一种基于自适应控制器的水流调节方法

PID控制器在自动控制系统领域有广泛的应用.针对活体鱼水质监测实验中复杂多变的水样环境,提出了一种适用于活体鱼水质监测实验的PID水流调节方法.该方法利用霍尔元件进行流量探测,将获得的流速数据与活体鱼适应的流速参考值相比较,通过自适应PID控制器计算出水流流速控制量.在保证控制精度和控制速度的前提下,适应复杂非线性的水样环境,实现实时动态水流调节.     

掺气水流中气泡区域的双层动态阈值分割方法

准确地提取出掺气水流中的气泡，是利用图像测量方法进行水流特性分析的前提。由于掺气水流中的气泡是无色透明的、对比度低，而且由于实验过程的光照不均，从而给图像高精度分割带来困难。由于光照不均，致使掺气水流图像中，气泡信息强弱不均，此时又会因强信息淹没弱信息而导致气泡漏提取或提取气泡缺损，为解决此问题，提出了一种双层动态阈值的分割方法，即首先在第1层完成对气泡所在局部区域的定位，再通过贴标签处理确定出每一个气泡的局部区域；然后在第2层的精分割中，对所有局部区域进行精细分割，以实现气泡区域的精确提取。实验结果证明，该方法可以大大提高气泡提取的精度。     

A COUPLING MODEL OF WATER FLOWS AND GAS FLOWS IN EXHAUSTED GAS BUBBLE ON MISSILE LAUNCHED UNDERWATER

The gas and water flows during an underwater missile launch are numerically studied. For the gas flow, the explicit difference scheme of Non-oscillation and Non-free-parameter Dissipation (NND) is utilized to solve the Euler equations for compressible fluids in the body-fitted coordinates. For the water flow, the Hess-Smith method is employed to solve the Laplace equation for the velocity potential of irrotational water flows based on the potential theory and the boundary element method. The hybrid Eulerian-Lagrangian formulation for the free boundary conditions is used to compute the changes of the free surface of the exhausted gas bubble in time stepping. On the free surface of the exhausted gas bubble, the matched conditions of both the normal velocities and pressures are satisfied. From the numerical simulation, it is found that the exhausted gas bubble grows more rapidly in the axial direction than in the radial direction and the bubble will shrink at its "neck" finally. Numerical results of the movement of the shock wave and the distribution of the Mach number and the gas pressure within the bubble were presented, which reveals that at some time, the gas flow in the Laval nozzle is subsonic and the gas pressure in the nozzle is very high. Influences of various initial missile velocities and chamber total pressures and water depths on both the time interval when the gas flow in the nozzle is subsonic and the peak of the gas pressure at the nozzle end were discussed. It was suggested that a reasonable adjustment of the chamber total pressure can improve the performance of the engine during the underwater launch of missiles.     

Influence of Seepage Face Obliquity on Discharge of Groundwater and its Pollutant into Lake from A Typical Unconfined Aquifer

Lab experiment and mathematical simulation Modular three dimensional finite difference groundwater (MODFLOW) were performed in a soil tank to simulate the hydrogeochemical interaction between lake and typical unconfined aquifer. Results show that the velocity decreases exponentially with the transect distance on seepage face. The maximal velocity occurs at the top point of seepage face. The obliquity of seepage face has a great influence on the maximum and distribution of seepage velocity. With the increase of the obliquity of seepage face, the maximal velocity decreases quickly and the velocity distribution becomes much more even. Most of groundwater flow and pollutant flux discharges through a narrow portion near the top of seepage face. The flow and mass concentrated in the narrow portion increase with the decrease of the obliquity of seepage face. These will benefit to design a reasonable and economical scenario to manage lakeshore and to control the pollution of lake water near lakeshore.     

贺兰山东麓洪积扇含水系统特征研究

为了进一步查清贺兰山东麓洪积扇地下水系统,合理开发利用水资源,妥善处置水环境问题,采用水文地质钻探、岩土测试、物探测井、抽水试验、水化学分析、氘氧同位素分析和14C同位素测年等技术方法,对LS01钻孔进行综合勘查研究.结果表明:LS01钻孔在地表以下150 m处的上下两层水的水动力场和水化学场都具有明显的差异,显示出明...     

宋庄泵站真空破坏阀的改造及应用

宋庄泵站是引黄济青工程第2级泵站,泵站设计为堤身式结构、肘型进水流道、虹吸式出水流道、真空破坏阀断流.宋庄泵站真空破坏阀采用的是气动式真空破坏阀,其配套低压供气系统为真空破坏阀提供开阀动力.但供气系统空压机系统结构复杂,体积庞大,存在安全可靠性差、机械密封不严、漏气现象严重、工作效率低等现象,空压机补气频繁;冬季气温较...     

明渠水流阻力研究现状分析

只有正确深入地把握水流阻力规律,才能掌握解决水力学及河流动力学中各种实际问题的主动性。本文通过系统评述和研究分析前人成果,对相关问题有所澄清。历史上曾经影响较大且不需要调整参数的杜博公式、艾特魏因公式、曼宁第二公式,可反映曼宁公式所代表的平均情况,但难以像曼宁公式那样能够适应自然界复杂多变的摩阻特性。至于巴辛公式,若将其河道粗糙特征的系数与曼宁糙率系数建立关系,同样能够适用于水流阻力计算。对于动床阻力问题,众多学者已认识到水流强度、河床形态的变化及流体中含沙浓度的重要影响,也通过不同角度建立了一些经验或半经验公式。为能找出实用性强或精度高的计算公式,还必须注重分析水流、河床与泥沙运动之间相互影响的内在机理,尤其需要在各种因子的影响机理及计算途径上开展深入研究。     

较细颗粒泥沙对较粗颗粒泥沙水流挟沙力的影响试验研究

1　研究现状关于在高含沙水流输送中细颗粒泥沙对粗颗粒泥沙水流挟沙力影响的研究,前人已做了大量工作。布鲁赫和卡赞斯基[1]曾做过管道输沙试验。结果表明:在输送0.3ｍｍ的粗颗粒泥沙的管路中,加入0.01ｍｍ的细颗粒泥沙可以使水头损失显著减少、水流粘性增大、粗沙输沙能力增大,同时紊动强度显著减弱。同样的结论能不能在明渠中实现呢?即细颗粒泥沙使粗颗粒泥沙水流挟沙力增大的事实能否在明渠中成立呢?日本学者吉川和福冈曾进行过专门的试验来研究细颗粒泥沙的存在对粗颗粒泥沙输沙的影响[2]。试验在8ｍ长、0.4ｍ宽的玻璃循环水槽内进行,…     

不同坝型在不同流量下水力特性的试验研究

现代城市河流治理备受关注,除了要满足防洪排涝要求,保护河道的自然风貌,美化环境,也要符合生态的科学性原则[1],该文通过室内水槽模型试验,对城市河道修建挡水建筑物后在3种不同流量下水流特性变化进行实验研究.通过分析作者认为开口坝更有利于河道的流动水不给,且产生多级流速带,故可适应不同水生生物的生存,开口坝更利于坝体的稳...     

基于电成像资料的砂体古流向识别及应用

本文基于电成像资料及常规测井数据进行研究区的分析,利用电成像资料高纵向分辨率及有效研究砂体发育模式的优势,总结目的层岩性相的发育情况,并进一步归纳砂体古流向的判别方法。将该方法运用到区域X井后,其结果能与地质认识吻合良好,说明该方法能有效识别古流向,为勘探开发提供帮助。