A Large-Eddy Simulation Study of Turbulent Flow Over Multiscale Topography

Most natural landscapes are characterized by multiscale (often multifractal) topography with well-known scale-invariance properties. For example, the spectral density of landscape elevation fields is often found to have a power-law scaling behaviour (with a −2 slope on a log–log scale) over a wide span of spatial scales, typically ranging from tens of kilometres down to a few metres. Even though the effect of topography on the atmospheric boundary layer (ABL) has been the subject of numerous studies, few have focussed on multiscale topography. In this study, large-eddy simulation (LES) is used to investigate boundary-layer flow over multiscale topography, and guide the development of parametrizations needed to represent the effects of subgrid-scale (SGS) topography in numerical models of ABL flow. Particular emphasis is placed on the formulation of an effective roughness used to account for the increased aerodynamic roughness associated with SGS topography. The LES code uses the scale-dependent Lagrangian dynamic SGS model for the turbulent stresses and a terrain-following coordinate transformation to explicitly resolve the effects of the topography at scales larger than the LES resolution. The terrain used in the simulations is generated using a restricted solid-on-solid landscape evolution model, and it is characterized by a −2 slope of the elevation power spectrum. Results from simulations performed using elevation fields band-pass filtered at different spatial resolutions indicate a clear linear relation between the square of the effective roughness and the variance of elevation.     

阜平岩群下部Sm—Nd同位素年龄及其地质意义

阜平岩群主要分布在太行山北段,是我国太古宙重要的地层单元,并构成阜平深变质绿岩带的岩石组合。前人认为阜平岩群及其区域变质时代主要为新太古代。本次对阜平岩群下部含辉石斜长角闪岩Sm-Nd同位素年代学的详细研究,获得Sm-Nd等时线年龄3352±50Ma和平均模式年龄3374.5Ma,说明阜平岩群底界年龄接近3400Ma,从而也反映阜平深变质绿岩带形成在古—中太古代,是我国目前最老的绿岩带,也是世界上最古老的绿岩带之一。     

Experimental Research on the Erosion Pattern and Protection Using the Extended Modelling Method

-In the paper the extended modelling method with serial sands is used in an experimental re-search on the erosion patterns at the discharge outlet of a beach Hua-Neng power plant.The theoretical ba-sis for the extended modelling method with serial sands is systematically presented in the paper and themethod has been successfully employed in the sediment experiment of coastal works.According to theFroude Law,the model is designed to be a normal one with movable bed,the geometric scaleλ_L=λ_H=15,and three scales of sediment grain size are chosen,i.e.,λ_(d1)=0.207;λ_(d2)=0.393;andλ_(d3)=0.656.The median particle diameter of sea beach prototype sand d_(50p)=0.059mm and the dis-changed water flow of the power plant is 21.7m~3/s.Three types of natural sea sands have been chosen asthe serial modelling sands to extend the simulation of the prototype,thus replacing the conventional test inwhich artificial lightweight sands are used.As a result,this method can not only reduce the costsignificantly,but also it     

天津城市空间资源信息平台建设实践

国土资源管理方式的变革,迫切需要集约化、面向服务的数据支持。本文结合规划和国土资源管理需要,论述天津城市空间资源信息平台的数据整合、数据发布与数据共享。详细介绍了城市空间资源信息平台在规划和国土资源管理、数字城市和城市电子政务中的应用情况,并提出了下一步工作思路。     

基于MO和ArcSDE的城镇地籍建库工具箱开发与应用

城镇地籍数据建库是一项系统性、工程性和技术性相结合的工作。为了高效地、高质 量地、高水平地完成测绘数据的交换处理、权属数据的录入和图属一致控制,开发并 应用一套城镇地籍建库工具集具有极其重要的意义。本文基于MO和ArcSDE设计并 开发了企业级的建库工具箱,集中了各个环节的工具,为北京市城镇地籍建库提供了 有力支持。     

城市高精度实景三维单体模型建设及应用

倾斜摄影测量技术可以实时、综合感知大尺度、高精度的复杂城市场景,在获取正射影像的同时获得真实的立面纹理信息,为城市实景三维模型建设提供保证.本文分析了城市三维单体模型测量基本技术,按照城市要素类型对单体化模型进行分类,研究了二维与三维数据的融合方式,其精细单体化成果在广州市白云区665 km2城市实景三维模型建设中得到...     

千米桥古潜山岩溶地貌演化及古岩溶洞穴发育特征

运用印模法和残厚法以及地震相位追踪对比等古地貌分析法研究揭示,千米桥古潜山岩溶地貌的演化形成先后经历了加里东—海西暴露发育期、印支—燕山暴露改造期、喜马拉雅埋藏定形期等演化阶段。古岩溶洞穴的发育和分布不仅受地貌形态及潜水面的控制,而且与岩性组合、古水文环境及断裂构造密切相关。加里东—海西暴露期地壳的持续抬升和区域潜水面的不断下移,造成古岩溶洞穴的多旋回层状分布,孔洞多被砂泥质充填,有效孔洞保存较少;印支—燕山暴露期发育的古岩溶洞穴受断裂体系影响,分布具有一定随机性,并且多被埋藏期化学半充填,成为目前古潜山油气储层的主要储集空间。利用钻井和测井信息及洞穴充填物,可在生产现场识别古岩溶洞穴的存在及分布,为古潜山油气储层的综合评价提供依据。     

2000年以来贵州省地质矿产勘查开发局科技人员编著出版的地球科学类图书

科技著作是科技人员创造性劳动的结晶。贵州省地矿局加强地质工作,重视科研与生产的紧密结合,在完成生产和科研任务的同时,还撰著、编著、译著了大量科技专著和译著,并公开出版发行。为满足读者了解贵州省地矿局近些年来地质科技的一些进展和图书出版的情况,发挥科技成果的作用