河道流速仪法测验垂线流速分布参数1/n对Ⅱ型误差的影响

在山区的窄深河道断面上按<河流流量测验规范>要求制定测流方案时,可能会遇到断面概化垂线流速分布形式参数1/n11值超越<河流流量测验规范>"Ⅱ型误差表"或"地区综合Ⅱ误差表"中1/n11的取值范围,在这种情况下为了正确引用Ⅱ型误差表中的数据,需分析1/n值对Ⅱ型误差的影响程度以及变化趋势.     

ADCP非实测区流速推算软件的设计与实现

ADCP广泛应用于河流流量测验,但其在断面流量测验过程中存在着非实测区,这给需要这些区域流速的实际应用带来了不便.根据已有文献关于明渠垂线流速分布的报道,结合ADCP操作软件(WinRiver)的说明书,在介绍其非实测区流速推算方法的基础上,设计并用Visual Basic实现了一款ADCP非实测区流速推算软件,以满足实际应用的需要.     

蜗壳断面形状对泵径向力平衡影响的研究与探讨北大核心

本文对采用梯形断面、圆形断面、矩形断面的3种不同断面形状的单蜗壳泵和多蜗壳泵内部流场进行CFD数值模拟分析,研究其径向力的平衡。研究表明,断面形状对泵的径向力及扬程、效率有一定的影响。在小流量工况点时,单蜗壳泵采用圆形断面,多蜗壳泵采用矩形断面径向力较小;在设计流量工况点时,不同断面的多蜗壳泵径向力较单蜗壳泵大;在大流量工况点时,单蜗壳泵采用矩形断面,多蜗壳泵采用梯形断面径向力较好。研究结论对双蜗壳泵的设计和实际生产都有一定的指导意义。     

走航式ADCP在澜沧江流量测验中的应用

通过走航式ADCP在澜沧江流量测验的实际应用,阐述了ADCP流量测量的过程及特点,明确了其适用环境以及测验使用条件.对走航式ADCP与常规缆道流速仪法测得的流量比测,验证了ADCP的测流精度,相比具有更高的测验效率,省工省时.说明ADCP测流系统技术先进,功能齐全、性能稳定、安全可靠、安装方便,数据采集自动化程度较高,在测量现场能直接地获取各类测流数据,满足澜沧江流量测验,为ADCP在云南及西南河流流量测验的推广应用抛砖引玉.     

平板闸门淹没出流流量的实验研究

搭建了一个水力学的实验模型,并对平板闸孔淹没出流的流量进行了实验,利用理论分析方法分析了平板闸门在淹没出流的流态下的流量计算公式,得出了淹没出流流量值主要与流量系数有关。为了对其流量系数进行研究分析,以常用的3种淹没出流流量系数的计算公式计算出流量,将计算得出的3种理论流量值分别与实验测得的流量值进行对比,得出了最优的计算方法,为工程应用中淹没流量系数计算公式的选择提供了实验依据。     

基于PumpLinx的余热排出泵汽蚀余量的仿真方法研究

阐述了汽蚀的原理与现象,提出了一种对核电厂用正常余热排出泵进行汽蚀余量仿真研究的数值模拟方法。对水力模型流体区域进行建模,并介绍了模型假设和简化、网格的生成方法、工作介质的物性以及数值模拟仿真计算方法。按ANSI/HI1.6离心泵试验要求进行仿真,通过对各流量点不同进口压力的扬程数据进行拟合计算,获得设计流量点、小流量点和大流量点扬程下降3%时的汽蚀余量NPSH3值。     

BTA深孔钻喉部结构的数值优化研究

针对深孔切削加工进行时,排屑效率低与钻头喉部易堵屑的问题,对BTA冷却系统冷却液出口断面速度,以及冷却液在钻头喉部的流动过程与特性进行了研究,基于计算流体动力学(CFD)与射流卷吸效应,提出了一种新型的BTA深孔钻头喉部结构。对加工时的压强和流量参数进行了分析后,修订了有限元冷却液模型的湍流强度和耗散速率,在此基础上进行了两种钻头喉部结构的排屑能力对比试验,测量了冷却液系统的冷却液出口断面流出平均速度。研究结果表明:实验时,新型喉部结构的直径38 mm BTA深孔钻头所组成的冷却系统,其冷却液出口断面流出的平均速度提高12.6%;同时,冷却液系统整体的排屑能力也得到了提高。     

超声波流量计在复杂流道中应用的试验研究

针对南水北调工程淮安第三抽水站现场测试中流量测量存在的困难,对其流道进行模型试验.通过CFD数值计算对流道模型进行简化.提出超声波流量计在不规则流道中新的安装应用方式,通过模型试验,确定新的安装方式下各声路的计算权重,以及流量计算所需的平均断面面积,得出该安装方式下流量计算公式,为现场测量提供充足的依据,同时也为其它复杂流道的流量测量提供一种新的方法和借鉴.     

高压磨料水射流切割玻璃纤维增强塑料的试验研究

对玻璃纤维增强塑料的水射流切割工艺进行了试验研究。分析了进给速度、压力、磨料流量、靶距4个主要工艺参数对切割效率、切割断面粗糙度、切缝宽度和断面斜度的影响关系。通过极差分析法确定了最优的工艺参数组合;借用Matlab编程软件对正交试验数据进行非线性多元回归分析,得到磨料水射流切割效率和切割断面粗糙度的工艺参数经验模型。     

基于粒子群解耦算法的 FBG 流量温度复合传感研究

针对光纤布拉格光栅流量温度复合传感解耦困难的问题,提出了一种基于粒子群解耦算法的光纤布拉格光栅流量温度复合传感器。首先,结合光纤布拉格光栅传感理论和流量温度复合传感理论,研究了基于光纤布拉格光栅的流量温度复合传感机理。然后,设计了悬臂梁为空心圆柱的一体靶式结构的光纤布拉格光栅流量温度复合传感器,搭建了流量温度实验系统平台,进行了温度和流量复合传感实验。最后,提出了一种基于粒子群算法的FBG流量温度复合传感解耦方法,并运用所设计的粒子群算法对实验数据进行流量与温度解耦研究。研究结果表明,解耦后传感器在3～8 m~3/h的范围内其流量最大误差为0.014 m~3/h,温度最大误差为0.021℃,流量测量误差为0.28%,温度测量误差为1.5%,流量均方误差为1.16×10^-4 m~3/h,温度均方误差为1.53×10^-4℃,与神经网络算法进行性能比较后,结果表明所采用的粒子群算法解耦效果良好,有效地提高了传感器的测量精度。     

Prediction of stage–discharge curves in open-channels using a fixed-point velocity measurement

The single-point measurement method for discharge estimation, which was first introduced by Maghrebi, can be implemented to obtain the discharge at different stages of a river during a flood event. As an advantage of this method, discharge can be estimated automatically with a fixed measurement location in the river section or on the water surface, which is associated with minimum energy and cost consumptions. For the proposed model, we determine the isovel contours in a normalized form for the cross section of the flow. To do so, we need to apply the field or experimental data, concerning the cross sectional geometry at different stages and its roughness variation along the wetted perimeter to the model. Then we collect the data of the single fixed-point of velocity measurement at the flow section using a velocity current meter. To validate the method, it is applied to a flume with different cases of roughened walls. The obtained results of stage–discharge curves using the single point of measurement in comparison to the observed experimental ones show that this method can quickly and accurately estimate the flood discharges. The maximum deviation between the observed and calculated discharges for most of observations is less than 5%.     

Application of large scale PIV in river surface turbulence measurements and water depth estimation

Large-Scale Particle Image Velocimetry (LSPIV) has emerged as a reliable technology to measure river surface flow velocity distribution and can be applied to estimate river discharge. Fewer studies have explored the capability of surface turbulence measurements using LSPIV. In this paper, LSPIV is applied to evaluate statistics of surface turbulence of a natural river. Turbulence measurements including velocity fluctuation, velocity spectra and the dissipation rate of turbulent kinetic energy (TKE) are validated by comparing with those measured by an Acoustic Doppler Velocimeter (ADV). Traditionally, estimation of stream discharge through LSPIV needs a secondary measurement to determine river bathymetry and water depth. A new method is presented here to demonstrate that for a fully developed and channel-controlled flow, the cross section geometry can be estimated from the combined measurements of surface mean velocity and the dissipation rate, following the Manning-Strickler formula. Therefore, river discharge can be estimated with LSPIV along with a calibrated Manning's roughness, without additional bathymetry survey. The proposed new method is applied to measure discharge in Milwaukee River (Milwaukee, Wisconsin, U.S.A.), which agreed well with data obtained from a nearby streamgage station.     

基于泵送压力的混凝土泵排量计量方法

分析现有混凝土泵排量计量方法的特点,指出现有计量方法在计量精度方面的不足.根据混凝土泵工作原理建立混凝土泵排量数学模型,指出计量混凝土泵排量的关键是实时泵送效率系数.分析影响实时泵送效率系数的因素以及混凝土缸压力与主液压缸压力之间的关系,提出基于泵送压力的计量方法.通过直接测量混凝土泵主油缸压力,分析主油缸压力变化趋势,计算实时泵送效率系数,对混凝土泵实际排量进行计量.试验表明,所提方法具有较高计量精度.     

Measuring river velocity and discharge with acoustic Doppler profilers

Acoustic Doppler profilers and associated software packages presently are being used to measure water velocity, channel bathymetry, and river discharge. The instruments have various configurations and frequencies; choice of the appropriate instrument depends on various factors including depth, width, and sediment load of the rivers being measured. The acoustic Doppler profilers are mounted on powerboats or small remote-controlled or tethered rafts or catamarans. Profilers enable users to make fast, accurate, and economical discharge measurements on large rivers and rivers with unsteady flow conditions because of flooding or irregular releases from reservoirs. This article describes the principles of operation, application of acoustic Doppler profilers to the measurement of velocity and discharge, and calibration and verification issues.     

Discharge estimation for submerged parallel radial gates

Seven hundred ninety-seven field-measured data points were collected to calibrate multiple parallel radial gates. Data were collected from three control structures (i.e., Al-Tawfiki, Al-Menoufi, and Abasi regulators), which are located in the Delta irrigation district of Egypt. Upstream and downstream water depths, gate opening size, and flow discharge was measured at each structure. Additionally, previous calibration methods were reviewed and evaluated. Dimensional analysis with application of the incomplete self-similarity concept demonstrated the best results for the study area. Based on the field measurement data, a simple formula that implicitly considers the discharge coefficient is proposed for estimating the flow rate through submerged parallel radial gates.     

Experiences in discharge measurements at Small Hydropower Stations in India

As a part of Ministry of New and Renewable Energy (MNRE), Government of India programme for promoting small hydropower (shp) development, efficiency testing and performance evaluation of Small Hydro Power plants is mandatory for receiving financial incentives by plant developer. The task of efficiency testing and performance evaluation of shp plants was assigned by MNRE to Alternate hydro Energy Centre (AHEC) Indian Institute of Technology Roorkee in the year 2003 along with financial support to acquire the required instrumentation and develop expertise. Over 200 small hydro plants (SHPs) of different capacity (1–25 MW) as well as types viz dam toe based, run of river and canal fall based have been tested for efficiency and performance evaluation during the period 2005–2018 in different states of India as per IEC-60041, IEC-62006, ISO -1438-1 and ISO-748 to the extend feasible as per available resources and time. During efficiency testing of hydro plants, it has been found that discharge measurement is very challenging activity as the most of the plant owners did not provide the required space and provisions for mounting/fixing the instruments for discharge measurement. After commissioning of the plants it becomes extremely difficult to select the ideal/suitable locations and providing the provisions for mounting different measuring instruments. Various problems observed during discharge measurement are discussed in this paper and may be helpful for testing in future.     

伺服阀滑阀叠合量测量方法

阐述了伺服阀滑阀叠合量间接、气动综合和液动综合测量法的原理和数学模型,分析了它们的优缺点和应用情况.针对流量系数变化影响液动流量式综合测量法精度的问题,提出了根据阀口流态进行补偿的方法,以提高叠合量的液动测量精度.     

Non-contact flood discharge measurements using an X-band pulse radar (II) Improvements and applications

This paper presents and applies an improved method of determining cross-sectional depth and discharge of a river. The method used with the universal law and Darcy-Weisbach friction factors to obtain the lateral variation of the roughness height. This method of measurement was successfully used at the Kaoping River during the Xangsane typhoon in Taiwan, and the results show that the surface velocity obtained using an X-band pulse radar system were close to that obtained by the float method. The estimated discharges at four stages were within 3% of the recorded values of the stage-discharge rating curve in the gauging station.     

Estimation of one-dimensional velocity distribution by measuring velocity at two points

The measurement of the velocity distribution and discharge in the open channels has always been an important issue in hydraulics. Unfortunately, flow measurement in the open channel is often expensive and sometimes produces poor results. There are many empirical methods to estimate the velocity distribution in a conduit, however, these methods are often applicable only to a narrow range of open channel conditions. In this paper, considering velocity as a random parameter, one-dimensional velocity distribution in open-channel has been derived based on the entropy concept and the principle of maximum entropy (POME). The entropy indexes (M, G, λ₂ and λ_*) are important parameters in entropy method to estimate velocity distribution and discharge in a conduit. A new approach is presented in this work for estimating the entropy parameters based on two-point velocity measurements. The approach for estimating the entropy parameters is tested for laboratory observations and velocity distribution and discharge are determined using Shannon, Renyi and Tsallis entropy methods. The present approach has shown good agreement with measured data. Also, the results showed that Tsallis entropy method is more accurate than other forms of entropy and the calculated values of NRMSE for estimated velocity profile and discharge are 7.86 and 8.8% respectively, showing a good simulation.     

A method for correcting discharge of boat-mounted ADCP measurements

GPS data are usually used to measure boat velocity during boat-mounted acoustic Doppler current profiler (ADCP) measurements when bottom tracking is biased by moving bed. GPS cannot provide consistently accurate boat velocity reference because of multipath errors, satellite signal reception problems, and heading errors. In addition, the computation of water velocity from an ADCP mounted onto a moving boat is a vector-algebra problem, thus the discharge calculation is subject to the compass error when GPS is used for boat velocity reference. This paper proposes a method for correcting discharge based on the idea that the discharge calculation is independent of the boat path. The processing of two sets of boat-mounted ADCP measurements integrated with differential GPS and non-differential GPS was simulated to verify the method. The results show that the proposed method performs well in both differential and non-differential GPS conditions. The relative errors range from 0.1% to 1.5% for all measurements with the mean relative errors of 0.7%. Analytical assessment of the GPS errors shows the proposed method is insensitive to the positioning accuracy of GPS, but positioning error of non-differential GPS may induce relative discharge error of more than 1% when the river or stream is narrow. On the contrary, a relatively small compass or heading error can cause a significant error in water velocity and discharge when using GPS as the boat velocity reference. Therefore, integrating a differential GPS and maintaining a slow boat speed are best practices for discharge measurement, especially for narrow streams or short boat paths.