Coefficient Of Discharge For A Combined Hydraulic Measuring Device (original) (raw)

Study Coefficient of Discharge for a Combined Free Flow over Weir and under Gate for Multi Cases

Weirs and gates are the common and important structures which are used in controlling and adjusting the flow in irrigation channel. One disadvantage of the gates is the possibilities of retaining the floating materials which can be resolved if they combined with the weirs. Also sedimentation problem in weir can be resolved by combination of weirs with sluice gates. These combined structures have a new hydraulic condition that is different with weir condition solely or we have only gate. This study was done in the fluid lab of civil engineering in Babylon University .This research presents the results of an experimental study on the hydraulic characteristics of weirs and combined weirs under multi cases, these cases were (rectangle weir, v-notch weir, semicircular weir, rectangular combined weir with a rectangular gate, v-notch combined weir with a rectangular gate, semi-circular combined weir with a rectangular gate, and semicircular combined weir with a semi-circular gate). The results showed that the experiments erected on the notches were obtained for discharge coefficient Cd as follows: Rectangular weir Cd = 0.607 , V_ notch Cd = 0.630 , Semicircular weir Cd = 0.693 , Combined V-notch weir and Rectangular gate Cd = 0.779 , Combined Rectangular weir and Rectangular gate Cd = 0.751 , Combined semicircular weir and Rectangular gate Cd = 0.781 and Combined semicircular weir and semicircular gate Cd = 0.797. We found the values Cd in the Compound semicircular weir and semicircular gate are the best in terms of being a once hydraulic values Cd higher than the other notches.

Coefficient Of Discharge For A Compound Weir Combined With Semi Circular Gate

2013

The commonly used cross sections of weirs are sharp crested rectangular, trapezoidal and triangular, however; the measurement accuracy of single sharp crested weir is abated in areas where flows exhibits great variability, i.e. the flow ranging from very low flow in dry conditions to very high flow in extreme rainfall events. In top of that, generally the weirs have the problem of accumulation the sedimentation in the weir pond, so to minimize the disadvantage of weirs, it can be merged with gates (which also have the problem of retaining the floating materials) in one device. The main objective of this study is to investigate the coefficient of discharge and the characteristics of the free flow for a compound weir (have rectangular notch over triangular notch with trapezoidal notch between them) and semi circular sluice gate of fixed dimensions. Fifteen combined device models were constructed and tested under various geometrical conditions and constant hydraulic conditions. The res...

Development of Parabolic Weirs for Simplified Discharge Measurement

Biosystems Engineering, 2007

Discharge equations of all existing sharp crested flow measurement weirs involve some fractions such as exponents of flow depth, which make manual calculations difficult. In the present research work, weirs with a simplified discharge equation were designed by manipulating the weir profile so that the flow depth exponent was a whole number. A parabolic weir profile gave the simplified discharge equation with two as the flow depth exponent. A relationship for obtaining the parabolic weir profile with any weir angle was developed. The theoretical discharge of flow across the parabolic weir was derived using a geometric constant based on the weir profile. Four parabolic weirs with 301, 451, 601, and 901 weir angles were developed and evaluated in laboratory hydraulic flume. The flow regime across weirs was turbulent and the average coefficient of discharge was estimated as 0Á5570Á05. Weir angle specific discharge models (coefficient of determination R 2 X0Á986) were developed based on two approaches; the first based on the product of geometric constant and the mean coefficient of discharge, and the second on a non-linear regression model constant. Weir constant linear regression prediction equations (R 2 X0Á993), capable of predicting discharge characteristics in combination with discharge models at any intermediate weir angle, were fitted. Parabolic weirs have the merits of both rectangular and triangular weirs, and may find application in field irrigation, industrial flow, and automated control systems measurements.

Computation of discharge for simultaneous flow over weirs and below gates (H-weirs)

Flow Measurement and Instrumentation, 2013

Simultaneous flow over weirs and below gates for free flow condition is experimentally investigated. Combination of a sharp-crested rectangular weir and rectangular gate is considered as a flow measurement structure which is named as H-weirs. H-weirs are defined by the width of the weir and gate openings, the height of the gate opening and the vertical distance between bottom of the weir and top of the gate. Laboratory experiments are conducted by measuring the discharge and the depth of water at upstream for different H-weirs. The present study aims to determine the discharge for a given H-weir simply by reading the depth of water at upstream of the combined structure. The compatibility of various formulations of the discharge-depth of water relationship is investigated by using the collected data and two new formulations are suggested based on the analysis of these data. After obtaining and comparing percentage errors of each equation, it is concluded that the new proposed equations can be used to accurately predict the discharge through H-weirs within the given ranges of the experimental study.

Calibration of Compound Broad Crested Weir For Measurement of Discharge Ms

2017

Experiments were carried out to know the suitability of different shapes of broad crested weirs to replace the conventional method of discharge measurement with the help of venturi-flume. Even the weir used for it, had an indepen0dent use as energy dissipater. A series of laboratory experiments were performed in order to investigate the effects of the lower weir crest and step height of a broad-crested weir of rectangular compound cross section on the values of discharge coefficient, the approach velocity and the modular limit. The dependence of the three values on model parameters was investigated and the quantities were compared with those of the broad crested weir models with rectangular cross section. KeywordsCo-efficient of Discharge, Calibration of Weir,Broad crested weir, Discharge measurement, DepthDischarge relationship.

Broad-Crested Weir as a Device for Measurement of Discharge

Weirs are overflow structures, which alter the discharge so that flow rate can be calculated, flood can be prevented, or even make a body of water more navigable. Measurements of discharge are known based on the surface profile of the water. For estimation of discharge over the weir, weir coefficient is required. In this report only the broad crested weir is focused on. Design and the analysis of this weir are shown in the report. It was found that the broad-crested weir is best for measuring discharge in small medium channels. Flow over a broad-crested weir is highly dependent on the weir's geometry, it's a useful hydraulic tool which enables engineers to control water height, velocity, and most importantly they can be used to calculate discharge. Hydraulic structures such as weirs, flumes, and pipes, may cause the flow upstream of the structure to rise above the normal flow depth this is a common property.

Experimental Study of Combined Oblique Weir and Gate Structure

2013

Flow measurement in open channel is important to support the system management. An experimental study in a laboratory flume is carried out to study flow over a sharp crested weir and under gate in combined structure as flow measurement device. Four different oblique angles to the longitudinal axis of the channel and four different heights of gate opening were used. The basic principles of statistical analysis are employed to correlate between the hydraulic and geometric dimensionless parameters with the discharge coefficient. Different relationship models with acceptable significance are suggested. It was found that the maj or parameters effecting significantl y on discharge coefficient are (h/d, α, L/d, P/d), and value of Cd range from 0.623 to 0.403, with Standard Error 0.0047. Within the limitations of the present experimental work two different discharge equations were predicted. The first equation Which assumed that the coefficient of discharge is the same for weir and gate wit...

Discharge Measurements in Open Channels using Compound Sharp-Crested Weirs

Engineer: Journal of the Institution of Engineers, Sri Lanka

Compound sharp-crested weirs have been widely used for measuring discharges in open channels accurately with a reasonable sensitivity over a wide flow range. The flow characteristic over a compound sharp-crested weir is completely different that of a single sharp-crested weir. The most common type of compound sharp-crested weir used in irrigation canals is the combination of a rectangular notch and a 'V' notch with a small notch angle. However, the continuity of flow and precision of this type of compound weirs are reported to be poor in the transition region between two sections. As an improvement, a compound sharp-crested weir composed of two triangular parts with different notch angles has been designed and experimentally validated which proved to be accurate in measuring wide range of discharges without any discontinuity. Several methods are also proposed to estimate the flow over the double 'V' notch compound sharp-crested weir and one method is experimentally validated as most suitable.

Development of rectangular broad-crested weirs for flow characteristics and discharge measurement

KSCE Journal of Civil Engineering, 2014

One of the important problems which designers and engineers are faced with is proper measurement of water flow rates in open channels and rivers. To solve this problem, the water discharge to be precisely measured in water conveyance systems such as off takes and distribution ditches. The common procedure to meet this requirement is achieved by using water-measuring structures such as flumes, orifices, weirs and current meters. Among the mentioned structure, engineers prefers the weirs because of their simple structure and economical features. The broad-crested rectangular weirs are very common which are widely used in water ways and canals. In this study, the effect of steeping in the upstream side of rectangular broad-crested weirs over discharge coefficient and flow characteristics is investigated. Five weirs with 15, 30, 45, 60 and 90 weir angles were developed and flow discharge coefficient, negative velocity over the weir crest edge and water surface profiles along the weir crest evaluated in laboratory hydraulic flume. The obtained results showed by decreasing the slope of the upstream side, discharge efficiency and the discharge capacity of the weir are increased subsequently. Consideration of experimental data it is obvious that by using the proposed weir with slope of 15 degree in comparison with standard weir, the efficiency is increased up to 19.17%. It is noteworthy that by reducing the slope, return current on the crest is not observed.

Combined-free flow over weirs and below gates

Discharge-measuring structures such as weirs have been studied by many researchers. Discharge equations derived from energy considerations are calibrated by experimental data for typical weir geometries. In all measuring structures definition of a discharge coefficient is unavoidable to represent influences of parameters that are not directly included in the derivation of the discharge equation. Restrictions and limitations on the use of discharge equations are also reported in the literature . Discharge coefficient is usually dependent on dimensionless parameters such as Reynolds and Weber numbers associated with dynamic conditions of flow over the structure, and ratios of weir dimensions which reflects variations in the geometrical design of the measuring structures.