横流条件下垂直动量射流数值模拟

运用标准k-ε紊流模型和易实现k-ε紊流模型对横向流动条件下垂直动量射流的混合特性进行数值模拟.计算结果表明,2个模型均较好地复演了横向流动条件下垂直动量射流的传播和混合过程.在时均特性方面,2个模型的模拟结果相近,计算结果与前人的试验结果吻合较好.在紊动特性方面,计算的紊动强度分布趋势与试验结果吻合较好,且易实现k-ε紊流模型的模拟结果要优于标准k-ε紊流模型,但2个模型都不足以从定量上描述横向射流的紊动特性.     

合成射流流动与传热特征的数值模拟

采用RNGκ-ε模型和PISO算法,通过求解三维N-S方程,对腔体右侧振动膜片运动的二维合成射流流动与传热特征进行了数值模拟.模拟结果显示由于激励器在右侧振动膜片的作用下,合成射流产生的喷射气流在喷口中心右边速度稍大于左边速度,形成不对称射流流场;射流冲击壁面的速度峰值出现在中心区两侧,使得射流冲击换热的Nu数形成相应的峰值;随着合成射流冲击距离Z/do的增大,其对流换热系数出现先增大后减小的变化规律,当冲击距Z/do=20~30 mm时冷却效果较佳.     

用非线性k-ε模型对狭缝冲击射流进行数值计算

采用Ｓｐｅｚｉａｌｅ的非线性ｋ－ε模型和标准的ｋ－ε的模型计算了狭缝冲击射流,给出了径向平均速度和脉动速度沿壁面法向的分布,并同实验结果作了对比．结果表明,当其他条件都相同时,线性和非线性模型在冲击射流的计算中相差不大,今后的改进应当在近壁区或对紊流模型本身进行     

饱和蒸汽在高速过冷水射流外凝结换热的数值模拟

采用数值计算的方法,研究了高速过冷水射流外饱和蒸汽的凝结换热过程,在研究中,采用标准的k-ε紊流计算模型,两相界面上采用了凝结换热边界条件,并考虑了蒸汽凝结造成的相界面处的法向速度,计算表明,凝结换热强度完全由高速过冷水充中的紊流运动决定,其平均对流换热系数可以达到1．0MW／（m2,℃）,与实验结果相符合。     

轴对称紊流射流流场数值模拟

选取标准的Ｋ－ε二方程模型及优选的紊流模型系数，运用有限差分方法对淹没轴对称紊流射流流场进行数值计算．计算结果表明，射流轴心速度是逐渐衰减的，其衰减规律和射流出口雷诺数无关，无因次等速核长度（Ｌ／Ｄ）约为４～５，和实验数据符合较好．对射流径向速度Ｖ沿径向截面的分布及射流基本段内轴向速度分布的相似住进行了预测．     

用非线性κ—ε模型对狭缝冲击射流进行数值计算

采用Ｓｐｅｚｉａｌｅ的非线性κ－ε模型和标准的κ－ε的模型计算了狭缝冲击射流,给出了径向平均速度和脉动速度沿壁面法向的工同实验结果作了对比。结果表明,当其他条件都相同时,线性和非线性模型在冲击射流的计算中相差不大,今后的改进应当在近壁区域对紊流模型本身进行。     

半封闭圆管冲击射流湍流换热数值模拟

采用标准κ-ε模型、RNGκ—ε模型结合壁面函数以及低雷诺数κ—ε模型，对半封闭圆管冲击射流流场的平均速度、湍动能分布和Nu数分布进行了数值计算，并将此3种模型的计算结果与文献中的测量结果进行了比较．结果表明：3种湍流模型都未能完全准确地预测冲击射流场的流动特性与传热特性，其中标准κ—ε模型和低雷诺数κ—ε模型的结果很差，而RNGκ—ε模型的结果与其它两种模型相比更接近实验值。     

用标准k-ε模型求解二维紊动淹没射流

本文认完整的纳维埃—斯托克斯方程出发,分别采用紊动粘性系数为常数的紊流模型相标准k-ε紊流模型,求解船闸中的二维紊动淹没射流。计算结果与实测结果值的比较表明,标准k-ε模型远优于常数模型,它能准确地预测紊动淹没射流涡旋区的非边界层型的复杂流态及紊动动能的分布。     

热辐射对中庭火灾烟流的影响

根据中庭火灾特点，提出了考虑辐射换热损失和壁面传热损失，不考虑燃烧过程视火焰为体积热源，浮升力作用下火灾烟气紊流流动的场模型，引入6通量辐射换热模型，分析热辐射对中庭火灾烟流的影响，并将辐射换热损失计入壁面传热损失，简化辐射换热模型计算，采用PHOENICS通用软件进行数值计算。结果表明，由于中庭温度相对较低，较射换热的影响较小，将壁面传热系数取最大值，从而将辐射换热的影响计入壁面传热损失的计算方法是可行的，应进一步完善数学模型，引入燃烧子模型。     

稳态射流数值模拟中速度参量对传热的影响机制分析

对文献中多个槽缝冲击射流的经典实验结果进行数值模拟,考察RNG k-ε和Transition SST湍流模型的表现,主要分析射流出口中心线和展向、壁面射流区域的雷诺时均速度和湍流度分布,以及靶面换热效果与流场模拟结果之间的关系.模拟结果表明,与Transition SST湍流模型相比,RNG k-ε模型的结果表现出更强的湍流粘性,使得其中心线上速度衰减较快,该效果可能导致低估靶面上的冲击换热效果;而在冲击滞止区域,RNG k-ε湍流模型结果表现出过高的湍动能,该效果可能导致高估靶面上的冲击换热效果.因此,当射流雷诺数较小时,Transition SST模型所得滞止区换热系数要高于RNG k-ε模型的结果,反之亦然;而在壁面射流区域,RNG k-ε模型对于流场速度的模拟较好,但相应区域的传热模拟并没有表现出明显的优越性.     

An Index mechanism for multi-scale view in spatial databases

There are numerous geometric objects stored in the spatial databases. An importance function in a spatial database is that users can browse the geometric objects as a map efficiently. Thus the spatial database should display the geometric objects users concern about swiftly onto the display window. This process includes two operations:retrieve data from database and then draw them onto screen. Accordingly, to improve the efficiency, we should try to reduce time of both retrieving object and displaying them. The former can be achieved with the aid of spatial index such as R-tree, the latter require to simplify the objects. Simplification means that objects are shown with sufficient but not with unnecessary detail which depend on the scale of browse. So the major problem is how to retrieve data at different detail level efficiently. This paper introduces the implementation of a multi-scale index in the spatial database SISP (Spatial Information Shared Platform) which is generalized from R-tree. The difference between the generalization and the R-tree lies on two facets: One is that every node and geometric object in the generalization is assigned with a importance value which denote the importance of them, and every vertex in the objects are assigned with a importance value,too. The importance value can be use to decide which data should be retrieve from disk in a query. The other difference is that geometric objects in the generalization are divided into one or more sub-blocks, and vertexes are total ordered by their importance value. With the help of the generalized R-tree, one can easily retrieve data at different detail levels.Some experiments are performed on real-life data to evaluate the performance of solutions that separately use normal spatial index and multi-scale spatial index. The results show that the solution using multi-scale index in SISP is satisfying.     

Characterization of Ordovician carbonate reservoirs, southeastern Saskatchewan, Canada

The discovery of the prolific Ordovician Red River reservoirs in 1995 in southeastern Saskatchewan was the catalyst for extensive exploration activity which resulted in the discovery of more than 15 new Red River pools. The best yields of Red River production to date have been from dolomite reservoirs. Understanding the processes of dolomitization is, therefore, crucial for the prediction of the connectivity, spatial distribution and heterogeneity of dolomite reservoirs.The Red River reservoirs in the Midale area consist of 3～4 thin dolomitized zones, with a total thickness of about 20 m, which occur at the top of the Yeoman Formation. Two types of replacement dolomite were recognized in the Red River reservoir: dolomitized burrow infills and dolomitized host matrix. The spatial distribution of dolomite suggests that burrowing organisms played an important role in facilitating the fluid flow in the backfilled sediments. This resulted in penecontemporaneous dolomitization of burrow infills by normal seawater. The dolomite in the host matrix is interpreted as having occurred at shallow burial by evaporitic seawater during precipitation of Lake Almar anhydrite that immediately overlies the Yeoman Formation. However, the low δ18O values of dolomited burrow infills (-5.9‰～ -7.8‰, PDB) and matrix dolomites (-6.6‰～ -8.1‰, avg. -7.4‰ PDB) compared to the estimated values for the late Ordovician marine dolomite could be attributed to modification and alteration of dolomite at higher temperatures during deeper burial, which could also be responsible for its 87Sr/86Sr ratios (0.7084～0.7088) that are higher than suggested for the late Ordovician seawaters (0.7078～0.7080). The trace amounts of saddle dolomite cement in the Red River carbonates are probably related to "cannibalization" of earlier replacement dolomite during the chemical compaction.     

A computer generator for randomly layered structures

AcomputergeneratorforrandomlylayeredstructuresYUJia shun1,2,HEZhen hua2(1.TheInstituteofGeologicalandNuclearSciences,NewZealand;2.StateKeyLaboratoryofOilandGasReservoirGeologyandExploitation,ChengduUniversityofTechnology,China)Abstract:Analgorithmisintrod…     

Perspherical Approaches for Electrons in Atoms and Charged Excitons in Quantum Wells

Instead of following Fock’s expansion,we solve the Schrodinger equation for some quantum mechanical manybody systems such as electrons in atoms and charged excitons in quantum wells in a similar way in hyperspherical coordinates by expanding the wave functions into orthonormal complete basis sets of the hyperspherical hannonics(HHs)of hyperangles and generalized Laguerre polynomials(GLPs)of the hyperradius.This leads the equation to     

Advances in broadband wireless communications under high-mobility scenarios

Future mobile communication systems aim at providing very high data transmission rates, even in high-mobility scenarios such as high-speed wheel-track trains, maglev trains, highway vehicles, airplanes, guided missiles or spacecraft. A particularly important commercial application is the strong and increasing worldwide demand for high- speed broadband wireless communications （up to 574.8 km/ h test speeds or 380 km/h commercial speeds） in railways, providing data, voice and video services for applications such as onboard entertainment services to passengers, train control, train dispatch, train sensor status handling and sur- veillance. In such high-mobility scenarios, there are a number of communication challenges, including fast hand- over, location updating, high-speed channel modeling, estimation and equalization, anti-Doppler spreading tech- niques, fast power control, and dedicated network architec- ture. Because signal transmission in very high-speed scenarios will inevitably experience serious deterioration, it is imperative to develop key broadband mobile communi- cation techniques for such high-speed vehicles.     

Wuhan University Journal of Natural Sciences TOTAL CONTENTS

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海南岛地体及其毗邻陆缘晚中生代—新生代古地磁研究和构造演化

本文叙述了对海南岛及其毗邻大陆边缘白垩纪到第四纪地层岩石进行古地磁研究的全部工作过程。通过分析岩石中剩余磁矢量的磁偏角及磁倾角的变化,提出海南岛白垩纪以来经历的构造演化模式如下:早期伴随顺时针旋转而向南迁移,后期伴随逆时针转动并向北运移。联系该地区及邻区的地质、地球物理资料,对海南岛上述的构造地体运动提出以下认识:北部湾内早期有一拉张作用,主要是该作用使湾内地壳显著伸长减薄,形成北部湾盆地。从而导致了海南岛的早期构造运动,而海南岛后期的构造运动则主要是受南海海底扩张的影响。海南地体运动规律的阐明对于了解北部湾油气盆地的形成演化有重要的理论和实际意义。     

Scale-based spatial data model for GIS

Being the primary media of geographical information and the elementary objects manipulated, almost all of maps adopt the layer-based model to represent geographic information in the existent GIS. However, it is difficult to extend the map represented in layer-based model. Furthermore, in Web-Based GIS, It is slow to transmit the spatial data for map viewing. In this paper, for solving the questions above, we have proposed a new method for representing the spatial data. That is scale-based model. In this model we represent maps in three levels: scale-view, block, and spatial object, and organize the maps in a set of map layers, named Scale-View, which associates some given scales.Lastly, a prototype Web-Based GIS using the proposed spatial data representation is described briefly.     

Exciton Seebeck in Molecular Systems

Various applications relevant to the exciton dynamics,such as the organic solar cell,the large-area organic light-emitting diodes and the thermoelectricity,are operating under temperature gradient.The potential abnormal behavior of the exicton dynamics driven by the temperature difference may affect the efficiency and performance of the corresponding devices.In the above situations,the exciton dynamics under temperature difference is mixed with     

Achieving Unusual States of Matter Under High Pressure

The elongation method,originally proposed by Imamura was further developed for many years in our group.As a method towards O(N)with high efficiency and high accuracy for any dimensional systems.This treatment designed for one-dimensional(ID)polymers is now available for three-dimensional(3D)systems,but geometry optimization is now possible only for 1D-systems.As an approach toward post-Hartree-Fock,it was also extended to