二维岩体裂隙网络有压渗流数值模拟分析

根据裂隙岩体的渗流机理对岩体裂隙网络中的渗流进行了合理简化和假设,以渗流立方定理、质量守恒定理和水流不可压缩假设为基础建立了裂隙网络的有压渗流模型,用改进DDA算法得到了裂隙几何信息,并用PCG算法和可视化编程技术开发了相应的计算程序.通过与Grenoble试验对比,验证了程序的合理性.对DECOVALEX项目的二维BMT模型进行了初步渗流计算,获得了均匀和非均匀裂隙条件下不同的渗流规律.该结果为研究岩石裂隙网络的应力-渗流耦合效应奠定了基础.     

渗流影响下坝体和岩基应力场的分析模型研究

用等效面力和体力代替渗流影响下引起的湿胀效应的计算表达式,提出了数值分析法模拟湿胀效应的加载方法．此外,还提出了考虑坝体湿胀影响下的坝基应力场与渗流场的耦合分析模型,研制了相应的有限元分析程序．由实例分析了不同方法计算渗流影响时对岩基稳定的效应,并得出了在考虑应力场与渗流场耦合作用下,其计算成果更接近实际的结论．     

DDA中裂隙岩体渗流网络识别方法的改进及应用

裂隙网络是岩体渗流的主要通道,对其进行准确高效的识别是实现基于DDA的渗流应力耦合方法的重要步骤。通过建立环块体裂隙排列数组,以裂隙为搜索路径,提出更简单、效率更高的节点识别方法;同时提出外边界、边界节点及外边界角点的识别方法,构建出包括以上要素的完整裂隙网络,使外水压力荷载能有效施加在块体系统上,扩展DDA裂隙网络识别方法的适用性。将此方法应用于基于DDA的渗流应力耦合模型,并结合算例进行考虑渗流应力耦合的数值计算。结果表明,该方法可准确识别出复杂裂隙网络,可结合基于DDA的渗流应力耦合程序完成模拟计算。研究成果为裂隙岩体在渗流状态下的失稳判断提供了依据。     

深切河谷边坡裂隙岩体渗透性与埋深的关系

河谷区边坡裂隙岩体的渗透性分布规律,对于边坡渗流分析的参数选取有着重要的参考意义。通过分析单一裂隙的渗流规律及河谷地区边坡应力分布特征,研究了在复杂应力条件下及存在边坡卸荷作用时河谷边坡裂隙岩体渗透性随岩体埋深的分布规律,并结合白鹤滩水电站坝址区玄武岩岸坡岩体钻孔压水试验资料,采用表征裂隙岩体渗透性的单位吸水量ω为参数,通过统计分析验证了理论推导的结果。     

基于无单元法的应力场与渗流场耦合分析模型

应用迭代解耦技术建立了基于无单元法的应力场与渗流场耦合分析计算模型并研制开发了计算程序。以矩形坝为例,计算比较了有无耦合作用时的坝体应力场和渗流场。结果表明,耦合作用时坝体的位移略小但分布规律一致;坝体的水平正应力分布差别较大,垂直正应力、剪应力和等势线变化较大,但分布规律一致。计算结果符合一般规律,用无单元法进行应力场和渗流场耦合分析是可行的。     

裂隙网络渗流理论的软硬互层状岩体渗流分析

为研究软硬互层状岩体的渗透规律,根据层状岩体中的裂隙发育规律,把互层状岩体简化为由层面裂隙和构造裂隙组成的离散裂隙介质,建立了互层状岩体渗流离散裂隙网络模型,并根据裂隙交叉处的流量守恒原理求解其渗流场。通过一个算例验证了模型的合理性,并讨论了切层裂隙开度对垂直方向渗流的影响,得到了互层状岩体渗透场的分布特点。     

岩体单裂隙辐射流水力耦合试验研究

通过构造具有不同几何特征的裂隙，综合考虑粗糙度、法向压力、剪切位移的影响，研究了单裂隙辐射流条件的剪切渗流耦合特性。结果发现不同裂隙的渗流量和渗透系数随剪切位移变化明显，且法向压力的作用也随剪切位移增加而改变；对于表面轻微破坏的裂隙，初始剪切位移会增加裂隙渗透性，随后达到基本稳定，但裂隙一旦发生严重破坏并生成较多填充物，进一步剪切将会减小裂隙渗透性及导致其随剪切位移波动；对于生成大量填充物的裂隙，由于较高的水压会引起填充物在裂隙内重分布，从而封堵渗流路径，减少渗流量；在强耦合过程中裂隙渗透性随剪切位移的变化很难用一个统一关系表达式来描述，但粗糙度和法向压力的影响均与不同剪切阶段呈很强的关联性。     

裂隙岩体平面非稳定渗流模型

以单条平直裂隙中的水流运动规律为基础,构建二维裂隙网络非稳定渗流模型。利用算例在多种工况下的计算结果绘制岩体内部渗流水头等值线,并对不同工况下的渗流水头等值线进行合理比较,以获得水库水位变化与坝址岩体渗流场之间的关系以及水位变化后岩体内部水头与边界水头之间的关系。     

变开度的岩体裂隙网络非稳定渗流数值分析

根据裂隙的几何特性所服从的分布特征,利用Monte-Carlo方法模拟岩体裂隙网络分布以及裂隙张开度.基于裂隙岩体网络非稳定渗流数学模型,编制程序并通过工程算例进行分析比较.结果表明：运用Monte-Carlo方法模拟岩体裂隙网络分布状况是比较好的方法;变开度时岩体裂隙渗流有明显的偏流效应现象,裂隙变开度时其滞后效应比等开度时更加明显;在变开度条件下,当上下游水头差较大时,水头分布变化受张开度的影响较大,不宜忽略,当上下游水头差较小时,影响非常小可以忽略.     

基于LHS法的三维随机裂隙网络数值模拟及渗流分析

为分析裂隙渗流系数的影响因素,基于拉丁超立方抽样(LHS)法,对岩体内裂隙的几何参数进行抽样模拟,提出了一种改进三维随机裂隙网络生成算法。利用C++语言编制程序,实现三维裂隙网络的生成,通过与Monte Carlo法生成的三维裂隙网络进行对比分析,验证了LHS法生成的三维裂隙网络稳定性好、精度高,为解决Monte Carlo法抽样样本坍塌问题提供了一种新思路。并基于LHS法生成三维裂隙网络,借助离散裂隙网络渗流程序进行渗流分析。结果表明,裂隙岩体的渗透系数随裂隙尺寸及裂隙密度的增加而增加,当裂隙尺寸及裂隙密度达到一定量级时,裂隙岩体内会形成贯通的裂隙簇,裂隙岩体渗透系数将急剧增加。     

火电厂节能工作浅析

本文探讨了火电厂节能基本程序和工作方法,分析节能工作要从基础工作、技术创新、设备整治、燃烧管理等方面入手的论述.     

浅析磨合期汽车的使用

如何合理使用磨合期的汽车，使其摩擦机件的磨损量能够平稳、均匀地磨合而不至于过度磨损，对汽车实际使用寿命有着重要的意义。从机器磨合期的特点和磨损机理出发，对汽车磨合期如何正确使用进行了有实际意义的探讨。     

Geothermal energy in agriculture in Yugoslavia

SFR Yugoslavia has natural hot water springs practically all over its territory, indicating the presence of geothermal reservoirs underground. There is no final estimate of how much energy can be expected from this new resource, except for figures based on the results of studies and investigations.The first use of geothermal energy in Yugoslavia in numerous spas dates back to the 19th century. Some remarkable examples of central heating are known, but the most widespread use is in agriculture (in greenhouse heating, farm heating and drying of agricultural products).     

Energy conservation measures in an institutional building in sub-tropical climate in Australia

In this study, various energy conservation measures (ECMs) on heating, ventilating and air conditioning (HVAC) and lighting systems for a four-storied institutional building in sub-tropical (hot and humid climate) Queensland, Australia are evaluated using the simulation software called DesignBuilder (DB). Base case scenario of energy consumption profiles of existing systems are analysed and simulated first then, the simulated results are verified by on-site measured data. Three categories of ECMs, namely major investment ECMs (variable air volume (VAV) systems against constant air volume (CAV); and low coefficient of performance (COP) chillers against high COP chillers); minor investment ECMs (photo electric dimming control system against general lighting, and double glazed low emittance windows against single-glazed windows) and zero investment ECMs (reset heating and cooling set point temperatures) are evaluated. It is found that the building considered in this study can save up to 41.87% energy without compromising occupancies thermal comfort by implementing the above mentioned ECMs into the existing system.     

Uncertainties in decarbonising heat in the UK

Heating is arguably one of the most difficult sectors to decarbonise in the UK's energy system. Meeting the 80% greenhouse gas emission reduction target by 2050 is likely to require that heat related emissions of CO₂ from buildings are near zero by 2050, and there is a 70% reduction in emissions from industry (from 1990 levels). Though it is clear that the use of the natural gas network will reduce over time, recent modelling suggests a limited residual role for gas by 2050 to help meet peaks in heat demand. High levels of uncertainty about the way in which heat will be decarbonised present a number of challenges to policy makers. This paper will explore the risks and uncertainties associated with the transition to a low carbon heat system in the UK as outlined by the 4th carbon budget review. The potential impact of key uncertainties on the levelised costs of heat technologies and the development of energy networks are explored using a sensitivity analysis approach. Policy changes required to decarbonise the heat sector are also examined.     

Solar drying in sludge management in Turkey

Two main wastewater treatment plants in Bursa city in Turkey will start to operate and produce at least 27,000 tons of dry solids per year by the end of 2006. The purpose of this study was to investigate an economical solution to the sludge management problem that Bursa city would encounter. The general trend in Turkey is mechanical dewatering to obtain a dry solid (DS) content of 20%, and liming the mechanically dewatered sludge to reach the legal landfilling requirement, 35% DS content. This study recommends limited liming & solar drying as an alternative to only-liming the mechanically dewatered sludge. Open and covered solar sludge drying plants were constructed in pilot scale for experimental purposes. Dry solids and climatic conditions were constantly measured. Faecal coliform reduction was also monitored. The specially designed covered solar drying plant proved to be more efficient than the open plant in terms of drying and faecal coliform reduction. It was found that, if the limited liming & solar drying method was applied after mechanical dewatering instead of only-liming method, the total amount of the sludge to be disposed would be reduced by approximately 40%. This would lead to a reduction in the transportation, handling, and landfilling costs. The covered drying system would amortize itself in 4 years.     

Viscous heating in liquid flows in micro-channels

Many experimental works on forced convection through micro-channels evidenced that when the hydraulic diameter is less than 1 mm, conventional theory can no longer be considered as suitable to predict the pressure drop and convective heat transfer coefficients. This conclusion seemed valid for both gas and liquid flows. Sometimes the authors justified this claim by invoking “new” micro-effects. On the contrary, in this paper the explanation of the experimental results obtained for micro-channels in terms of friction factors will be researched inside the conventional theory (Navier-Stokes equations). In particular, this paper will focus on the role of viscous heating in fluids flowing through micro-channels. A criterion will be presented to draw the limit of significance for viscous dissipation effects in micro-channel flows. The role of the cross-sectional geometry on viscous dissipation will be highlighted and the minimum Reynolds number for which viscous dissipation effects can no longer be neglected will be calculated as a function of the hydraulic diameter and of the micro-channel geometry for different fluids. It will be demonstrated how viscous effects can explain some experimental results on the Poiseuille numbers in micro-channels, which recently appeared in the open literature.     

Energy consumption in rural transportation in India

Energy consumption in rural transportation has been computed, taking into account the energy embodied in vehicles or bullocks, as well as the fuels or feeds and food (of operators). Bullock cart transport consumes over four times more energy than vehicles. However, animal transport will continue to be preferred because of its availability.     

Electoral cycles in electricity losses in India

A third of electricity in India is lost each year, where losses refer to power that is supplied but not billed. Utilizing data from the power corporation of Uttar Pradesh, India's most populous state, we study the politics of electricity losses. Examining annual data over four decades, we document that UP's electricity losses tend to increase in periods immediately prior to state assembly elections. Drawing upon geographically disaggregated data for the period 2000–09, we observe higher line losses just prior to the 2002 and 2007 state elections. Our analysis shows that the incumbent party was more likely to retain the assembly seat as line losses in the locality increased. We interpret these results as corroboration that political parties deliberately redirect electricity to flat rate and unbilled users in a context of chronically inadequate supply. Political factors appear to affect line losses in ways that technical and economic factors alone cannot explain.