脉动流条件下圆柱绕流特性研究

该文数值研究了脉动流条件下圆柱绕流场特性,对涡量分布、升阻力系数、升力系数频谱特性等进行了分析。结果表明,脉动流作用会使圆柱尾涡剪切层变薄,提高脉动频率使尾涡长度变短、脱离加快,提高无量纲脉动振幅使主导涡的脱落速度降低,使旋涡生成区域更靠近圆柱表面;脉动频率与无量纲脉动振幅的增大使升、阻力系数的振幅均增大,而且与升力系数相比,阻力系数的振幅更大,变化更快;升力系数频谱图存在多个主频,包括旋涡脱落频率和相位叠加频率,其中旋涡脱落频率的振幅随着脉动频率的增加而减小,随着无量纲脉动振幅的增加而增加。     

脉动流条件下的圆柱绕流特性研究

为探究脉动流对流体绕流结构物产生的影响,采用数值方法研究了脉动流条件下圆柱绕流场特性,对涡量分布、升阻力系数、升力系数频谱特性等进行分析。结果表明:脉动流作用会使圆柱尾涡剪切层变薄,提高脉动频率使尾涡长度变短、脱离加快,提高无量纲脉动振幅使主导涡的脱落速度降低,使旋涡生成区域更靠近圆柱表面;脉动频率与无量纲脉动振幅的增大使升力系数、阻力系数的振幅均增大,而且与升力系数相比,阻力系数的振幅更大,变化更快;升力系数频谱图存在多个主频,包括旋涡脱落频率和相位叠加频率,其中旋涡脱落频率的振幅随着脉动频率的增加而减小,随着无量纲脉动振幅的增加而增加。在流场中加入脉动流,可以增强流体振动促进流动混合。     

高负荷扩压叶栅二维非定常数值模拟

为探究高负荷扩压叶栅在大正冲角下的非定常流动机理,应用数值方法与拓扑分析理论考察了大正冲角下叶栅内分离旋涡的发展过程,并分析了旋涡运动对流场参数的影响.结果表明,+15°冲角下叶栅内主要存在吸力面分离涡和尾缘涡,吸力面分离涡的脱落频率为104.7 Hz,尾缘涡和吸力面分离涡交替脱落形成两倍频211.5 Hz;分离涡在发展过程中会抑制和归并弱小旋涡,同时还会使叶片的局部气动负荷明显上升.     

半潜式风电机组平台水动力模型试验及数值模拟研究

针对某深远海漂浮式风电机组运动响应受风载荷影响的问题,进行了缩尺模型的水池试验以及实尺模型的数值模拟计算：根据水池自由衰减试验得到的自由衰减曲线及衰减消灭曲线,对基于势流边界元建立的数值模型进行了必要的阻尼修正;用数值方法计算得到的平台运动RAO结果与水池试验生成白噪声非规则波时测量得到的平台运动响应结果进行了对比分析,确保了所建立数值模型的准确性,同时验证了白噪声非规则波试验的可行性;通过时域及频域数值计算方法与试验方法相结合,对比研究了恒风条件下和无风条件下白噪声非规则波作用时平台的运动响应,以及相关的波浪载荷与风载荷的幅值与相位频谱．根据上述计算及研究结果,最终初步总结出了风载荷对风电平台半潜式浮式基础的运动响应的主要影响形式及原因．研究结果表明：风载荷对平台运动的影响与风、浪载荷主要频率成分处频率、幅值以及相位有关．在风载荷与波浪载荷的能量集中频率基本一致,且与平台运动固有频率相重叠时,风载荷的影响会得以显著体现(本文中差异约22%),而影响的形式(增强或削弱运动幅值)则取决于此时风载荷与波浪载荷的相位差：当风、浪载荷同相位时,联合载荷作用下相关自由度的运动幅值将显著增大,反之...     

数值分析串列双圆柱绕流

为研究不可压缩流动中二维的串列双圆柱中不同间距对圆柱间相互作用和尾流特征的影响,选取间距比L/D(L为两圆柱中心间的距离,D为圆柱直径)为2、3、4共3个间距进行了数值分析.计算均在Re=200的非定常条件下进行.计算了圆柱的升阻力系数、尾涡脱落频率等描述绕流问题的主要参量.并与参考文献的数值结果比较,验证了用FLUENT分析的有效性.     

串列双桥墩紊流特性研究

采用概化水槽试验和数值模拟相结合的方法,建立了水流与桥墩的二维概化水槽模型。通过对迹线、尾涡强度及脱落频率的研究,分析了桥墩间距对桥墩周围紊流特性的影响。研究结果表明,串列双桥墩间距较小(L/D≤2.0)时,上游桥墩没有形成涡的脱落,上游桥墩的剪切层交替的附着在下游桥墩上,导致剪切层在运动之前变厚,尾涡脱落频率减小,紊动强度增大;当3.0≤L/D5.0时,上、下游桥墩均有涡的脱落,且桥墩间距越大涡脱落现象越明显,尾涡的紊动强度随间距的增大而减小;当桥墩间距增大到5.0后,上、下游尾涡的紊动及尾涡脱落类似单个桥墩。     

圆盘近尾迹中低频不稳定特性研究

利用大涡模拟(LES)和热线实验测量手段,采用小波分析及FFT方法对Re=104的圆盘近尾迹中的特征频率进行了捕捉,着重对低频不稳定性进行了研究.LES和热线实验结果表明,圆盘近尾迹中除对应于剪切层Kelvin-Helmholtz不稳定的高频率StKH≈1.6和大尺度涡旋脱落频率StV≈0.14外,还存在两个低频率:StL1≈0.02和StL2≈0.03.进一步对导致低频不稳定性的物理机制进行了分析,发现低频率StL1≈0.02与涡旋脱落周向旋转有关,而低频率StL2≈0.03与回流区的伸缩运动有关.本研究合理解释了目前钝体绕流低频数值分散的原因.     

三边形桅杆杆身风荷载特性风洞试验研究

应用高频测力天平技术,分别对有附属结构和无附属结构的三边形桅杆杆身进行了均匀流和两种紊流下的风洞试验,得到了桅杆的平均风力系数、均方根力系数和顺风向、横风向及扭转向风荷载谱.分析了雷诺数、紊流度、风向角、附属结构等对风荷载系数的影响,对比了试验体型系数和不同国家规范关于桅杆及其附属结构体型系数的规定.谱分析结果表明,顺风向风荷载谱和脉动风速谱的基本特征相同,横风向、扭转向风荷载谱主要由低频部分的紊流激励谱和高频部分的旋涡脱落激励谱组成,无附属结构模型旋涡脱落谱有一个峰,峰值折减频率在1.8左右,带附属结构模型在90°风向角下出现两个明显的旋涡脱落谱峰,峰值折减频率分别在0.9和2.2左右,探讨了格构式塔架旋涡脱落谱的特性以及附属结构对其的影响机理.     

既有拱桥光彩亮化改造后吊索的涡振性能

为确定既有拱桥亮化改造后柔性吊索的涡激共振性能，结合数值模拟和风洞试验 开展了研究 . 针对既有吊索和新增吊索的亮化方案，对典型断面在不同来流风向下的绕流特 性进行了模拟，并讨论了气动力系数和旋涡脱落行为随风向角的演变规律. 然后，通过节段模 型风洞试验测试了吊索在不同风向角来流作用下的涡振响应，并结合数值模拟的结果对试验 现象进行了分析. 结果表明：在既有吊索上安装亮化灯具显著改变了其涡振性能. 当来流风垂 直于桥轴线时，沿索轴方向两种典型截面的旋涡脱落频率、强度有较大差异，减小了吊索整体 发生涡激共振的可能；当来流风向角在 30°附近时，两种典型截面的旋涡脱落特性趋于一致， 增大了吊索整体发生涡激共振的可能 . 新增吊索更为轻柔，外包矩形灯罩后发生涡激共振的 可能性很大，需要考虑必要的抑振措施.     

串列双圆柱绕流问题数值模拟的多尺度分析

运用有限体积法,对串列放置的双圆柱二维不可压缩流动进行了直接数值计算.在分析Strouhal数及升阻力系数等积分量的基础上,本文从流动多尺度层面研究了流场分布及涡结构.通过对速度场的流动显示和频谱分析,确定了涡脱落的多个频率,以及分别受上游圆柱和下游圆柱边界层扰动形成的多尺度涡的相互作用,并且发现由于多尺度涡的相互作用形成了更小尺度涡的过程及机理.最后,进一步将这些涡结构与流场模态对应起来,使得流场结构更加清晰地展现出来.     

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…     

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。     

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     

《Chinese Science Bulletin》SUBJECT INDEX TO VOLUME 59(2014)

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An on-line scaling method for improving scalability of a database cluster

The explosive growth of the Internet and database applications has driven database to be more scalable and available, and able to support on-line scaling without interrupting service. To support more client's queries without downtime and degrading the response time, more nodes have to be scaled up while the database is running. This paper presents the overview of scalable and available database that satisfies the above characteristics. And we propose a novel on-line scaling method. Our method improves the existing on-line scaling method for fast response time and higher throughputs. Our proposed method reduces unnecessary network use, i.e. , we decrease the number of data copy by reusing the backup data. Also, our on-line scaling operation can be processed parallel by selecting adequate nodes as new node. Our performance study shows that our method results in significant reduction in data copy time.     

An improved R-tree based on childnode''s probability

R-Tree is a good structure for spatial searching. But in this indexing structure,either the sequence of nodes in the same level or sequence of traveling these nodes when queries are made is random. Since the possibility that the object appears in different MBR which have the same parents node is different, if we make the subnode who has the most possibility be traveled first, the time cost will be decreased in most of the cases. In some case, the possibility of a point belong to a rectangle will shows direct proportion with the size of the rectangle. But this conclusion is based on an assumption that the objects are symmetrically distributing in the area and this assumption is not always coming into existence. Now we found a more direct parameter to scale the possibility and made a little change on the structure of R-tree, to increase the possibility of founding the satisfying answer in the front sub trees. We names this structure probability based arranged R-tree (PBAR-tree).     

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.     

Integrating GIS Web services based on mediating architecture

The geographic information service is enabled by the advancements in general Web service technology and the focused efforts of the OGC in defining XML-based Web GIS service. Based on these models, this paper addresses the issue of services chaining,the process of combining or pipelining results from several interoperable GIS Web Services to create a customized solution. This paper presents a mediated chaining architecture in which a specific service takes responsibility for performing the process that describes a service chain. We designed the Spatial Information Process Language (SIPL) for dynamic modeling and describing the service chain, also a prototype of the Spatial Information Process Execution Engine (SIPEE) is implemented for executing processes written in SIPL. Discussion of measures to improve the functionality and performance of such system will be included.