Effective parameters for calculating discharge coefficient of sluice gates

The present work demonstrates the characteristics of flow from sluice gates under free and submerged flow conditions using Energy and Momentum Equations (EMEs). The experimental data was used from the research works reported by different investigators to calibrate the proposed equations. An equation for estimation energy loss factor of sluice gate at free flow was presented and effect of this parameter on increasing discharge coefficient's accuracy was demonstrated. It was derived a theoretical equation for variations of sluice gate's discharge coefficient with relative opening and relative tailwater depth. Effects of energy loss factor on discharge coefficient and distinguishing limit were investigated. In this research the concepts of submergence limit of the gate and the submergence limit of hydraulic jump will be distinguished. By determining effective pressure on the gate and using EMEs, equations for variations of sluice gate's contraction coefficient with relative opening and relative submergence were presented. The result shows that at free flow condition, a minimum contraction coefficient obtained under a certain value of relative gate opening. At submerged flow condition, contraction coefficient would be either increased or decreased depending on the level of flow submergence. This paper carefully considered stage-discharge relationships for estimation gate discharge under free and submerged flow conditions.     

General purpose flow measurement equations for flumes and thin plate weirs

As a result of a need identified by operators of wastewater and waterworks plants for simplified discharge equations to monitor flow through their works, the paper presents general purpose equations for this purpose. They are based on calibrations carried out on rectangular standing wave flumes and thin plate weirs, and the established discharge equations given in international and British standards. The general purpose equations enable the operators to carry out spot checks of flow quickly, which is an important consideration in managing these works. For more precise work in flow measurement, however, the paper recommends that international and British standards should be used; for convenience, these equations are also included in the paper.     

Radial Basis Neural Network and Particle Swarm Optimization-based equations for predicting the discharge capacity of triangular labyrinth weirs

Conventional weirs are utilized for controlling, measuring and adjusting the flow depth in hydraulic structures, such as those found in irrigation and drainage networks. Various weirs with modified shapes are utilized to increase the discharge capacity. The main goal of this study is to investigate the discharge coefficient (C_d) of triangular labyrinth weirs using soft computing methods. The performance of the Radial Basis Neural Network (RBNN) is compared with that of Multiple Nonlinear and Multiple Linear Particle Swarm Optimization (MNLPSO and MLPSO). Models developments are conducted using published experimental data from the literature. Comparing the RBNN, MLPSO and MNLPSO results obtained through these soft computing techniques with experimental data shows that all models perform well in predicting the discharge coefficient of a triangular labyrinth weir. Performance of the proposed approaches which demonstrated explicit equation given by MNLPSO model provided the discharge capacity with lower error (RMSE=0.0223) is compared with the MLPSO (RMSE=0.0346) and RBNN (RMSE=0.045) approaches.     

Superconducting switch for large heat flow below 50 mK

We describe both the method of fabrication and the performance of a zinc superconducting heat switch used to couple thermally the mixing chamber of a dilution refrigerator and a nuclear demagnetization refrigerator.     

Performance evaluation of two different neural network and particle swarm optimization methods for prediction of discharge capacity of modified triangular side weirs

Technical design of side weirs needs high accuracy in predicting discharge coefficient. In this study, discharge coefficient prediction performance of multi-layer perceptron neural network (MLPNN) and radial basis neural network (RBNN) were compared with linear and nonlinear particle swarm optimization (PSO) based equations. Performance evaluation of the model was done by using root mean squared error (RMSE), coefficient of determination (R²), mean absolute error (MAE), average absolute deviation (δ) and mean absolute relative error (MARE). Comparison of the results showed that both neural networks and PSO based equations could determine discharge coefficient of modified triangular side weirs with high accuracy. The RBNN with RMSE of 0.037 in test data was found to be better than MLPNN with RMSE of 0.044 and multiple linear and nonlinear PSO based equations (ML-PSO and MNL-PSO) with RMSE of 0.043 and 0.041, respectively. However, due to their simplicity, PSO based equations can be sufficient for use in practical cases.     

The compressible flow discharge coefficients for a two-dimensional slit

Exact and approximate methods for evaluating the compressible flow coefficients of discharge for a two-dimensional slit are compared. Experiments over a wide range of pressure show that the discharge coefficients agree closely with the values obtained from the solutions of the irrotational equations (i.e. with no mixing region). The approximate methods of calculating the discharge coefficients given by Jobson and Bragg are shown to give good agreement with the exact solution, although there is some small divergence in the high pressure ratio region.     

On a flow meter for discharge measurement in irrigation channels

Flow characteristics of a simplified constricted width flow meter are investigated in this paper. It is a very simple device, which is not only easy to construct and operate but also maintenance free. The rate of flow can be estimated for both free and submerged flow conditions. The device can find applications in measurement of discharge in irrigation channels provided in small catchments.     

Capacitive and barrier discharge excilamps and their applications (Review)

The results of studies, development works, and tests of barrier-and capacitive-discharge excilamps radiating in the UV and VUV spectrum regions are presented. The main information on the designs of radiators and generators is presented. The spectral, temporal, and energy characteristics of excilamps based on the emission of KrCl*, XeCl*, XeI*, XeBr*, KrBr*, Xe*₂, Br*₂, and Cl*₂ molecules and the I* atomic line are described. It is shown that the created generators and sealed-off radiators have long service lives. Examples of specific applications of excilamps are presented.     

Effect of the powder concentration and dielectric flow in the surface morphology in electrical discharge machining with powder-mixed dielectric (PMD-EDM)

The addition of powder particles to the electrical discharge machining (EDM) dielectric fluid modifies some process variables and creates the conditions to achieve a higher surface quality in large machined areas. This paper presents a new research work that aims to study the improvement in the polishing performance of conventional EDM when used with a powder-mixed-dielectric (PMD-EDM). The analysis was carried out varying the silicon powder concentration and the flushing flow rate over a set of different processing areas and the effects in the final surface were evaluated. The evaluation was done by surface morphologic analysis and measured through some quality surface indicators. The results show the positive influence of the silicon powder in the reduction of crater dimensions, white-layer thickness and surface roughness. Moreover, it was demonstrated that an accurate control of the powder concentration and flushing flow is a requirement for achieving an improvement in the process polishing capability.     

Real-time method for NO(2) flow measurements

Measurements of NO(2) flows are made without requiring prior experimental calibration of the flow meter. A tapered, variable area flow meter with a diameter ratio scale is used to make the real-time NO(2) flow measurements. The necessary parameters and calculations used to determine the viscosity and density of the flowing N(2)O(4)2NO(2) gas are presented. The limits of error associated with these parameters and errors associated with controlled flow measurement conditions are considered. Disregarding the scale reading error, which depends on the flow meter utilized, the limits of error are found to yield a measurement error less than 7%.     

一种改进的联合相容SLAM数据关联方法

数据关联是SLAM的难点之一。联合相容分枝定界算法(JCBB)虽能得到可靠的关联结果,但计算量随观测数目的增加而迅速提高,实时应用受到限制。通过给定联合相容配对个数的上限,对JCBB算法进行了改进,提出了一种快速JCBB算法(FJCBB)。FJCBB与JCBB有相同的关联效果,但计算量随观测数目的增加变化缓慢。当观测数目较大时,FJCBB的计算时间大幅减小,优势十分明显。最后,通过大量实验,验证了该方法的有效性。     

Analysis of hydraulic characteristics for hollow semi-circular weirs using artificial neural networks

Weirs are small overflow dams used to alter and raise water flow upstream and regulate or spill water downstream watercourses and rivers. This paper presents the application of artificial neural network (ANN) to determine the discharge coefficient (Cd) for a hollow semi-circular crested weirs. Eighty five experiments were performed in a horizontal rectangular channel of 10 m length, 0.3 m width and 0.45 m depth for a wide range of discharge. The results of examination for discharge coefficient were yielded by using multiple regression equation based on dimensional analysis. Then, the results obtained were also compared using ANN techniques. A multilayer perceptron MLP algorithm FFBP network was developed. The optimal configuration of ANN was [2,10,1] which gave mean square error (MSE) and correlation coefficient (R) of 0.0011 and 0.91, respectively. Performances of ANN model reveal that the Cd could be better estimated by the ANN technique in comparison with Cd obtained using statistical approach.     

基于热交换的放出法测试流量特性的研究

给出了固定容积放气过程的热力学模型,提出了仅根据"停止法"的瞬态压力曲线求出容器壁和内部空气换热系数的方法,并应用于定容积放出法测量电磁阀的流量特性的数据处理过程中.从测试结果可以看出,在定容积放出法中考虑热交换可以很大程度提高测试结果的精度.并分析了换热系数对测试结果的影响.     

Application of Immersed Boundary Method for flow over stationary and oscillating cylinders

IBM (Immersed Boundary Method) with feedback momentum forcing was applied to stationary and moving bodies. The capability of IBM to treat the obstacle surfaces, especially with moving effect has been tested for two dimensional problems. Stationary and oscillating cylinders were simulated by using IBM based on finite volume method with Cartesian coordinates. For oscillating cylinder, lateral and vertical motions are considered, respectively. Present results such as time histories of drag and lift coefficients for both stationary and oscillating cases are in good agreement with previous numerical and experimental results. Also, the instantaneous wake patterns of oscillating cylinder with different oscillating frequency ratios well represented those of previous researches. More feasibility study for IBM has been carried out to two oscillating cylinders. Drag and lift coefficients are presented for two cylinders oscillating sinusoidally with phase difference of 180°.     

Probe and method for simultaneous measurements of 'true' instantaneous temperature and three velocity components in turbulent flow

In the measurement of turbulent flows the need has always existed to obtain correct instantaneous values of temperature and three components of velocity at a particular point. Many proposed lengthy approximate correction methods that attempt to account for 'nonlinear' effects (cross contamination between different quantities) in hot-wire measurements cannot be considered satisfactory. The availability of powerful digital computers for theoretical and experimental studies has placed pressure on experimentalists to develop better probes and methods. This paper attempts to answer these pressures by describing the development of a special four-wire probe and a method of processing the obtained signals. The use of four 0.625-microm-diam sensors makes the probe practically interference free. The processing method is based on the simultaneous solution of four complete nonlinear response equations for the sensors, yielding in principle exact instantaneous values of velocity components and temperature. Additional features of the processing method include: instantaneous full correction for tunnel free stream velocity and temperature fluctuations, first-order correction for dc drifts of the signals during data acquisition, subtraction of all 60-Hz related noise, and correction for streamwise displacement of sensors based on instantaneous streamwise velocity.     

Computation of water and air flow with submerged hydrofoil by interface capturing method

Free-surface flows with an arbitrary deformation, induced by a submerged hydrofoil, are simulated numerically, considering two-fluid flows of both water and air. The computation is performed by a finite volume method using unstructured meshes and an interface capturing scheme to determine the shape of the free surface. The method uses control volumes with an arbitrary number of faces and allows cellwise local mesh refinement. The integration in space is of second order, based on midpoint rule integration and linear interpolation. The method is fully implicit and uses quadratic interpolation in time through three time levels. The linear equations are solved by conjugate gradient type solvers, and the non-linearity of equations is accounted for through Picard iterations. The solution method is of pressure-correction type and solves sequentially the linearized momentum equations, the continuity equation, the conservation equation of one species, and the equations for two turbulence quantities. Finally, a comparison is quantitatively made at the same speed between the computation and experiment in which the grid sensitivity is numerically checked.     

A method for extracting surface flow velocities and discharge volumes from video images in laboratory

The lack of hydrological data has been identified as one of the major obstacles facing the effective evaluation of hydraulic and hydrological interventions in the field. Traditional methods of data collection have proven to be generally expensive and particularly risky under high flow conditions. A method for quantifying hydrodynamic variables, such as surface flow velocity and discharge volume was developed in a laboratory setting using video images. This method explores several innovative image analysis techniques, specifically the Image Variance (IV) and Threshold Segmentation with Path Discretization (TSPD), where the basics steps comprise image capture, rectification and data extraction. Measurements obtained from conventional instruments and data extracted from video images were compared and exhibited less than 2.5% difference. It can be concluded that under laboratory conditions it is possible to obtain reliable velocities and discharges from video techniques, without being in contact with the flow.     

A neural network approach for prediction of discharge in straight compound open channel flow

Most natural rivers and streams consist of two stage channels known as main channel and flood plains. Accurate prediction of discharge in compound open channels is extremely important from river engineering point of view. It helps the practitioners to provide essential information regarding flood mitigation, construction of hydraulic structures and prediction of sediment load so as to plan for effective preventive measures. Discharge determination models such as the single channel method (SCM), the divided channel method (DCM), the coherence method (COHM) and the exchange discharge method (EDM) are widely used; however, they are insufficient to predict discharge accurately. Therefore, an attempt has been made in this work to predict the total discharge in compound channels with an artificial neural network (ANN) and compare with the above models. The mean absolute percentage error with artificial neural networks is found to be consistently low as compared to other models.     

Multi-spark simulation of the electrochemical discharge machining (ECDM) process

Journal of Mechanical Science and Technology - Electrochemical discharge machining (ECDM) has been studied numerically by several researchers using single spark simulation during finite element...     

膜片稳压溢流阀的设计计算

在对低压大流量的溢流阀建立平衡方程及确定设计基本原则的基础上，进行了阀的设计计算及性能分析。