小浮标测流系数试验研究

流速测验的方法很多,常用的有流速仪法和浮标法,其中浮标测流法包括水面浮标法、深水浮标法、浮杆法和小浮标法等.浮标法适用于流速仪测流困难或超出流速仪测速范围的高流速、低流速、小水深等情况的流速测验.本文就小浮标测流的要求、方法及小浮标的制作进行了说明;选太原市为研究区域,对太原市六个水文站进行小浮标测流试验,并分析系数,确定出合理的、适用于各水文站的小浮标测流系数,具有很好的实用价值.     

水文缆道流速仪防水草装置简介

介绍了一种水文缆道流速仪防水草装置。该装置安装在水文缆道测流用流速仪前方，既可防止水草缠绕流速仪桨叶、确保流速仪正常工作，又不影响测流精度，具有结构简单、造价低廉、装卸方便的特点，是一种很实用的流量测验防护设施。     

巡航式ADCP系统在巴州河流水文测报中的应用研究

流量自动测验是水文现代化以及实现水文测站“无人值守、有人看管”发展理念的关键环节。本文以新疆开都河上的大山口水文站和孔雀河上的他什店水文站为试验区域,引进巡航式ADCP测流系统进行流量及流速数据测报对比试验,并与流速仪测量数据进行比测分析,综合判别巡航式ADCP测报方式的实用性。研究结果认为：巡航式ADCP测流系统能有效解决流量变化大、过程控制难以及水库坝上流量受回水顶托关系紊乱和低速测验精度低等问题,极大提升了测流效率,降低了劳动强度。从巡航式ADCP在开都河大山口和孔雀河他什店水文站中的水文测验成果看,其与流速仪测验成果高度一致,充分展示出测验精准、方便快捷的特点,完全可以作为水文资料采集的常规测流手段。研究结论为巡航式ADCP系统向巴州境内其他河流的推广应用提供了科学依据。     

试论动车积宽测流法的优越性

动车积宽测流法是“流速－面积”法流量模型积分法的一种,它的原理是流速仪沿垂直水流方向匀速移动,测定表层（或水面以下等深）水流与流速仪移动的合速度,据以推求断面平均流速,计算断面流量。指出了这种测流方法的突出特点,是改水上作业为桥上作业,保下测验安全,大幅度缩短测流历时,从而提高水文信息时效性,一套测流设备可取代多处水文站常规设备,有明显的经济效益,是开展站队结合和巡测的一种新方法。     

述評几种測定明渠瞬时流量的新方法

测定天然河流和人工渠道的瞬时流量,目前世界各国的水文測驗規范均規定以流速仪法为主,在一定条件下,也允許采用浮标法测流(包括水面浮标、深水浮标、浮杆、积深浮标等);在某种特定条件下,还可采用溶液測流法和建筑物測流法等。随着測流要求的日益提高和测速范圍的不断扩大,各国对     

ADCM测流数据后处理探索

声学多普勒剖面测流(ADCP-Acoustic Doppler Current Profilers)是当今水文领域进行流量测验的新技术.声学多普勒流速仪ADCM(ADCM-Acoustic Doppler Current Meter)用于对水文站点的流量测验,可以实现流速信息采集的自动化,但对收集到信息的后处理提出了新的要求.本文旨在探索采用自主开发程序的方式,建立声学多普勒流速仪速度、断面特性、水位等数据序列的数学模型,进而实现ADCM洲流数据快速后处理.     

流速仪法测流最小水深计算公式推导

在<河流流量测验规范>中,规定了流速仪法测流垂线、流速测点的分布位置和布置测点时的最小水深,[1]也有这方面的刊载,并列举了部分计算公式,但公式考虑不够全面,而且还不符合规范要求.本文依据规范,按流速仪测点布置情况,分析推导出了具体完整的计算公式,并对测点布置方案选择提出了相应的建议.     

GPS用于测船测流定位的探讨

为了提高流量测验的自动化水平，提高水文巡测能力，引进国际上应用广泛、技术成熟的全球卫星定位系统（GPS）来辅助流速仪法测验的定位。根据全球卫星定位系统（GPS）的工作原理，结合长江河流特性、测站特性、人力资源和水文测船等条件下的具体情况，通过野外比测试验，来探讨定位精度要求和流量测验精度等问题，提出GPS用于测流定位的精度指标。     

声学多普勒流速剖面仪应用浅析

对声学多普勒流速剖面仪在实际应用中进行了分析.通过在白山水库采用走航式及定点测流(垂向代表线法)两种方式,对白山水库测流断面进行了流量测验、流速分布及流向测量.声学多普勒流速剖面仪既适用于自由水面又适用于封冻期测量,最后对声学多普勒流速剖面仪进行了讨论.     

EKL-3A型全自动水文缆道测验系统

EKL-3A型全自动水文缆道测验系统是专为水文缆道测流研制的自动化控制系统。该系统采用工业控制计算机和PLC可编程控制器作为完成自动化缆道测流的控制核心,配合交流变频调速、光电编码测距定位、流速自动测算、音频信号传输等成熟技术和计算机测流控制软件及流量成果自动生成软件等构成。系统可通过计算机对缆道测流装置进行全自动、半自动、手动测流控制,各种测量方式均可最终生成断面流量报表和断面流速分布曲线图。     

Threshold for particle entrainment into suspension

ABSTRACT Laboratory observations regarding the limit conditions for particle entrainment into suspension are presented. A high‐speed video system was used to investigate conditions for the entrainment of sediment particles and glass beads lying over a smooth boundary as well as over a rough bed. The results extend experimental conditions of previous studies towards finer particle sizes. A criterion for the limit of entrainment into suspension is proposed which is a function of the ratio between the flow shear velocity and particle settling velocity. Observations indicate that particles totally immersed within the viscous sublayer can be entrained into suspension by the flow, which contradicts the conclusions of previous researchers. A theoretical analysis of the entrainment process within the viscous sublayer, based on force–balance considerations, is used to show that this phenomenon is related to turbulent flow events of high instantaneous values of the Reynolds stress, in agreement with previous observations. In the case of experiments with a rough bed, a hiding effect was observed, which tends to preclude the entrainment of particles finer than the roughness elements. This implies that, as the ratio between particle and roughness element sizes becomes smaller, progressively higher bed shear stresses are required to entrain particles into suspension. On the other hand, an overexposure effect was also observed, which indicates that a particle moving on a smooth bed is more prone to be entrained than the same particle moving on a bed formed by identical particles.     

Boundary layer dynamics and drag reduction in flows of high cohesive sediment suspensions

Drag reduction has been observed in suspension flows of low clay concentrations in previous studies. Here, velocity profiles and bed shear stresses, expressed as shear velocities, are measured using epoxy-coated hot-film sensors to evaluate drag reduction and controlling factors in suspension flows of high clay concentrations (4 and 8 g l^–1). The directly measured shear velocity in the viscous sublayer is found to be reduced by as much as 70% relative to the profile-derived shear velocity in the logarithmic layer. Drag reduction is found to increase with increasing clay concentration and decreasing flow strength. Density profile data indicate that the suspension flows were not stratified, and examinations of particle size distributions suggest that flocculation was not significant in causing the observed drag reduction. Measurements of the velocity profiles and of the shear velocity in the viscous sublayer indicate significant thickening of the inner wall layer and show turbulence damping in the viscous sublayer. These effects become stronger for higher concentrations and lower flow strength, suggesting that they are responsible for drag reduction in flows of clay suspension. Empirical relationships have been derived that can be used to predict the magnitude of drag reduction and the reduced shear stress in mud suspensions for both laboratory and field cohesive sediment transport studies.     

煤层气井自调偏式井口密封装置研制与试验

针对煤层气井现有井口密封装置密封效果不好,造成井口有水、气体泄漏的问题,研制了一种适用于煤层气井的自调偏式井口光杆密封装置。该密封装置从上而下依次由盘根密封盒、自调偏机构、下接头3部分组成。自调偏部分由万向节结构总成和高压挠性胶管巧妙结合,使密封盒与光杆能够始终保持随动对中。现场应用表明,该井口密封装置密封性能可靠,结构简单,具有推广应用前景。      

A field study of turbulence and sediment dynamics over subaqueous dunes with flow separation

This study examines flow, turbulence and sand suspension over large dunes in Canoe Pass, a distributary channel of the Fraser River delta, Canada. Dune morphology is characterized by a symmetrical shape and steep leeside slopes over 30°. Velocity was measured with an electromagnetic current meter and suspended sand concentration with four optical backscatter (OBS) probes. The general patterns of time-averaged velocity and sand suspension are consistent with previous studies, including an increase in mean velocity and decrease in turbulence intensity and sand concentration with height above the bed, reversed flow with high turbulence intensity and high sand concentrations in the leeside flow separation zone and an increase in near-bed velocity and sand concentration along the stoss side of the dune. Frequency spectra of near-bed velocity and OBS records from leeside separation zones are composed of two distinct frequencies, providing field confirmation of scale relations based on flume experiments. The low-frequency spectral signal probably results from wake flapping and the high-frequency signal from vortex shedding. The wake-flapping frequency predominates outside the separation zone and is linked to turbulent structures that suspend sand. Predictions from a depth-scale Strouhal Law show good agreement with measured wake-flapping frequencies. Cross-correlations of OBS records reveal that turbulent sand suspension structures advect downstream at 23–25° above the horizontal. These advection angles are similar to coherent flow structures measured in flumes and to sand suspension structures visualized over large dunes in the field.     

煤层气井有杆排采泵筒煤粉流动特征

煤层气井煤粉颗粒在有杆排采泵筒内固液两相流中的流动特征是埋泵、卡泵和凡尔漏现象的重要因素。基于泵筒中液体携煤粉的运动学和动力学分析,建立了泵筒中液体流动和煤粉运移的计算模型,并依据仿真分析得到不同排液量和煤粉粒径时,煤粉在泵筒内的运移特征。结果表明,泵筒中的煤粉运移与液体流动特征相近,煤粉运移速度正负的分界点随排液量的增大而逐渐扩大,煤粉排出量也随之不断提升。泵筒中液体携煤粉在泵筒入口附近发生湍流,并在固定阀阀孔两侧由于涡流而发生煤粉沉淀,而在泵筒内部固液两相流动则变为层流运动。两相流进泵速度较低或煤粉粒径较大时,泵入口附近开始出现煤粉沉淀,煤粉运移速度损失较小。该研究首次系统分析煤层气井泵筒内煤粉流动特征,为防煤粉有杆泵的设计及其排采作业方法提供了重要依据。      

Suspended sediment dynamics and morphodynamics in the Yellow River, China

The Yellow River in China carries large amounts of sediments in suspension at concentrations up to several hundreds of kilograms per cubic metre; the sediment is composed mainly of silt. These high sediment concentrations influence the hydrodynamics (flow velocity and turbulence) which, in turn, determine the sediment concentration profile, whereas both the high sediment concentrations and pseudo-cohesive properties of silt determine the morphodynamics of the Yellow River. The effect of sediment on the hydrodynamics is analysed using the Richardson number and the Reynolds number to provide a framework to differentiate between various flow regimes in the Yellow River, which is calibrated and validated with Yellow River data. The flow may be sub-saturated (stable flow), super-saturated (unstable flow characterized by high deposition rates, caused by collapse of turbulence), or hyperconcentrated sub-saturated (stable flow because of hindered settling effects), depending on the Richardson number. Independent of this, the flow may be turbulent, transitional or laminar, depending on the Reynolds number. Analysis of these flow types improves understanding of the flow regimes and morphodynamics of the Yellow River. The morphodynamics of the Yellow River are also affected by pseudo-cohesive behaviour caused by shear dilatance, which results in increasing critical shear stress for erosion at decreasing grain-size. This pseudo-cohesive behaviour may be partly responsible not only for the high deposition rates which characterize the lower Yellow River, but also for mass erosion during river floods.     

Frequency spectra and intermittency of the turbulent suspension process in a sand-bed river

Previous research suggests that the turbulence-driven suspension process in sand-bed channels is dominated by intermittent, energetic eddies with length scales of the order of channel depth. Because of the scarcity of data on the turbulent suspension process in alluvial channels, the possible variability in suspension intermittency and turbulent frequency content due to contrasts in flow depth, velocity or bedforms remains unclear however. The present study analyses eddy correlation suspension signals from seven deployments in varied flow conditions around a sandy meander bend. Deployment depths at near-bankfull flow stages varied from 2 to 5.5 m, velocities at 0.75–1 m height from 0.6 to 0.9 m s^?1 and local mean suspended sand concentrations ranged from 30 to 150 mg L^?1 in the intermittence and spectral content of sand suspension between the various deployments are analysed and results are compared with previously published findings. Study data suggest that the dominant eddy sizes involved in sediment mixing across the sensor level are consistently of the order of 1–5 times flow depth and lie within the ‘energy-bearing’ turbulent range. When sand suspension is analysed in the time domain in the various deployments, energetic, burst-like suspension events occupying only 1-5% of the record duration account for 20-90% of the suspension work. The degree of intermittence in the suspension process was observed to increase in deeper flows, where mixing events contributing extreme vertical sediment fluxes appear to be relatively more frequent.     

虚拟垂线流速时差法流量计算方法研究

根据目前传统时差法流量计算存在的问题,提出并着重阐述了虚拟垂线流速时差法流量计流量计算方法。在京杭大运河徐州段运河水文站进行了计算验证。结果表明,虚拟垂线时差法与传统时差法和流速仪法趋势一致,虚拟垂线法优于传统时差法。可为工程技术人员提供参考,为国产化时差测流装置提供技术支撑。     

基于Ls-Dyna的高能射流式冲击器活塞杆回程应力分析

针对在钻探实践中高能射流式冲击器的活塞杆频繁出现尾部塑性变形严重影响冲击器工作性能和整体寿命的现象,拟对活塞杆进行优化改进。利用非线性动力学仿真软件Ls-Dyna对活塞杆的回程撞击缸体进行数值模拟和优化分析,并进行了室内试验,结果表明：冲击末速度为4 m/s,活塞杆回程撞击缸体强制停止运动瞬间,尾部产生的应力集中值为3 339.28 MPa,导致其破坏;优化改进后,活塞杆上下端直径比为17/16、尾部圆弧直径为60 mm,活塞杆体内的应力集中值为1 419.66 MPa,较改进前活塞杆的应力集中值减小58%。试验验证表明,优化后的活塞能大幅提高使用寿命和耐久性。     

粘性泥石流的平均运动速度研究

粘性泥石流是泥石流类型中最常见也是危害最大的类型,泥石流的运动速度是泥石流的动力学参数中最重要的参数,因此准确而简洁地计算粘性泥石流的运动速度就显得非常重要。不同的泥石流地区的泥石流阻力有很大的不同:有的地区阻力较大,属于高阻力地区,泥石流运动速度较低;有的地区阻力较小,属于低阻力地区,泥石流运动速度较高。目前的粘性泥石流平均速度公式还不能兼顾计算所有地区的不同阻力类型的泥石流速度。泥石流的不均匀系数在不同的泥石流地区有很大的不同：不均匀系数小的地区阻力大,而不均匀系数大的地区阻力小,因此可以用不均匀系数划分泥石流沟的阻力特征,从而得到能兼顾所有不同地区的泥石流阻力规律。由一系列野外观测资料得到的由泥石流不均匀系数、泥石流运动底部纵比降和水力半径计算的粘性泥石流运动平均速度经验公式,能适应各种类型的泥石流沟,与其它系列的观测资料对比有很好的一致性,与粘性泥流的观测资料对比也很接近。由流体流动的福劳德数可以确定流动的缓急程度。一般的粘性泥石流都是急流,少数是缓流,极少数是运动速度非常缓慢的容重过大的粘性泥石流。粘性泥石流运动平均速度经验公式用于一般急流的粘性泥石流的速度计算结果很好,但不适用于容重过大的缓慢流动,对于缓流粘性泥石流速度计算偏大。在对泥石流的评估和治理中,平均速度公式可以用于泥石流堆积扇上游渠道中的粘性泥石流速度计算,对泥石流堆积扇上的粘性泥石流速度计算偏大,不适用于缓慢流动粘性泥石流,但在对泥石流的危害评估和治理中可以忽略缓慢流动的发生。