多声路时差式超声波流量计在大型压力钢管与大型箱涵上的安装应用

通过典型例子简单的分析了多声路时差式超声波流量计在大型压力钢管及混凝土箱涵上从换能器选型、安装断面的选择、声路布置及安装方法等方面的不同点与相似点,以及简单的阐述了多声路超声波流量计的安装过程.     

多声路时差法管道流量计在满拉水电站的应用

流量计是水电站引水系统流量测量的关键设备,满拉水电站使用一种多声路时差法管道流量计,该设备结合当代微电子及数字处理技术,兼具高性能及便于操作的特点,满足水电站对水轮机的效率测量、运行状态监测及水资源管理的要求,实践证明该设备在高原应用是可靠和成功的。     

矿用超声波明渠流量计的设计

针对矿井水中含有的煤粉、泥沙等杂质淤积在明渠流量计探头表面而使其无法正常工作的问题,设计了一种基于M-Bus的矿用超声波明渠流量计。该流量计由量水堰槽、智能超声波流量传感器组成,选定量水堰槽可确定实时流量与实测水头高度的关系式,通过智能超声波流量传感器测出水头高度即可计算出明渠的实时流量。实际应用表明,该流量计具有测量准确、可靠性高、操作简单等优点。     

超声波明渠流量计的设计

介绍了一种超声波明渠流量计。首先,阐述了三角形薄壁堰的流量计算方法,说明了超声波传感器的测量原理及以W77E58作为主控元件的超声波明渠流量计的原理、系统构成和硬件设计,最后,给出了流量计的实测数据,实验表明该流量计具有较高的准确度和可靠性,且价格低廉。     

灌区灌溉用水量管理系统的研究与设计

基于GPRS无线通讯网络技术,提出了一种采用超声波明渠流量计、巴歇尔槽、液位传感器等原件构成的灌区明渠流量测量系统方案。系统可以及时的将传感器采集到的数据,通过GPRS模块无线传输给监控中心的上位机,上位机将接收到的数据进行分析和处理,进而实现上位机对明渠流量计和数据采集仪等仪器的控制。系统以较低的建设成本实现灌区测流管理的自动化和信息化,相对误差较小,能够满足明渠流量计算的精度要求,且实时性好,可靠性高。     

上海肯特推出新产品KEFO型明渠电磁流量计

KEFO型明渠电磁流量计是上海肯特根据水务市场的需求,采用最新技术开发的智能化的流量计,以满足国内日益增长的引水、排水、水处理工程中的流量测量需要。它具有安装方便、维修简便等特点。KEFO型明渠电磁流量计是根据法拉第电磁感应原理制成的,它由明渠电磁流量传感器和电磁流量转化器配套组成。用于连续测量明渠、暗渠或管道中导电液体体积流量。     

基于CAN总线的多路流量测量系统

介绍了Burkert8045电磁流量计输出的数字化处理方法,以及以它为基础设计的一个CAN总线多路流量测量系统.对系统的软硬件工作原理进行了详细的说明.该系统可实现对多路流量测控的无人化、智能化、远程化.     

明渠流量非接触测量

从水力学理论出发,推导出明渠流量非接触测量原理,并介绍一种用于非接触测量明渠流量的超声流量计的实施方案。     

LSQ型超声波明渠微机流量计

ＬＳＱ型超声波明渠微机流量计浙江余姚流量仪表厂新生产的ＬＳＱ型超声波明渠微机流量计采用水力测流、超声波测位、微电脑处理、数字显示和打印记录等技术，能在较恶劣环境下安装、自动计量。具有自动跟踪补偿、自动交直流切换、交流断电续测流量和失电记忆等功能。具有...     

基于P89LPC954单片机的八路四声道超声波流量计测量电路设计

该文介绍了超声波流量计的工作原理,着重描述了该超声波流量计测控系统的结构及其八路四声道测量电路设计。该系统以P89LPC954单片机为核心,其外围电路模块主要包括超声波信号的发射与接收、模拟开关、峰值采样、D／A转换、自动增益控制、显示等。此外,还包括FPGA数据传输及数据分析等功能。应用程序采用模块化编程模式,以方便升级和调试。该流量计主要应用于超声波气体流量测量,实验结果表明,其电路工作稳定,测量精度较高。     

Surface tension driven flow for open microchannels with different turning angles

Present study examines the flow characteristics of open microchannels with sharp turns by experimental and numerical methods. For the open channel system in microscale, the flow is mainly driven by surface tension at atmospheric pressure. The open channels are of various aspect ratios of depth-to-width, ranging from 0.75 to 3, and of turning angles from 45° to 135°. It is found that the turning angle and the aspect ratio of depth-to-width play major roles in the velocity of liquid front advancing, the meniscus of liquid–gas interface shape, and head loss of flow due to turning. Besides, the radius of curvature of the liquid front is reduced as the liquid front travels downstream and over the turning elbow. The loss coefficient remains the same for turning angles less than 75°, whereas it is increased further and is even more pronounced for turning angles larger than 105°. Numerical predications based on conservation laws agree with the experimental observations, and the flow characteristics are well described for open channel in microscale, as the aspect ratio is greater than or near to 1.5.     

Large eddy simulation of turbulent open duct flow using a lattice Boltzmann approach

Large eddy simulations of turbulent open duct flow are performed using the lattice Boltzmann method (LBM) in conjunction with the Smagorinsky sub-grid scale (SGS) model. A smaller value of the Smagorinsky constant than the usually used one in plain channel flow simulations is used. Results for the mean flow and turbulent fluctuations are compared to experimental data obtained in an open duct of similar dimensions. It is found that the LBM simulation results are in good qualitative agreement with the experiments.     

基于GPRS的明渠流速流量检测系统研究

根据明渠流速流量测量技术规范和远距离数据传输的需求,以旋浆式流速仪为一次测量仪器,设计了基于GPRS的明渠流速流量检测系统。系统采用固态存储技术,实现数据在下位机中的大量存储。通过采集电路及GPRS终端,利用通用分组无线业务(GPRS)和Internet网实现远程数据的采集与控制,解决了水文水生态监测中分散数据传输问题,实现了水文信息实时采集传输和处理的无线化、网络化、智能化。     

Multi-block lattice Boltzmann simulations of subcritical flow in open channel junctions

A two-dimensional lattice Boltzmann model (LBM) for subcritical flows in open channel junctions is developed. Shallow water equations coupled with the large eddy simulation model is numerically simulated by the lattice Boltzmann method, so that the turbulence, caused by the combination of the main channel and tributary flows, can be taken into account and modeled efficiently. In order to obtain more detailed and accurate results, a multi-block lattice scheme is designed and applied at the area of combining flows. The model is first verified by experimental data for a 90° junction flow, then is used to investigate the effect of the junction angle on flow characteristics, such as velocity field, water depth and separation zone. The objectives of this study are to validate the two-dimensional LBM in junction flow simulation and compare the results with available experimental data and classical analytical solutions in the separation zone.     

A high-order time integration scheme for open channel flow

The time integration of the linearized, first-order hyperbolic equations for open channel flow usually follows some iterative techniques, the finite difference or the finite element method. Here the matrix exponential approach is used, which can be written in a form to allow for generating an arbitrary high-order approximation to the exact solution.     

Effectiveness of flow obstructions in enhancing electro-osmotic flow

In this paper the influence of obstructions on microchannel electro-osmotic flow is investigated for the first time. To carry out such a study, regular obstructions are introduced into microchannels and flow rates are numerically calculated. The effect of channel width on flow rates is analysed on both free and obstructed channels. The solid material considered for channel walls and obstructions is silicon, and the electrolyte is deionised water. The parameters studied include channel width, obstruction size and effective porosity of the channel. The effective porosity is varied between 0.4 and 0.8 depending on other chosen parameters. The results clearly demonstrate that, under the analysed conditions, introduction of obstructions into channels wider than \(100\,\upmu \hbox {m}\) enhances the flow rate induced by electro-osmosis.     

Identification of equivalent topography in an open channel flow using Lagrangian data assimilation

We present a Lagrangian data assimilation experiment in an open channel flow above a broad-crested weir. The observations consist of trajectories of particles transported by the flow and extracted from a video film, in addition to classical water level measurements. However, the presence of vertical recirculations on both sides of the weir actually conducts to the identification of an equivalent topography corresponding to the lower limit of a surface jet. In addition, results on the identification of the Manning coefficient may allow to detect the presence of bottom recirculations.     

An investigation of turbulent open channel flow with heat transfer by large eddy simulation

Large eddy simulation of fully developed turbulent open channel flow with heat transfer is performed. The three-dimensional filtered Navier-Stokes and energy equations are numerically solved using a fractional-step method. Dynamic subgrid-scale (SGS) models for the turbulent SGS stress and heat flux are employed to close the governing equations. Two typical temperature boundary conditions, i.e., constant temperature and constant heat flux being maintained at the free surface, respectively, are used. The objective of this study is to explore the behavior of heat transfer in the turbulent open channel flow for different temperature boundary conditions and to examine the reliability of the LES technique for predicting turbulent heat transfer at the free surface, in particular, for high Prandtl number. Calculated parameters are chosen as the Prandtl number (Pr) from 1 up to 100, the Reynolds number (Re_τ) 180 based on the wall friction velocity and the channel depth. Some typical quantities, including the mean velocity, temperature and their fluctuations, heat transfer coefficients, turbulent heat fluxes, and flow structures based on the velocity, vorticity and temperature fluctuations, are analyzed.     

An investigation of pulsating turbulent open channel flow by large eddy simulation

Pulsating turbulent open channel flow is investigated by use of large eddy simulation (LES) technique coupled with a dynamic subgrid-scale (SGS) model for turbulent SGS stress. The three-dimensional filtered Navier-Stokes equation is numerically solved by a fractional-step method. The objective of this study is to deal with the behaviors of pulsating turbulent open channel flow, in particular turbulence characteristics in the free surface-influenced layer, and to examine the reliability of the LES approach for predicting the pulsating turbulent flow with a free surface. In this study, the frequency of driving pressure gradient ranges low, medium and high value. The mean and phase-averaged statistical turbulence quantities, the resolved turbulent kinetic energy and Reynolds stresses budgets, and the flow structures are obtained and analyzed. With the increase of the driving frequency, the depth of the surface-influenced layer increases and the turbulent Stokes length near the bottom wall decreases. Different turbulence characteristics between the accelerating and decelerating phases are interpreted comprehensively. Turbulence intensities reveal that turbulent flow has a strong anisotropy in the free surface-influenced layer, in particular in the decelerating phases during the pulsating cycle. The budget terms of the resolved turbulent kinetic energy, the vertical and spanwise Reynolds stresses in the free surface region are analyzed. The flow structures clearly exhibit that bursting processes near the bottom wall are ejected toward the surface and the most surface renewal events are closely correlated with the bursting processes. These processes are strengthened during the decelerating period since strong turbulence intensities are generated.     

Artificial neural network modelling in simulation of complex flow at open channel junctions based on large data sets

The flow characteristics in open channel junctions are of great interest in hydraulic and environmental engineering areas. This study investigates the capacity of artificial neural network (ANN) models for representing and modelling the velocity distributions of combined open channel flows. ANN models are constructed and tested using data derived from computational-fluid-dynamics models. The orthogonal sampling method is used to select representative data. The ANN models trained and validated by representative data generally outperform those by using random data. Sobols' sensitivity analysis is performed to investigate contributions of different uncertainty sources to model performance. Results indicate that the major uncertainty source is from ANN model parameter initialization. Hence an ANN model training strategy is designed in order to reduce the main uncertainty source: models are trained for many runs with random model parameter initializations and the model with the best performance is adopted.