水下滑翔机水动力性能分析及滑翔姿态优化研究

水下滑翔机是一种新型的无人运载器,具有低阻力、长航程、长续航力特点,其独特的设计显示出了极大的优势。文中采用数值模拟方法计算了不同速度不同攻角情况下水下滑翔机的阻力、升力及对于浮心的俯仰力矩,对其周围流场水动力学性能进行了分析,并通过流场的流动结构研究了受力随滑翔姿态变化的规律。从做功的角度提出了滑翔姿态的优化目标函数,得出水下滑翔机模型高效滑翔姿态角的控制规律。     

HYDRODYNAMIC AND ELASTOHYDRODYNAMIC STUDIES OF A CYLINDRICAL JOURNAL BEARING

In this article, the effect of the bearing elastic deformation on the performance characteristics of a cylindrical journal bearing is analyzed. The variety of simulation models covers hydrodynamic (HD) and elastohydrodynamic (EHD) lubrication theories. The Reynolds equations governing the flow in the clearance space of the journal bearing are obtained by considering the effect of mass transfer across the fluid film. The finite element method with an iteration scheme was employed to solve both the Reynolds equation and the three-dimensional elasticity equation representing the displacement field in the bearing shell. The converged solutions for the lubricant flow and elastic deformation vector are obtained. Dynamic characteristics of the journal bearing are computed for HD and EHD theories. Numerical simulation results show that the flexibility of bearing liner has a significant influence on the performance of a cylindrical journal bearing. Indeed, the elastic deformations of the bearing liner extend the pressure area in the bearing and increase the minimum film thickness. Although, dynamic coefficient, load capacity and attitude angle decrease.     

The thermal variability of the waters of Fathom Five National Marine Park,Lake Huron

Measurements of the thermal stratification at 3 locations within Fathom Five National Marine Park in Lake Huron, Ontario during the summers of 2006 and 2007 found large oscillations in the position of the thermocline. These oscillations led to considerable variability in the temperature at a given depth, with frequent changes in temperature at a rate of 5 °C per hour, and brief periods where temperatures changed at the rate of 10 °C per hour. The thermal stress due to such fast rates of temperature change has been previously implicated in negative effects on many aquatic organisms. The thermocline was observed to move by as much as 20 m vertically, and had dominant periods of oscillation of 12, 17 and 24 h. The strongest temperature variability occurs in the depth range of 10–20 m, which accounts for 20% of the total lakebed area within Fathom Five. The temperature variability was lowest in deep regions well below the thermocline and at a sheltered area behind a reef. This variability was a ubiquitous feature of the water column of Fathom Five during the summer stratification, and the impact of these frequent short-term thermal fluctuations on benthic and fish habitat is discussed in this note.     

Three dimensional modeling of the effects of changes in meteorological forcing on the thermal structure of Lake Erie

A three dimensional hydrodynamic model, the Estuary and Lake Computer Model (ELCOM), validated by field data collected in 2008, is used to investigate the thermal structure response in Lake Erie to changes in air temperature and wind speed. We define spatially and temporally varying regions for the epilimnion, thermocline, and hypolimnion. Increasing the air temperature warms up the epilimnion but has little effect on the hypolimnion. The stratification forms earlier and breaks down later. The thermocline is raised modestly in the warmer air temperature scenario. Stronger winds cool the epilimnion slightly, but warm up the hypolimnion with much larger temperature changes. The stratification duration is shortened, and the thermocline depth is noticeably deepened. Due to the large differences in depths and layer thicknesses of the three basins, the responses to changes in meteorological forcing vary among the basin. Exploiting the power of the three dimensional model to provide a more authentic characterization of thermal stratification in large lakes, it is shown that patterns inferred from simple isotherm dynamics when studying the stratification period as typically done with one dimensional models are not always accurate. The present results for Lake Erie show the potential for complicated and interactive effects of climate forcing on important biogeochemical processes, especially hypolimnetic oxygen depletion.     

河谷坡度对高面板堆石坝应力变形特征的影响

以玛尔挡水电站面板坝工程为例,建立了不同河谷坡度方案下的面板坝三维有限元模型,研究不同河谷坡度下高面板堆石坝坝体的静动位移和应力分布情况,分析了河谷坡度对坝体应力变形特征的影响,探讨了地震工况下河谷坡度对坝体结构稳定性的影响。结果表明:河谷坡度为50°时堆石体内部将会出现较明显的应力拱效应现象,河谷边坡陡缓临界值近似为50°;坝体沉降与坡度变化之间呈负相关关系;地震作用未对拱效应存在下的坝体产生显著的不利影响。     

Factors influencing thermal structure in a tributary bay of Three Gorges Reservoir

To better understand the factors influencing the thermal structure of tributaries in the Three Gorges Reservoir(TGR),a well validated three-dimensional hydrodynamic and water temperature model was proposed to simulate the water temperature distribution in the Xiangxi Bay, a representative tributary of TGR.The numerical results show that water temperature stratification seasonally occurred in the Xiangxi Bay, with stable vertical temperature profiles.It is found from the numerical experiments that three key factors are responsible for the formation of water temperature structure:(1) very often,the locations of thermocline are mainly determined by wind speeds, and the higher the wind speed is, the deeper the thermocline is located beneath the water surface,which could be expressed by a fitted exponential function,(2) the thermal structure is affected by static stability of water column, and the thermocline becomes closer to the water surface and its thickness increases with the increase of temperature, (3) due to the effect of the thermal density inflow, the water temperature of the hypolimnion tends to be uniform, however, even under the condition of larger inflow discharge,the influence of the inflow on the epilimnion and the thermocline is not significant.     

NUMERICAL SIMULATION OF FLOW AND HEAT TRANSFER CHARA-CTERISTICS OUTSIDE A PERIODICALLY VIBRATING TUBE

Fluid flow and heat transfer characteristics outside a vibrating tube were numerically simulated by the dynamic mesh method. The mechanism of heat transfer enhancement via periodic vibration of the tube was explored by using the field synergy principle. It is found that the field synergy angle between fluid velocity vector and temperature gradient vector for a periodically vibrating tube is significantly smaller than that for a stationary tube, and it changes approximately according to the sinusoidal law in a vibration period. The effect of time phase of the vibration on the field synergy angle and convective heat transfer coefficient were also discussed. Results indicate that the vibration can enhance heat transfer and this effect is more remarkable when time phase angle ranges between 50° and 1400 in a half period. Especially when the time phase angle is 90°, the average field synergy angle outside the tube reaches the minimum, which leads to the best heat transfer performance.     

控制幕作用下水库温流场特征初步研究

大型水库建成后由于库区水动力学特性、光混特性、热量特性等发生了改变,水库垂向水温将呈现出明显的分层现象,对库区及其下游河道的生态环境造成显著影响,常通过采用分层取水措施加以改善。针对控制幕分层取水方法,通过温分层水槽试验,研究了分层水体中设置水温控制幕后,控制幕前水温、流速分布特征以及下泄水温的变化情况。试验考虑了不同热冷水流量比、控制幕距取水口距离、取水口位置和控制幕遮挡率等因素的影响。试验结果表明:控制幕设置后,控制幕上游近幕布区域温跃层厚度减小,温跃层强度增大,水体掺混受到抑制;控制幕下游温跃层厚度增大明显,控制幕促进了控制幕下游水体的垂向扩散,破坏了原水体分层现象;控制幕上游近幕布区域,热冷水流量比越小取水口位置越低,控制幕遮挡率越小温跃层厚度越厚,温跃层强度越小。热冷水流量比增大,取水口位置提高以及控制幕遮挡率增加均会使下泄水温升高。     

FLUID DYNAMIC PERFORMANCE OF GROOVED PLANING BOAT AND ITS EFFECT ON RESISTANCE

NOMENCLATUREφ———stress tensor of fluid n———unit vector of inner normal onSsurfaceRf———frictional resistanceRr———residuary resistanceα———angle of attack(°)Fτ———resultant force of viscosity tangencystressL———hydrodynamic liftU———speed of uniformity incoming flowV———speed of hull surfaceLp———length of chine projectedVg———speed of groove top surfacenZ→———unit vector projection of outer normalalong axesZonSsurfaceZ0———highness of water surface(Z)…     

Effects of Selective Withdrawal on Hydrodynamics of a Stratified Reservoir

In water supply reservoirs, selective withdrawal is commonly implemented to control released water temperature for quality purposes. This study investigated the effects of selective withdrawal on hydrodynamics of a stratified reservoir through numerical modeling and analytical analysis. A 3-D hydrodynamic model was applied where observations of water temperature time series recorded every 30 min at the thermocline and measured temperature profiles along the water column were used to validate the numerical model. The effect of selective withdrawal from four outlets located along the water intake structure of Tahtali Reservoir in Turkey on water temperatures was investigated and the effects on thermal stratification structure were discussed. Withdrawal of the water at the bottom outlet was found to be the most effective choice encouraging the mixing of the water column and thus reducing anoxia. The results of this study can be used to guide the further investigations in stratified lakes for better management practices.     

Hydrodynamic analyses of typical underwater gliders

The underwater glider changes its weight and the weight distribution through the battery use, to move up and down and forward in the sea. It enjoys many advantages such as a long endurance, and a long operational range with its unique device. The performance of the underwater glider can not evaluated only by the drag, the energy consumption is also one of the key factors. In this paper, the power conversion ratio is proposed according to the transfer efficiency from the gravitational potential energy to the available work, and the performances of three typical underwater gliders are evaluated from multi-angles, such as the drag, the power conversion ratio and the barycenter's offset. So the glide performance and the energy consumption in various motion states can be analyzed. The results of this paper can provide a theoretical basis for further study of underwater gliders.     

洪家渡水电站大坝垂直和水平位移计的布置与安装

洪家渡水电站大坝垂直、水平位移计布置时采用二、三维有限元动静力应力应变分析，并与已建大坝工程观测成果相对比，布置了11条横向垂直，水平位移计，1条纵向垂直、水平位移计，由于对施工干扰影响大，洪家渡水电站大坝横向垂直，水平位移计采用了“堆埋法”进行安装，结果比较成功，文中介绍了其工艺流程，操作及实施效果。     

SALT-FINGERING OF POLLUTANT VERTICAL MIXING IN STATIC THERMAL-STRATIFIED WATER

Pollutant vertical mixing in stratified waters is a key factor that affects the vertical pollutant distribution in deep thermal-stratified reservoirs.This article presents an experimental study of the vertical mixing in thermal-stratified waters and an analysis of the retarded tracer jet diffusion in the thermocline layer.In the experiment,Reynolds number rapidly decreases from 104 to 10 1 .The stronger the stratification,the more seriously retarded the mixing will be.Some small tracer blobs may penetrate the thermocline layer into the hypolimnion layer even the main tracer cloud is retarded.According to its appearance,it can remain with salt-fingering,where the blobs are isolated away from the main cloud and mixed with the surround cold water in the hypolimnion layer.Therefore,the vertical distribution of the tracer under the thermocline layer would take larger values than expected.According to measurements,the isolated blob contents are accounted for about 5%-20%of the main tracer cloud,and are decreased with the increase of the stratification intensity.Results also show that the stronger the stratification,the smaller finger width would be.The averaged width of the incipient fingers is proportional to-0.3272 power of the temperature gradient,ΔT/Δz,or-0.2823 power of the thermal Rayleigh number,T Ra,in the turbulent jet fluid.     

青铜峡水电站河西导墙变位计监测数据计算方法

结合青铜峡水电站河西导墙3条变位计的布设情况,推导和论证了变位计的水平和顺渠向位移公式,并对其中的水平面线体转角和铟钢线温度影响进行了分析,认为两者对水平位移和顺渠向位移的影响很小,可以在资料分析中予以忽略.该研究弥补了河西导墙变位计监测资料分析存在的欠缺,为正确掌握导墙的变形规律提供了计算手段.     

某幼儿园隔震结构设计与抗震性能分析

为了研究采用隔震技术的框架结构抗震性能,对隔震层位于地下室柱顶的某三层框架结构进 行有限元数值模拟和动力时程分析。综合考虑隔震装置的布置、隔震支座的尺寸选取以及下部独立柱 结构的加强等因素进行设计。分析结果表明:相比于非隔震结构,隔震结构在设防烈度7度（0．15ｇ）中 震作用下,上部结构层间剪力减震率均超过63％,上部结构最大位移角为1／503;在超烈度8度（0．20ｇ） 大震作用下,上部结构最大位移角为1／401,下部独立柱结构位移角1／3070,隔震层水平位移为限值的 68．９％,上部各楼层加速度减震率也达到61．4％以上。工程设计与分析表明:在设防烈度中震作用下, 隔震结构比抗震结构的周期延长4．02倍,减震效果显著,说明了较规则结构可以很好地发挥隔震技术 优势;经过不断地设计优化,并进行超烈度地震作用的验算和论证,表明了隔震工程具备抵抗超烈度地 震作用的能力（提高了1度）,可以提高整体结构的抗震性能。     

Vertical oscillations of the thermocline caused by internal waves modify coldwater pelagic fish distribution: Results from a large stratified lake

Fishes typically occupy a species-specific temperature range, with their occupied depth being related to the lake’s temperature profile. When a fish’s preferred temperature range coincides with the thermocline, the location of their preferred thermal habitat is influenced by the rise and fall of internal waves, leading to possible changes in fish depth. These internal waves are common in large, stratified lakes, yet we do not know how they affect the spatial distribution and behavior of freshwater fishes. We conducted nighttime hydroacoustic surveys in a large, deep embayment of a large thermally stratified lake to observe whether pelagic fish respond to vertical oscillations of the thermocline caused by internal waves. The coldwater pelagic fish in our study (primarily cisco, Coregonus artedi) typically occupied a narrow vertical band approximately 5–8 m thick and temperatures between 10.8 ± 0.8–13.6 ± 1.6 °C (fishes sized 106–500 mm), just below the thermocline (centered around 15–17 °C). Importantly, the upper bound of fish depth varied in response to vertical thermocline movements associated with internal waves, suggesting fish respond to changes in their physical environment on timescales commensurate with basin-scale internal wave periods (hours to days), to remain within their preferred thermal habitat. Dissolved-oxygen levels were typically above avoidance thresholds of these fish, thus not likely exerting a strong influence on fish location. Our findings emphasize the need to account for internal waves when designing hydroacoustic and netting surveys, as thermocline movements can influence where fish are located.     

考虑爆破累积损伤效应的含泥化夹层边坡滑移分析

反复爆破振动是诱发滑坡的重要因素,特别是含泥化夹层的复杂岩质边坡。为揭示多次爆破振动下含泥化夹层复杂岩质边坡失稳破坏机制,根据能量守恒定律,基于Newmark滑块位移法,考虑爆破累积损伤效应,引入泥化夹层强度折减系数,建立了多次爆破振动下含泥化夹层边坡累积滑移量计算和临界爆破振动次数预测方法。探讨了剪切模量、倾角和连续率等泥化夹层参数对多次爆破振动下边坡累积滑移量的影响,并对泥化夹层参数敏感性进行了分析。研究结果表明:（1）考虑爆破累积损伤效应引起的泥化夹层强度参数劣化,边坡累积滑移量计算和临界爆破振动次数预测结果更加合理。（2）泥化夹层参数对多次爆破振动下边坡累积滑移量具有显著影响。随泥化夹层剪切模量的增大,边坡抵抗变形能力增大,累积滑移量减小。随泥化夹层倾角的增大,边坡剪切段滑移量无明显变化,但蠕滑段滑移量明显增大,总的累积滑移量随之增大。泥化夹层连续率越高,边坡累积滑移量越大。（3）参数敏感性分析表明,泥化夹层剪切模量对多次爆破振动下边坡累积滑移量影响最显著,其次是泥化夹层倾角,再次是泥化夹层连续率。     

大坝裂缝及接缝监测设计与监测方法

大坝裂缝及接缝监测对于了解坝的工作性态和整体性，分析其产生的原因和对大坝安全的影响，以便必要时进行有效的处理都是非常重要的。文章对与此有关的技术问题进行了探讨。     

茅坪滑坡体位移特征及其发展趋势预测

 茅坪滑坡体是清江库区一个十分典型和重要的滑坡体，１９９３年雨季和水库蓄水以来，滑坡体位移日趋明显，表现为具有整体滑移特征。本文通过建立滑坡体不同时段位移的ＧＭ（１，１）灰色模型，对位移变化趋势作了分析，结果表明，位移模型拟合精度高，预测成果达到了中、短期预报的目的，对清江隔河岩水利工程的建设与管理具有重要的参考价值。     

公路泥质砂岩边坡预警判据与参数敏感性分析

针对高速公路边坡,以Ⅴ级强风化泥质粉砂岩边坡为研究对象,采用有限元强度折减法,分析边坡的变形与应力应变特点,确定地表测点处的位移临界阈值与变形演化规律,为灾害前兆的识别提供依据。建立变形与安全系数的相关关系,结合现场安全监测与边坡表征现象进行判别,共同建立相应预警判据的综合安全监控体系。同时,考虑因素的主效应与相互间的交互作用,采用均匀设计试验分析了影响边坡稳定性的敏感性因子黏聚力c、内摩擦角φ、重度γ、坡度α与稳定性的变化关系,强度参数与滑动面的变化规律,以及开挖方式与级别的影响,揭示了各参数的内在联系及其对边坡稳定性贡献率的分异特征。结果表明:非线性回归分析能较好地拟合出稳定性系数F与参数间的二次多项式函数关系,影响因素中材料因素大于几何因素,人工开挖方式与开挖级别的影响较小,滑动面随c和φ的变化规律相反,边坡失稳前存在位移的3阶段演化进程。