A novel ensemble model for predicting the performance of a novel vertical slot fishway

We investigate the performance of a novel vertical slot fishway by employing finite volume and surrogate models. Multiple linear regression, multiple log equation regression, gene expression programming, and combinations of these models are employed to predict the maximum turbulence, maximum velocity, resting area, and water depth of the middle pool in the fishway. The statistical parameters and error terms, including the coefficient of determination, root mean square error, normalized square error, maximum positive and negative errors, and mean absolute percentage error were employed to evaluate and compare the accuracy of the models. We also conducted a parametric study. The independent variables include the opening between baffles (OBB), the ratio of the length of the large and small baffles, the volume flow rate, and the angle of the large baffle. The results show that the key parameters of the maximum turbulence and velocity are the volume flow rate and OBB.     

GPS与声学多普勒流速剖面仪在"动底"测流中的应用研究

在高水期和含沙量较大的情况下,用声学多普勒流速剖面仪ADCP(Acoustic Dopppler Current Profilers)在进行底跟踪测量时会发生偏差.本文引入全球定位系统的定位技术,将两者有机地结合起来,并进行GPS跟踪方式的方向改正,用于"动底"长江流量测验,降低ADCP的底跟踪模式下的测量偏差.     

A composite indicator for water meter replacement in an urban distribution network

In water supply management, volumetric water meter are typically used to measure users' consumption. With water meters, utilities can collect useful data for billing, assess the water balance of the system, and identify failures in the network, water theft and anomalous user behaviour. Despite their importance, these instruments are characterised by intrinsic errors that cause so-called apparent losses. The complexity of the physical phenomena associated with metering errors in aging water meters does not allow meter replacement to be guided by single parameters, such as the meter age or the total volume passed through the meter. This paper presents a meter replacement strategy based on a composite ‘Replacement Indicator’ (RI) that aims to reduce apparent losses. The performance of a meter during its operating life was analysed by means of this indicator, which signals when the meter needs to be replaced. To test the reliability and robustness of the proposed indicator, a Monte Carlo uncertainty analysis was performed. The methodology was applied to a real case study: a district metered area (DMA) in the Palermo city water distribution network (Italy). The analysis showed that ranking based on the composite indicator is better than common ranking procedures based on typical variables (e.g., the meter error curve or the meter age): the proposed indicator can better select the meters to be replaced and favourably affect the associated costs.     

Analysis of the influence of range and angle of incidence of terrestrial laser scanning measurements on tunnel inspection

Terrestrial Laser Scanner (TLS) measurements are subject to errors which influence the quality of the 3D models built from the point clouds. In this paper, a methodology to build an error model of the TLS measurements is proposed. Measurement errors are estimated based on two of the factors that mostly affect their magnitude: distance to the object and angle of incidence.The error model is used to analyze, by means of Monte Carlo simulation, the spatial distribution of the errors in a point cloud of a circular tunnel section and also to simulate the effect of the measurement error in tunnel inspection works.The results obtained indicate that although the angle of incidence influences the point cloud quality when the laser is located near the tunnel gable, its effect is counteracted by the point density when a surface is fitted to the point cloud.     

Online energy-based error indicator for the assessment of numerical and experimental errors in a hybrid simulation

Hybrid simulation is an effective structural test technique combining the numerical simulation of substructures with predictable behavior, and experimental testing of complex components that are difficult to model. Consequently, hybrid simulation is prone to both numerical and experimental errors. In this paper, the dominant sources of numerical and experimental errors that can contaminate the results of a hybrid simulation are examined. It is shown that linearized analytical stability and accuracy limits for algorithms and test procedures used in a hybrid simulation may fail to adequately predict the results due to errors and nonlinearities of actual tests. An alternative approach based on monitoring the energy balance of the structural system is proposed to capture the effects of both experimental and numerical errors. This method extends an existing experimental error indicator to also account for (a) errors resulting from modification of experimental measurements by iterative corrections in numerical integrators or other signal correction procedures, and (b) numerical errors in the integration algorithm including equilibrium errors and kinematic relations between displacement, velocity and acceleration. The effectiveness of the proposed energy error indicator in predicting severity of errors is demonstrated through numerical and experimental simulations using various integration procedures.     

Processes driving the episodic flux of faecal indicator organisms in streams impacting on recreational and shellfish harvesting waters

Understanding the process controls on episodic fluxes of faecal indicator organisms (FIOs) is becoming increasingly important for the sustainable management and accurate modelling of water quality in both recreational and shellfish harvesting waters. Both environments exhibit transitory non-compliance with microbiological standards after rainfall episodes despite significant expenditures on control of sewage derived pollutant loadings in recent years. This paper demonstrates the role of wave propagation in the entrainment of FIOs from river channel beds as a contributor to episodes of poor microbial water quality. Previously reported data is reviewed in the light of relationships between wave and mean water travel velocities. High flows and rapid changes in river flow, driven by releases of bacterially pure reservoir water, resulted in elevated FIO concentrations and transient peaks in concentration. The new interpretation of these data suggest three modes of entrainment: (i) immediate wave-front disturbance, (ii) wave propagation lift and post-wave transport at mean flow velocity, and (iii) stochastic erosional mechanisms that maintain elevated bacterial concentrations under steady high flow conditions. This is a significant advance on the previously proposed mechanisms. Understanding these mechanisms provides an aid to managing streams intended for recreational use and emphasises the need to control the timing of high flow generation prior to use of the water body for e.g. canoeing events. In addition the processes highlighted have relevance for the protection of shellfish nurseries, drinking water supply intakes and episodes of poor bathing water quality, and associated health risks.     

基于DBL理论的隧道排水管岩溶水结晶规律研究

针对岩溶区隧道排水管结晶堵塞问题,在DBL理论的基础上结合水动力学,分别讨论了层流、紊流两种流态下的流速分布并推导出结晶沉淀速率函数表达式;采用模型试验的方法对岩溶水结晶规律进行探讨,以管道铺设坡度和液面高度为变量,将结晶厚度增长速率作为结晶沉淀速率分析指标,结果显示:随着管道铺设坡度的增大,结晶厚度增长速率逐渐减小,随着管道液面高度的增大,结晶厚度增长速率逐渐减小。此外,对比理论与试验的结果发现管道铺设坡度为3%、4%、5%时,相对误差分别为11.54%、10.14%、11.29%;管道液面高度为7.2 mm、10.2 mm、13.3 mm时,相对误差分别为11.29%、15.87%、15.09%,因此在误差允许的范围内,可认为结晶沉淀速率函数预测模型得到了有效的验证。     

能量的局部误差估计和直接积分法的时步自适应算法

本文研究了直接积分法中时间离散引起的位移和速度局部误差，区分了动力系统的能量，能量的局部误差和位移、速度局部误差的能量三者的关系。提出将系统能量的局部误差作为后验误差估计指标。该误差估计指标的物理意义明确，不仅考虑了位移局部误差而且还考虑了速度局部误差对能量局部误差的影响。本文还给出了相应的时间步长自适应调节算法，并在算例中实现了时间步长的自适调节计算，同时验证了本文误差估计的精确性和可靠性     

水源热泵回灌困难颗粒阻塞试验研究

 以水源热泵回灌过程中物理堵塞现象作为研究对象,利用玻璃珠和砾石颗粒作为多孔介质,以碱性氧化铝作为悬浮颗粒,利用自行研制的砂层阻塞试验系统装置模拟多孔介质中悬浮颗粒的迁移和沉积过程,试验中介质运动速度控制在20～200 cm/min。研究悬浮颗粒在玻璃珠和砾石颗粒中沉积时水压力与流速关系,对悬浮颗粒在2种不同介质中的沉积机制进行分析;同时研究玻璃珠介质在相同的流速和不同的悬浮颗粒浓度下相对渗透率与时间的变化关系;最后给出渗透系数衰减模型,模型对预见渗透系数的降低是有效的。     

流体流速对超声波流量计在线比对相对误差的影响

超声波流量计在供水计量中存在着较大的相对误差。本文通过多次24h测试分析误差与流速的关系及产生原因,提出流速变化较大的计量点应采取24h累计流量或多点流速比对法消除流量计相对误差的方法。     

Characterization of two-phase flow in a single rock joint

An experimental study using a triaxial apparatus was used to analyze the two-phase flow patterns in jointed rock specimens. Rock specimens having a single natural fracture were tested for two-phase flow of water and air. Triaxial tests were conducted to characterize the two-phase flow through fractured granite specimens at low confining pressures. It was found that for a relatively smooth joint (JRC<6), bubble flow pattern occurred within the rock joint when the gas velocity is below 15 m/s. The average velocity of water usually varied between 0.1 and 0.5 m/s for bubble flow patterns. In this velocity range, air bubbles were able to form along the joint walls or to be randomly displaced within the water phase. When the gas velocity inside the rock joint exceeded 22 m/s, the flow patterns took annular form for non-zero capillary pressures (i.e., injected gas pressure is not equal to injected water pressure). At elevated (>0.25 MPa) gas injection pressures, the gas occupied the main part of the fracture and the liquid was able to flow as an unstable film forming an annular flow along the joint. When the annular flow developed, the mixture flow pattern was independent of the air flow velocity. This was due to the fact that once the injected air velocity reached a critical value (i.e., 20 m/s), water velocity inside the joint was negligible for a given confining pressure and injected water pressure. Further increase in inlet air pressures developed a single-phase air flow with no water flow.     

含水层参数识别的M on te-Carlo 方法

 采用Monte2Carlo 随机模拟方法模拟观测数据, 根据水头和流量观测数据识别含水层的导水系数。通过对经典最小二乘法目标函数的修正, 添加了流量残差平方和最小一项, 保证参数识别结果的唯一性。研究表明, 当观测误差为正态分布时, 参数识别结果也为正态分布。采用本文所提出的含水层参数识别方法, 即使水头观测标准差达到1m , 参数识别结果的平均值与理论值的相对误差小于1%。     

景观水体的水动力优化设计

城市景观水体通常水流不畅，水质难以维持，需要外加机械动力促使水体循环流动。以河网流速〉0．25m／s和驱动装置整体流量最小为控制目标，利用MIKE11软件对上海某景观河网进行了水动力模拟，对驱动装置的安装位置、数量及流量进行方案组合，通过大量试算提出了驱动装置的合理位置及经济流量。实测表明，模拟结果误差在可接受范围内，为工程设计提供了理论指导。     

Optimal sensor locations for contamination detection in pressure-deficient water distribution networks using genetic algorithm

A new sensor placement problem is formulated to cover two objectives of: (1) assuring quality of water delivered to consumers; and (2) detection of any contamination event at the earliest so as to minimize its consequences, through maximization of: (1) demand coverage; and (2) time-constrained detection likelihood for pressure deficient networks. The network may become pressure-deficient owing to continued use of water distribution network beyond its design life. The two objectives are combined using weights. Genetic algorithm is used to obtain optimum sensor locations. The methodology is applied to a pressure- deficient network in the Dharampeth zone of Nagpur city (India). The pressure- dependent analysis is carried out using WaterGem v8i to simulate the system hydraulics. Performance objectives are evaluated considering the availability of flows at nodes and velocity of flow in pipes under pressure-deficient conditions. Comparison of optimal sensor network design is carried out with that obtained by demand-dependent analysis.     

Modeling of bare and aspirated thermocouples in compartment fires

As part of an effort to characterize the uncertainties associated with temperature measurements in fire environments, models of bare bead, single-shielded aspirated, and double-shielded aspirated thermocouples were developed and used to study the effects of varying the gas and average effective surroundings temperatures on the thermocouple error of each configuration. The models were developed for steady-state conditions and hence provide information about error trends rather than about absolute error values. The models indicate that thermocouples respond differently to changes in effective surroundings temperature in a hot upper-layer than in a relatively cooler lower layer of a room fire. In an upper-layer, for a given gas temperature, the thermocouple error is relatively insensitive to surroundings temperature. In a lower layer, errors which increase rapidly with surroundings temperature are possible. The most extreme errors occur in a lower layer when the gas temperature is low and the surroundings temperature is high. Aspirated thermocouples reduce the errors in both the upper and lower layers of a room fire, but do not eliminate them entirely. The present study is intended to provide fire researchers with a methodology for developing working models of thermocouples which are tailored to their own configurations.     

Accounting for Losses: The Bursts and Background Concept

Losses of treated water occur through leakage and overflows from the pressurized pipes and fittings in water undertakers'distribution systems and customers'private supply pipes. The UK National Leakage Control Initiative was formed in 1991 to update previous published work on leakage control policy and practice in the UK.
Although some published technical relationships exist, there has been no overall methodology which attempts to provide a component-based estimate of annual losses in different parts of the distribution system for any particular combination of local circumstances, i.e. pressure, burst frequency, burst flow rate, number of properties, length of mains, method of leakage control, standards of service, and waste notice service/enforcement policy.
The 'bursts and background estimate'spreadsheet-based methodology is designed to provide such estimates. It links 'night-flow'and 'annual losses'concepts, and can be used for a variety of purposes. These include (a) assessment of the likely incidence of losses for different leakage control and waste notice policies, (b) identification (from night flows) of districts in which there are unreported bursts, and (c) assessment of economic target levels for leakage control. The substantial element of annual losses from service pipes, and the considerable influence of pressure on annual losses, are also discussed.     

Estimating flow rates through individual outlets of siphonic roof drainage systems

An experimental investigation is used to quantify the flow rates through individual outlets of multi-outlet siphonic roof drainage systems under both full-pipe and partially filled pipe flow conditions. A pressure transducer and a propeller-type current meter were installed within each tailpipe to measure water depth and flow velocity. The study tests the hypothesis that it may be possible to predict accurately the flow rates through individual outlets of multi-outlet siphonic roof drainage systems. A new technique of estimating flow rates is trialled by comparing instantaneous pressure transducer and current meter readings with previously calibrated flow data to find the best data match. The study results were very positive and clearly demonstrate that the underlying methodology was appropriate and that it may be possible to model numerically the individual outlet flow rates in multi-outlet siphonic roof drainage systems.     

A role for human reliability analysis (HRA) in preventing drinking water incidents and securing safe drinking water

The prevalence of water quality incidents and disease outbreaks suggests an imperative to analyse and understand the roles of operators and organisations in the water supply system. One means considered in this paper is through human reliability analysis (HRA). We classify the human errors contributing to 62 drinking water accidents occurring in affluent countries from 1974 to 2001; define the lifecycle of these incidents; and adapt Reason's ‘Swiss cheese’ model for drinking water safety. We discuss the role of HRA in human error reduction and drinking water safety and propose a future research agenda for human error reduction in the water sector.     

Experimental characterization of various scale hydraulic signatures in a flooded branched street network

ABSTRACT

Understanding urban flood flow repartition mechanisms within street network remains challenging. This paper presents an experimental dataset of water depth and velocity profiles in the Icube experimental rig. The spatial variability of discharge along a street is highlighted. Comparing the water depth gradient orientation and the flow repartition promotes for complex repartition mechanisms at small scales. Comparable unit-discharge values are observed in both large and narrow streets. Interestingly, the intensity of the discharge deviation at the crossroad scale is related with the asymmetry of the velocity profile entering a crossroad. Moreover, discharges at the crossroad and the subdistrict scales show that downscaling of the flow repartition relationship is difficult. At real scale, results show that inflow velocity profile asymmetry may persist on a distance of several street widths downstream of a crossroad. Such distances are insufficient to consider disconnected crossroads as done in the literature to establish discharge repartition relationships.     

Sewer Discharge Estimation by Stereoscopic Imaging and Synchronized Frame Processing

A system for fully automatic contact‐less image‐based measurement of volumetric flow rate in urban drainage structures is presented. The hardware includes two original equipment manufacturer cameras and a single‐board computer on which our custom image processing software is running. The value of water discharge depends on the surface velocity, water level and channel's geometry. The level of the flow is estimated as the difference between distances from the camera to the water surface and from the camera to the channel's bottom. Camera‐to‐water distance is recovered automatically using large‐scale stereo‐matching, whereas the distance to the channel's bottom is measured upon installation. Surface velocity is calculated using cross‐correlation template matching: individual natural particles in the flow are detected and tracked throughout the sequence of images recorded over a fixed time interval. The relative discharge computation error is lower than 1.34% of the theoretical maximal discharge for a given location, which makes our system competitive to commercial components such as ultrasonic flow meters, while using cheaper technologies.