大范围沙尘天气.28日凌晨,沙尘进入北京,受此影响北京出现了严重的污染天气.本文利用中国气象局地面常规观测资料、气溶胶激光雷达、风廓线雷达资料、生态环境部大气成分等资料分析了北京沙尘天气前后边界层特征、沙尘来源以及沙尘天气前后大气污染特征.结果表明...  相似文献   

复杂3D瞬变电磁场FDTD模拟中需要解决的问题     

闫述  傅俏  王刚  曾雪枝 《煤田地质与勘探》2007,35(2):63-66

为了实现缓变瞬态电磁场的时域有限差分(FDTD)模拟,引入了虚拟位移电流,使FDTD随时间步的递推能够进行。在以往较简单模型的计算中,利用时域瞬变场传播需要时间的性质,可将激励源化为初始条件代入,但是对于复杂3D模型,原有的方法不再适用,应当重新考虑源和边界条件的处理方法。由于实际源带有“斜坡”,故可采取将激励源模拟注入的方式;地下边界根据电磁波在导电媒质中快速衰减的特性设定,将改进的完全匹配层用于空中边界。分析表明,对于由空中和地下区域非均匀网格离散引起的时间稳定性问题,交替方向隐式FDTD是可行的解决办法。   相似文献   

利用WRF对兰州冬季大气边界层的数值模拟   总被引：13，自引：5，他引：8  

缪国军  张镭  舒红 《气象科学》2007,27(2):169-175

本文介绍了WRF中尺度模式的有关概况,分析了模式的物理结构,并利用WRF中尺度模式对河谷城市兰州冬季大气边界层的风场和温度场进行了数值模拟研究。模拟结果与观测事实基本一致,表明WRF模式具有良好的稳定性能。  相似文献   

A study on mechanical properties and fracturing behavior of Carrara marble with the flat-jointed model     

Yi Cheng  Louis Ngai Yuen Wong 《国际地质力学数值与分析法杂志》2020,44(6):803-822

Overcoming two inherent limitations presented by the standard bonded-particle model (BPM), the flat-jointed model still lacks extensive application. This study hereby conducts a comprehensive investigation on the application of the flat-jointed model in rock mechanics study. First, after a careful examination on the mechanical behavior of the flat-joint contact, a systematic calibration has been conducted to build numerical models matching the mechanical properties of Carrara marble. Second, the validated model is used to simulate the fracturing behavior of marble specimens containing a single or en-echelon flaws. Finally, the appearance of particle flow code (PFC) models has been compared with the results obtained from optical observation in order to establish a possible correlation between PFC models and real marble regarding microcracking behavior. Discussions suggest that to remove the particle size effect, the model resolution (ratio of sample dimension to the average particle diameter) should be larger than 30 in the flat-jointed model and 150 in the BPM, respectively. Results from the above investigations suggest that the flat-jointed model is capable of matching both the mechanical properties and fracturing behavior of Carrara marble. The numerical model is more reliable to predict the fracturing path at the instant of initiation than at failure. Development of initial fractures is not only controlled by the magnitude of tension force but also influenced by the extent of distribution of tension force. The appearance and components of a fracture in flat-jointed models probably reveal not only its property (tensile or shear) but also the corresponding microcracking behavior of real rocks.  相似文献   

One-dimensional self-weight consolidation with continuous drainage boundary conditions: Solution and application to clay-drain reclamation     

Jianxue Feng  Pengpeng Ni  Guoxiong Mei 《国际地质力学数值与分析法杂志》2019,43(8):1634-1652

Traditional consolidation theories cannot provide good predictions of consolidation settlement in land reclamation because of their assumptions that the influence of soil's self-weight is often neglected, and the drainage boundary is considered as fully pervious/impervious. In view of these limitations, an analytical solution is derived for one-dimensional self-weight consolidation problems with a continuous drainage boundary using the finite Fourier sine transform method. Following the classical Terzaghi's small strain theory, the soil's self-weight is considered to produce consolidation settlement in dredged materials with a constant coefficient of consolidation. The continuous drainage boundary can essentially describe the time-dependent variation of drainage capacity at the interface between two adjacent soil layers. By reducing the interface parameters, the effectiveness of the calculation is demonstrated against the Terzaghi's solution. The influence of interface parameters and soil's self-weight stress coefficient on self-weight consolidation is discussed. As expected, the rate of consolidation considering the self-weight stress is faster, although the dependency of consolidation rate on the material property of void ratio is neglected. Moreover, the plane of maximum excess pore-water pressure is estimated as a function of time factor, based on which a design chart is developed to optimize the layout of horizontal drains in land reclamation.  相似文献   

A coupled 3‐dimensional bonded discrete element and lattice Boltzmann method for fluid‐solid coupling in cohesive geomaterials          下载免费PDF全文

Min Wang  Y.T. Feng  G.N. Pande  T.T. Zhao 《国际地质力学数值与分析法杂志》2018,42(12):1405-1424

This paper presents a 3D bonded discrete element and lattice Boltzmann method for resolving the fluid‐solid interaction involving complicated fluid‐particle coupling in geomaterials. In the coupled technique, the solid material is treated as an assembly of bonded and/or granular particles. A bond model accounting for strain softening in normal contact is incorporated into the discrete element method to simulate the mechanical behaviour of geomaterials, whilst the fluid flow is solved by the lattice Boltzmann method based on kinetic theory and statistical mechanics. To provide a bridge between theory and application, a 3D algorithm of immersed moving boundary scheme was proposed for resolving fluid‐particle interaction. To demonstrate the applicability and accuracy of this coupled method, a benchmark called quicksand, in which particles become fluidised under the driving of upward fluid flow, is first carried out. The critical hydraulic gradient obtained from the numerical results matches the theoretical value. Then, numerical investigation of the performance of granular filters generated according to the well‐acknowledged design criteria is given. It is found that the proposed 3D technique is promising, and the instantaneous migration of the protected soils can be readily observed. Numerical results prove that the filters which comply with the design criteria can effectively alleviate or eliminate the appearance of particle erosion in dams.  相似文献   

A continuum mechanics based framework for optimizing boundary and finite element meshes associated with underground excavations—accuracy,efficiency and applications     

Attila M. Zski  John H. Curran 《国际地质力学数值与分析法杂志》2005,29(13):1299-1315

A framework was developed to address the automatic optimization of the level of geometric detail required for stress analysis of underground excavations in mining, which was presented in the companion paper. The motivation for optimizing the mesh geometry stems from the over‐discretization of computational domain as the digital mine model is built while our knowledge of some of the input parameters is quite limited. Thus, the accuracy of the solution is not expected to be increased with a finely discretized mesh, only the computation time does. Therefore, it is acceptable if the results obtained from an optimized model have accuracy comparable to the uncertainty in input data (e.g. rock mass properties, geology, etc.). Although the mesh optimization framework automates the geometry optimization and reduces computation time, the accuracy of the solution from the resulting geometry must be evaluated to ensure the quality of the solution at the ‘region of interest’. Both a priori (mesh quality) and a posteriori (solution quality) measures are employed along with recording the mesh optimization time. Finally, the applicability of the mesh optimization framework is demonstrated by analysing a number of mining and civil engineering underground models. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   

岫岩金矿控矿断裂生成定位的边界条件和机理     

刘勇胜 《国土资源》1996,(1)

辽宁岫岩金矿是岩浆热液成因的石英脉型金矿床，然而矿区内的一系列石英脉体尽管其空间分布上关系密切，但其矿化程度却有显著差异。本文就这种差异的原因从区域构造应力场－岩体形态－岩石力学性质－控矿（脉）断裂的性质及时、空定位的相关上进行了深入分析探讨，认为岩体形态、岩石物理力学性质是影响断裂时、空定位和性质的主要因素，而且是控制矿化程度差异的根本因素。井由此推断，在１￣＃，２￣＃断裂带南东侧延伸的深部有望找到矿体。  相似文献   

重庆辐射雾的声雷达回波与大气污染特征     

但尚铭  陈国学 《成都信息工程学院学报》1996,(4)

结合气象观测和大气边界层探测资料，分析了１９９０年１月２日重庆雾的声雷达回波特征，并与１９８９年１２月３０日雾的回波作了比较。结果表明，雾顶回波高度与逆温和相对湿度的转折高度一致；雾顶回波在雾的成熟期呈现波动，在消散期有一下降过程。上午大气污染物地面浓度的变化与逆温混合层状况有密切关系，混合层较薄且持续时间较长时，地面浓度较大  相似文献   

基于RFID和自适应卡尔曼滤波的室内移动目标定位方法     

尹姝  陈元橼  仇翔 《南京气象学院学报》2018,10(6):749-753

本文研究了UHF-RFID（超高频-射频识别）环境下的移动目标定位问题,提出了一种结合自适应卡尔曼滤波和BVIRE（边界虚拟参考标签）的移动机器人定位方法,即B-AKF（Boundary-Adaptive Kalman Filter）定位方法.首先,利用UHF-RFID系统对移动机器人进行初始定位,其次,考虑模型和噪声统计特性不确定性,采用自适应卡尔曼滤波方法对机器人的运动状态进行预测和更新,并引入自适应因子补偿噪声方差不确定性问题.最后,搭建了基于UHF-RFID的定位实验平台,并通过实验研究表明,相比于传统的线性BVIRE和线性卡尔曼滤波方法,所提出的自适应卡尔曼滤波方法具有更高的定位精度和更强的鲁棒性能.  相似文献