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221.
The influence of swirl on the shape of the Burke-Schumann reaction sheet in a straight cylindrical pipe is investigated by asymptotic and numerical means. Attention is confined to swirl levels that are near the critical value at which vortex breakdown occurs. A high-Reynolds-number, laminar, isothermal, low-Mach-number reacting flow is considered. An asymptotic analysis is developed to study the nonlinear interaction between near-critical swirl and mixture fraction distribution within the flow. It is first shown that leading-order perturbation of the velocity field from the columnar state, generated by the interaction of near-critical swirl and low viscosity, can be described by a nonlinear reduced-order model. This flow perturbation is computed, and then employed to determine the correction to the classical Burke-Schumann solution. Under lean conditions of reaction the reaction sheet becomes shorter and more compact as swirl is increased. For rich conditions of reaction, increasing swirl first causes the reaction-sheet length to decrease, and then increase after vortex breakdown has appeared. Numerical simulations of the flow and reaction-zone shape are substantiated by, and supplement, the asymptotic results. 相似文献
222.
Forecasting subtle traps by sequence stratigraphy and 3D seismic data is a sensitive topic in hydrocarbon exploration. Research
on subtle traps by geophysical data is the most popular and difficult. Based on the sufficiently drilling data, log data,
core data and 3D seismic data, sediment sequence of Qikou depression, Huanghua basin was partitioned by using sequence stratigraphy
theory. Each sediment sequence system mode was built. Sediment faces of subtle traps were pointed out. Dominating factors
forming subtle traps were analyzed. Sandstone seismic rock physics and its response were studied in Tertiary System. Sandstone
geophysical response and elastic modulus vary laws with pressure, temperature, porosity, depth were built. Experimental result
and practice shows that it is possible using seismic information forecasting subtle traps. Integrated using geology, log,
drilling data, special seismic processing technique, interpretation technique, high precision horizon calibration technique,
3D seismic visualizing interpretation, seismic coherence analysis, attribute analysis, logging-constrained inversion, time
frequency analysis, subtle traps object is identified and interpreted. Finally, advantage object of subtle trap in this area
was determined. Bottomland sand stratigraphic and lithologic reservoirs in Qinan slope zone have been founded by means of
high resolution 3D seismic data field technique, high resolution 3D seismic data processing technique and seismic wave impedence
inversion technique.
Foundation item: Project(2003034470) supported by the Postdoctoral Science Foundation of China; project supported by the Postdoctoral Science
Foundation of Central South University 相似文献
223.
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225.
通过构造格局研究、沉积相及储集特征研究、储集层预测评价、储集层分布发育特点、油气水分布聚集规律及影响因素分析,认为吉格森构造带面向生油洼槽,良好的沉积砂体、发育的构造图闭与之相匹配,使之成为额仁淖尔凹陷的主要油气聚集带。据此指导油田滚动勘探开发,寻找出数百万吨地质储量,使构造带成为千万吨级大油田。 相似文献
226.
苏北盆地白驹凹陷深层油气成藏研究 总被引:8,自引:0,他引:8
通过有机相分析、二次生烃机理研究、油气成藏静态要素和动态要素分析,对苏北盆地白驹凹陷深层油气成藏进行研究。认为:白驹凹陷深层烃源岩有机相包括B、B1和D亚相,下寒武统幕府山组(∈1mu)、下志留统高家边组(S1g)烃源岩为B亚相,生油气潜力大;无论一次生烃还是二次生烃,烃源岩总的产烃能力是一定的,二次生烃与一次生烃有一定连续性;白驹凹陷深层烃源岩二次生烃史极为复杂,大致经历了加里东期、海西-印支期、燕山期、燕山晚期-喜山期;根据成藏基本要素的不同,白驹凹陷深层油气成藏模式可分为下部油气成藏模式(下古生界)和上部油气成藏模式(上古生界)。 相似文献
227.
In the southeast in Norrköping, Sweden, is a small fjord-like bay called Slätbaken. The water quality in Slätbaken—with its narrow outlet to the Baltic Sea—depends highly on the water quality of the streams that flow in it. While point pollution sources can be identified easily in general, the non-point sources are harder to find. The most important sources for non-point pollution are agricultural areas, and the pollutants are mostly nutrients like phosphorus, which come from the fertilisation of the fields. One important catchment area for Slätbaken is the 57.7 km2 Gisselö river basin (part of the topographic map 8GNO), which contains large agricultural areas.The transport of water pollutants is based on the same hydrological processes as erosion and sediment transport. The implementation of such a model in a GIS allows the analysis of a large area with a high resolution. When choosing the model, special attention was paid to the possibility of using a verified model that is easy to implement in a commercial GIS without the need of too much expert knowledge. This may allow its widespread use in many administrative applications that need non-point source information. A feasibility test for an enhanced GIS USLE model was done in the Gisselö drainage basin before it was implemented for all river basins in the whole administrative area of Norrköpings kommun.It is possible to use the suggested simplified USLE model to estimate the load of both pollutants and sediments, and it is able to show the areas that are critical for the water quality at the outlet of the water basin. The model has been evaluated in three studies [Int. J. Geogr. Inf. Syst. 2 (4) (1988) 365; A GIS to target critical areas for non point source management, in: Proceedings of the International Non Point Source Management Symposium, Austin, TX, November 7, 1989; Vatten 48 (1992) 117]. Then, implemented in a very simple GIS that allowed only rough estimates of terrain models and distances, the model was able to estimate the total suspended solids (TSS) and total phosphorus (TP) loads in the Svartå river basin of 1539 km2 in the same region as Gisselö and the Bornsjö river basin outside Stockholm. Besides an estimated R2 of 0.91–0.98 (verified by a more than one year measurement from manual and automated sampling stations in the whole river basin), the benefit with the GIS implemented USLE was the possibility to identify the risk areas with high spatial accuracy. During the last decade, both available databases and software have changed the possibilities to identify areas at risk of nutrient leakage. Schein [GIS Methods for Monitoring Sustainable Development by Analysis of Land-use and Land Cover Changes in the Surroundings of Linköping (Sweden), Institut für Photogrammetrie und Fernerkundung, Technische Universität Dresden, Germany] and Schein and Sivertun [Method and models for sustainable development monitoring and analyses in GIS, in: Proceedings of the International Workshop on Geo-Spatial Knowledge Processing for Natural Resource Management, University of Insubria, Varese, Italy, June 28–29, 2001] show that the enhanced land use data available through the European Union agricultural support program can be used together with remote sensing data to fine tune the modified GIS USLE model. The problems with the new 50×50 m digital elevation data now available are also pointed out here. Obvious errors in the data and possibilities to enhance the model by introducing a better terrain model were two important suggestions in these works. In this article, two modifications to the original model are suggested. One is enhancement of the digital terrain model by using height curves from the digital 1:50 000 scale topographic map, and the other is a smooth distance function that better reflects the impact of nutrients on water bodies.Because of its easy implementation on standard low cost systems, the GIS USLE model is suitable for analysing huge areas for critical places. The results can lead to more detailed studies in the risk areas thus identified or to investigations on the effect of land use changes, or can be used simply for taking care in the use of fertilisers and other chemicals in the critical agricultural areas. 相似文献
228.
M. Turkyilmazoglu 《Computers & Fluids》2003,32(3):353-371
A numerical study has been undertaken to investigate the notion of absolute/convective instability in laminar incompressible trailing edge flows past wedge-like shapes with curved boundaries of the form y=α(−x)m. The effects of various trailing edge shapes m and relative thickness α on the flow separation and the development of instabilities in the vicinity of trailing edge are investigated. The nonlinear viscous-inviscid interaction equations, which have been derived by means of the asymptotic theory of flow separation, are solved first numerically to construct genuine mean velocity profiles representing the correct flow in the vicinity of the trailing edge. The absolute/convective nature of the asymptotically formed velocity profiles via a composite expansion is then ascertained by using a spatio-temporal analysis based on the Briggs-Bers pinching criterion. Although no absolute growth is encountered upstream of the trailing edge of the airfoil shapes considered, in particular the wake region behind the trailing edge of Joukowski type profiles is found to be persistently susceptible to absolute instability. It is found that separation is enhanced as the relative thickness of the airfoil gets bigger. This, in turn, is shown to lead to an additional enhancement of the absolute instability character by both increasing the absolute growth rate as well as the extent of the unstable region. Shedding frequency of the Karman vortex street is also determined behind the trailing edge shapes considered. 相似文献
229.
"数字流域"中数据共享机制研究与实现 总被引:5,自引:0,他引:5
“数字流域”是一个复杂的巨系统,“数字流域”需解决的核心问题是海量数据的共享。采用层次模型设计“数字流域”中的数据共享模型,并对其实现方法进行了详细的分析,力图为“数字流域”提供一种高效的数据共享途径。 相似文献
230.
涡流式竖井溢洪道研究述评 总被引:2,自引:0,他引:2
阮莉 《云南工业大学学报》1997,13(3):24-29
近几年国内许多单位开展了溢洪道内消能工的研究,内容包括孔板消能工、空腔消能工、阶梯消能工、同轴反向内消能工、单向涡旋内消能工等.对涡流式竖井消能工的研究也比较集中,其所具有的良好的水力特性和消能效果受到工程界的重视.传统的泄流方式在高水头、大流量、高流速运行条件下,会受到空化空蚀及流动失稳等问题的困扰,修建涡流式竖井泄洪洞是解决上述难点的有效方法之一.由于它的综合消能率在50%以上,能有效地降低洞内流速,因而选用涡流式竖井溢洪道不失为将导流洞改建成泄洪洞或单独修建泄洪洞的较佳选择. 相似文献