水泵进水口临界淹没深度试验力学准则的研究

对影响进水口旋涡运动的主要因素进行了理论分析,研究了旋涡型式和Fr数的关系,确定了临界淹没深度试验所要求的力学准则,首次提出新的特征参数,得出了相应的临界淹没深度的计算公式。     

基于GIS栅格数据的青海省羊智沟洪水动态模拟

采用德国Gemo公司研发的Floodarea水文动力模型,基于气象和灾情资料,模拟强降水导致的山洪情景下逐小时淹没预警点的动态结果,通过淹没深度与累积雨量的拟合,有效的划分了羊智沟山洪灾害不同淹没深度下的临界雨量阈值。结果表明:1)羊智沟流域降水量呈略递减趋势,变化率为-0.02mm/年,年平均气温呈现上升趋势,变化率约为0.032℃/年。2)逐小时淹没深度与6h累积面雨量拟合关系较好,通过0.001的显著性水平检验。3)通过淹没深度和累计雨量的有效拟合,划分了羊智沟洪水临界雨量阈值,为羊智沟洪水灾害预警提供科学依据。     

U形渠道圆头量水柱水力性能影响因素研究

【目的】基于临界流原理,研究不同因素对U形渠道圆头量水柱水力性能的影响,为其在我国北方灌区的推广应用提供参考。【方法】对U形渠道上6种喉口收缩比(ε=0.75,0.70,0.63,0.56,0.50,0.44)的圆头量水柱在5种流量(Q=0.015,0.025,0.035,0.045,0.055m3/s)、4种渠道比降(i=1/1 000,1/2 000,1/3 000,1/5 000)下的测流公式、适宜喉口收缩比、水头损失、临界淹没度、测流精度等水力性能进行试验研究。【结果】圆头量水柱的驻点水深与流量间存在良好的指数相关关系,相关系数达0.997。根据试验数据回归分析得到了4种渠道比降的流量计算公式,公式符合量纲和谐原理,满足了测流精度的要求,实测流量与计算流量之间最大误差为6.79%;圆头量水柱的适宜喉口收缩比为0.50~0.70时,上游壅水高度和水头损失均较小,且临界淹没度较高,可达0.90。【结论】圆头量水柱具有结构简单、抗淤堵等优点,适合在我国北方多泥沙水源的渠道中应用。     

梯形渠道梯形喉口量水槽水力特性初探

【目的】设计一种体型简单、过流能力强的梯形渠道梯形喉口量水槽,为提高小流量时的测流精度和减小大流量时的水头损失提供支持。【方法】对梯形渠道4种喉口收缩比ε(0.427,0.506,0.557,0.681)的梯形喉口量水槽,分别在12种流量(15.39L/s,19.44L/s,23.62L/s,29.39L/s,35.91L/s,39.15L/s,45.00L/s,49.59L/s,54.28L/s,61.15L/s,65.70L/s,71.96L/s)工况下的测流精度、水头损失、临界淹没度、适宜喉口收缩比等水力性能进行试验研究,通过观测15个控制断面的水深分析水面线的变化规律及流量与收缩比、上游水深的关系,并对自由出流条件下的流量公式进行拟合。【结果】梯形喉口量水槽的上游水深与流量间存在良好的指数关系,相关系数高达0.998 6;设计梯形喉口的量水槽有效改善了梯形渠道测流的测流误差和水头损失,喉口收缩比为0.427~0.557时,实测流量与计算流量的最大相对误差为4.643%;喉口收缩比为0.506~0.681时,水头损失最大为上游总水头的12%左右,较长喉道水头损失有所减小;梯形喉口量水槽具有较高的临界淹没度,临界淹没度变化范围为0.85~0.93;综合考虑水头损失及测流精度,较适宜的喉口收缩比为0.506~0.557,喉口倾角为70°~78°。【结论】梯形喉口量水槽为灌区梯形渠道量水槽的设计提供新思路。     

球冠状凹陷对圆柱壳轴向临界载荷的影响

针对导管架受撞击后结构轴向临界载荷发生变化的问题,采用线性屈曲分析模块,模拟分析了凹陷位置、凹陷半径及深度对圆柱壳轴向临界载荷的影响,得出了球冠状凹陷对圆柱壳轴向临界载荷的影响规律。结果表明,承受轴向载荷圆柱壳对缺陷的敏感程度与凹陷位置、半径及深度有关;凹陷位置变化使得轴向临界载荷近似呈现正弦规律,凹陷半径增加使得轴向临界载荷减小,且临界载荷变化率逐渐降低;凹陷深度增加使得轴向临界载荷减小,且临界载荷变化率逐渐增加;圆柱壳对凹陷存在2个最敏感区和2个最不敏感区,这些区域不随凹陷位置、凹陷半径及深度的变化而变化;用Fourier级数拟合凹陷圆柱壳轴向临界载荷计算公式,计算值与仿真结果平均绝对误差是1.5%,满足工程分析的需要。     

干旱区盐碱地排水标准初探

探讨了气象因素、地下水矿化度、土壤质地及结构、农田灌排条件等对地下水临界深度的影响。通过试验数据制定了干旱盐碱区的地下水临界深度标准,并提出了从盐均衡角度来计算农田排水模数。     

基于GIS的洪湖分蓄洪区东分块洪水淹没损失的估算及分析

通过调查区域内乡镇及农户各类财产,对洪湖分蓄洪区东隔堤以东区域7~8月份洪水淹没的经济损失进行了估算。利用GIS/MapInfo对空间信息进行存储、统计分析和制图,结果表明,洪湖分蓄洪区在淹没深度等级为0.5 m时,历时3、69、d的经济损失分别为6.5、9.7、13.8亿元;在淹没深度等级为1.0 m时,历时3、6、9 d的经济损失分别为8.7、11.9、15.6亿元;在淹没深度等级为1.5 m时,历时3、6、9 d的经济损失分别为14.8、17.5、20.0亿元,反映出经济损失随着洪水淹没深度及历时的增长而增大的规律,在空间分布特征上表现为一致性。此结果可为分洪决策提供风险和损失评价依据。     

弧底梯形渠道无喉道量水槽水力特性的数值模拟

【目的】研究弧底梯形渠道无喉道量水渠槽的水力特性,为灌区水资源的科学管理和可持续利用提供参考依据。【方法】利用Fluent6.3大型计算流体力学软件,基于VOF方法跟踪自由液面,采用RNGk-ε湍流数学模型和PISO算法,对不同收缩比条件下的弧底梯形渠道无喉道量水槽进行三维数值模拟,分析了弧底梯形渠道无喉道量水槽内部流场以及水位流量关系,将模拟结果和实测资料对比验证,同时进一步分析了弗劳德数、临界淹没度等量水槽各项水力性能。【结果】与传统无喉道量水槽相比,弧底梯形渠道无喉道量水槽具有显著优点:(1)量水槽结构简单,过流顺畅且呈良好的流线型;(2)临界淹没度(S)可达0.89,水头损失小,弗劳德数(Fr)0.5,满足测流精度要求;(3)量水槽水位流量关系相关性较好,拟合公式测流平均误差小于5%。【结论】弧底梯形渠道无喉道量水槽结构可为灌区弧底梯形渠道量水提供新的思路和参考依据。     

跌水复氧影响因素研究

[目的]研究跌水复氧技术的影响因素。[方法]通过试验研究了跌水流量、跌水深度、跌水宽度及跌水高度对跌水复氧效果的影响。[结果]在水幕跌水状态下,复氧效果随着跌水高度增加而增加,随着跌水深度的增加而减小,随着跌水宽度的增加而增加,随着跌水流量的增加而增加。[结论]跌水的复氧效果受多因素共同影响,尤其是跌水状态对复氧效果影响较大。     

洞库油罐溢油在坑道中的流动规律

为确定机动封围设施技术参数,开展洞库油罐溢油在坑道中流动规律的研究。结合明渠非恒定流理论,建立了描述油料在洞库坑道中流动特性的物理模型,采用特征线法给出了在给定初始条件和边界条件下该模型的数值解,得到了泄漏油料在坑道中的深度及流量随泄漏时间的变化规律,同时研究了不同泄漏流量对油料流动的影响。泄漏流量越大,其在坑道中流动的流量越大,油料的深度越大,同时油料流动的距离越长;离泄漏油罐越远,不同流量下油料的深度和流量差别越小。研究成果为油库溢油机动封围设施的优化设置提供了技术支撑。     

Dynamic aggregation of chiral spinners

An object spinning at the surface of a liquid creates a chiral vortex. If the spinning object is itself chiral, its shape modifies the characteristics of the vortex; interactions between that vortex and other vortices then depend on the chirality of the objects that produce them. This paper describes the aggregation of millimeter-sized, chiral magnetized plates floating at a liquid-air interface and rotating under the influence of a rotating external magnetic field. This external field confines all the plates at densities that cause the vortices they generate to interact strongly. For one set of plates investigated, plates of one chirality attract one another, and plates of the other chirality repel other plates of both chiralities.     

A superconducting reversible rectifier that controls the motion of magnetic flux quanta

We fabricated a device that controls the motion of flux quanta in a niobium superconducting film grown on an array of nanoscale triangular pinning potentials. The controllable rectification of the vortex motion is due to the asymmetry of the fabricated magnetic pinning centers. The reversal in the direction of the vortex flow is explained by the interaction between the vortices trapped on the magnetic nanostructures and the interstitial vortices. The applied magnetic field and input current strength can tune both the polarity and magnitude of the rectified vortex flow. Our ratchet system is explained and modeled theoretically, taking the interactions between particles into consideration.     

Observation of vortex lattices in Bose-Einstein condensates

Quantized vortices play a key role in superfluidity and superconductivity. We have observed the formation of highly ordered vortex lattices in a rotating Bose-condensed gas. These triangular lattices contained over 100 vortices with lifetimes of several seconds. Individual vortices persisted up to 40 seconds. The lattices could be generated over a wide range of rotation frequencies and trap geometries, shedding light on the formation process. Our observation of dislocations, irregular structure, and dynamics indicates that gaseous Bose-Einstein condensates may be a model system for the study of vortex matter.     

Magnetic flux-line lattices and vortices in the copper oxide superconductors

A variety of recent experiments on both the static and the dynamic properties of vortices and flux-line lattices in the mixed state of the copper oxide superconductors are discussed. The experiments are of two basic types: (i) experiments that image the magnetic flux patterns either with magnetic decoration or neutrons and give information about static structures, and (ii) experiments that explore the dynamics of vortices either through the resistivity or other electrodynamic responses of the material. Results of these experiments argue in favor of the existence of a true phase transition in the high-field vortex state from a low-temperature superconducting vortex glass phase into a disordered high-temperature vortex fluid phase. The vortex glass phase transition model does a good job of explaining high-precision measurements of the dynamics at the transition. At low fields and temperatures, very long range hexatic order in the flux-line lattice is observed.     

一种芽期耐淹水稻品种的快速筛选方法及其应用

为推广适于复杂气候生态条件直播种植的耐淹水稻品种,以近年审定的部分适合江苏地区种植的粳稻品种60份为试验材料,设置两种光照处理方式,结果表明,全黑暗处理能排除了光照强度不均匀对种子萌发生长的影响.并设置2cm、3 cm和5 cm3种水深处理,分别测定3种水深处理下各品种平均芽长,结果表明,只有在5 cm水深处理下,各品种平均芽长呈明显双峰分布,且60份供试品种中仅有武粳15号、武香粳9号、武育粳18号和镇稻1号的芽长超过5.00 mm,因此明确5 cm水深处理10 d后芽长＞5.00 mm作为芽期耐淹性能强的水稻品种的筛选指标,实现了芽期耐淹水稻品种的实验室快速筛选.     

Fish exploiting vortices decrease muscle activity

Fishes moving through turbulent flows or in formation are regularly exposed to vortices. Although animals living in fluid environments commonly capture energy from vortices, experimental data on the hydrodynamics and neural control of interactions between fish and vortices are lacking. We used quantitative flow visualization and electromyography to show that trout will adopt a novel mode of locomotion to slalom in between experimentally generated vortices by activating only their anterior axial muscles. Reduced muscle activity during vortex exploitation compared with the activity of fishes engaged in undulatory swimming suggests a decrease in the cost of locomotion and provides a mechanism to understand the patterns of fish distributions in schools and riverine environments.     

野古草水淹后恢复生长动态研究

[目的]探究野古草(Arundinella anomala Steud.)水淹处理后不同恢复生长期的生长差异。[方法]通过设置对照、水淹根部(植株置于水中,仅地下部分被淹没)和水淹2 m(植株置于水中,顶部距水面2 m)3个水淹深度以及40、60、90 d 3个水淹时间,观察了野古草在出水后不同恢复生长期的生长情况。[结果]短期水淹后,野古草在整个恢复生长期的分蘖数保持不变。90 d的长期水淹后,其分蘖数在恢复生长初期迅速增加,且分蘖数增加速率都高于对照植株,在恢复生长后期生长速率有所降低,但仍高于对照植株。长时间的水淹会使野古草植株地上部分生物量减少,但在出水后的整个恢复生长期地上部分生物量会迅速增加。[结论]野古草植株在水淹后仍可进行恢复生长,长时间水淹后其生长在恢复生长初期表现更明显,说明该物种对水淹具有一定的耐受能力。     

Dynamics of Saturn's south polar vortex

The camera onboard the Cassini spacecraft has allowed us to observe many of Saturn's cloud features. We present observations of Saturn's south polar vortex (SPV) showing that it shares some properties with terrestrial hurricanes: cyclonic circulation, warm central region (the eye) surrounded by a ring of high clouds (the eye wall), and convective clouds outside the eye. The polar location and the absence of an ocean are major differences. It also shares properties with the polar vortices on Venus, such as polar location, cyclonic circulation, warm center, and long lifetime, but the Venus vortices have cold collars and are not associated with convective clouds. The SPV's combination of properties is unique among vortices in the solar system.     

水稻耐淹涝的研究进展

涝害一直是中国的主要灾害之一。概述了水稻受淹涝危害的主要表现、耐淹涝品种的特点和 耐淹涝能力评价,淹涝胁迫对水稻的影响,水稻耐淹涝生理机理及遗传改良,并对进一步开展水稻耐 淹涝研究提出了一些建议。