Shallow Turbulent Flows by Video Imaging Method

Shallow turbulent flows were produced in a tank of small thickness to study the friction effects on large-scale turbulent motion of small depth. The tank was constructed of two parallel walls. The space between the parallel walls (4.4, 1.57, and 0.59 cm) was small compared with the height (107 cm) and the width (212 cm) of the tank, and was varied during the experiments for different friction effects. Turbulent flows were produced by the injection of water in the form of starting jets into the tank filled with water. The large-scale turbulent flow in the small space between the walls of the tank is confined to essentially two-dimensional motion, and the motion is retarded by the force of friction. Dye was injected with the source fluid as the tracer for the highly unsteady and quasitwo-dimensional turbulent motion. From the initiation of the turbulent motion at the source to the final interaction of the jets with the tank bottom, the entire sequence of events was recorded by a pair of video cameras. The depth-averaged concentration of the dye was analyzed using the recorded video images.     

A Finite Element Computational Method for Gas Hydrate. Part I: Theory

A finite element scheme is presented to model the dissociation of gas hydrates in porous media by hot water injection. We show a complete derivation of the finite element formulation, including the associated mass and energy conservation equations capable of performing transient analysis of both conductive and convective heat transfer for gas and liquid flow in porous media. The scheme also includes the latent heat effect to accommodate the change of phase due to melting of hydrate. In the companion paper, Part II, this method is successfully applied to hydrate reservoirs.     

Mixing Center of a Channel

For longitudinally uniform stretches of waterways there is a mixing center for the across-channel location of a steady point source in steady flow, such that complete mixing is achieved as soon as possible and there is no concentration overshoot at either of the two shorelines. A mathematical definition of the mixing center is the zero of the first oscillatory cross-channel diffusion mode. With the shorelines plus four interior data points across the channel, the starting estimate for the mixing center suffices to keep peak shoreline concentrations to within 6% of optimal. For comparison, a source at mid flow gives 18% shoreline concentration overshoot in the test case. Should very high precision be required, the Appendix gives an iterative construction that converges to the first oscillatory diffusion mode.     

地下水运动数值模拟过程中边界条件问题探讨

本文对地下水运动数值模拟过程中边界条件的涵义 和处理方法进行了分析和讨论。阐述了边界条件所包含的双重意义。指出随着人类活动影响 强度的日益增大，边界条件的处理要面临一些新的更为复杂的问题。在模型预报之前必须首 先对边界条件做出预报。边界条件的预报既要考虑自然因素的作用，同时也要考虑人类活动 (人工开采和人工补给)的影响及由于邻区水流条件变化而产生的耦合效应。之后，给出了两 个应用实例。     

云南东川泥石流沟与非泥石流沟~(137)Cs示踪法物源研究

运用1 37Cs示踪法调查云南东川小江流域 6条泥石流沟、6条非泥石流沟和主河的泥沙来源。泥沙主要来源于冲沟侵蚀和滑坡崩塌堆积、坡耕地和草地。坡耕地和草地表层土壤1 37Cs平均含量分别为 0 9Bq m2 和1 98Bq m2 ,冲沟沟壁和滑坡崩塌堆积土体1 37Cs。作者通过 3种源地土体1 37Cs含量的比较 ,分析了细粒泥沙(<0 0 1mm)的来源。 6条泥石流沟冲沟侵蚀和重力侵蚀 (滑坡崩塌 )的相对产沙量变化于 90 2 %～ 1 0 0 % ,平均值为 95 1 % ,6条非泥石流沟的相对产沙量变化于 74 5 %～ 83 3% ,平均值为 78 9%。小江主河为 81 4 %。     

Uncertainty of Predictions of Embankment Dam Breach Parameters

Risk assessment studies considering the failure of embankment dams often require the prediction of basic geometric and temporal parameters of a breach, or the estimation of peak breach outflows. Many of the relations most commonly used to make these predictions were developed from statistical analyses of data collected from historic dam failures. The prediction uncertainties of these methods are widely recognized to be very large, but have never been specifically quantified. This paper presents an analysis of the uncertainty of many of these breach parameter and peak flow prediction methods. Application of the methods and the uncertainty analysis are illustrated through a case study of a risk assessment recently performed by the Bureau of Reclamation for a large embankment dam in North Dakota.     

双层堤基的井涌破坏与无害管涌

双层堤基水文地质结构特殊，堤基承压水常具独特的“渗而不流”特征。在“不流”条件下，堤后盖层薄弱处受超高承压水头顶裂破坏，产生的局部冒水孔实属承压自流井，由此形成的管涌实质为井涌。底部进水的承压井流影响范围不大，井涌的破坏范围更小，据此可区分出有害管涌与无害管涌。前者局限于堤脚附近，小范围压渗为首选方案；对后者，既无需专门防治，更不必追求根治。     

安塞低渗油田孔隙结构对渗流特征曲线的影响

渗流曲线的测定是认识油藏流体渗流规律的基础。实验发现安塞油田储集层岩心渗流曲线在低有效净围压下近似表现为两段直线，通过压汞实验和毛管压力曲线数据分析，认为这种特征与储集层孔隙结构有关。在分析渗流特征时应综合考虑孔隙结核特征、流体与孔隙介质的相互作用等因素。     

青海省桥头电厂河子沟灰场拦洪坝粘滞流模型试验分析

本文采用粘滞流模型试验对青海桥头电厂河子沟灰场拦洪坝设计方案进行了论证，分析了多种防渗条件下的渗流场特点，提出了满足工程运作的既经济又合理的建议。