Pengujian Pengaruh Ketinggian Weir pada Koefisien Discharge dari Weirmeter Sharp-Crested V-Notch 90o (original) (raw)
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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.
How to citeDetermination of discharge coefficient in the tilted crown sharp-crested weirs
Journal of Applied Research in Water and Wastewater, 2022
In this study, the performance of vertical and tilted crown weirs with different angles of the weir crest across the flow has been investigated using numerical and experimental models. Accordingly, various experiments are conducted on tilted crown sharp-crested weirs under different free-flow conditions. Moreover, computational fluid dynamic (CFD) modeling has been done using Fluent software to determine the best form of the discharge coefficient (Cd). In this study, the RNG model is used to define turbulence in the fluid flow and the two-phase volume of fluid (VOF) method is applied to define the interface of water-air in the flume. To verify the accuracy of the CFD model, the experimental data that was done in this research are used. Moreover, another goal of this research is to investigate the influence of the different angles of weir on hydraulic characteristics of flow such as pressure, velocity and Cd parameters. The results show that by increasing the weir crest angle across the flow (α), the Cd values are almost constant. Furthermore, the numerical results are in good agreement with the experimental models. As, the comparison of numerical and experimental data shows that the maximum absolute relative error (ARE) obtained are 2.8 %, which indicates the high accuracy of the CFD model. The vortex area with return velocity vectors can be seen in downstream of the weir and these vectors increase near the weir. In all velocity values, by decreasing the angle of weir to the flow direction, the Cd values increased and tends to a constant value while, the pressure values decreased. As for the velocity values in ranges of 0.05-0.23 m/s, the Cd value is ranged in 0.64-0.675. Finally, as the Reynolds and Froude number increase, the discharge coefficient decreases and tends to a constant number of 0.65 approximately.
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.
Discharge Formula for Sharp-Crested Rectangular Weirs
Sharp-crested rectangular weirs are commonly used as discharge measuring facilities in open channels and laboratories. Weir plate height and width are two key elements in shaping the head-discharge relationship. The experiments demonstrate that for a certain range of discharge over the weir, height of the plate is no longer affecting the discharge. Average velocity over the weir plotted against the weir head has a unique behavior. This behavior can be used in such a way that can define a weir velocity to estimate the discharge rather than using the discharge coefficient. Hence a more accurate outcome and a more compact and short form of expressions are expected to be obtained. The present study focuses on the experimental investigation of various possible formulations of the weir velocity for available weir heights and widths.
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.
Discharge Coefficient of Half Circle Notch Sharp-Crested Weirs : preliminary Experimental Approach
A preliminary experimental work were conducted to evaluate the hydraulics performance of half circle notch sharp-crested weir. The evaluation of results shows that , the variation of flow width crossing the circular notch not only affects the value of discharge coefficient but also have an influence on the exponent of the flow rate formula , the regression of the experimental results refers that the exponent of head would approaching to,2, compared to,1.5, and 2.5 those featured the fully contracted rectangular and V-notch weirs predictive formulas respectively. According to this finding the new formulas related the weir coefficient, C w and the discharge coefficient ,C d , were correlated corresponding with regressed curves to be helpful for designers related to this kind of weir. The study , also shows that , in spite of the simplicity of a present equation , its usefulness were at an acceptable error compared with previously presented by another researchers that have more complicated in configuration and related factors , wherefore , it may be impractical. Thereby the simplicity and an acceptable precise of a present formula refers to be a useful tool for practical purposes .
Triangular weirs are commonly used to measure discharge in open channel flow, representing an inexpensive, reliable methodology to monitor water allocation. In this work, a low-speed photographic technique was used to characterize the upper and lower nappe profiles of flow over fully aerated triangular weirs. A total of 112 experiments were performed covering a range of weir vertex angles (from 30°to 90°), crest elevations (8 or 10 cm), and discharges (0.01-7.82 l s −1 ). The experimental nappe profiles were mathematically modeled and combined with elements of free-vortex theory to derive a predictive equation for the weir discharge coefficient. Comparisons were established between measured C d , the proposed discharge coefficient equation, and discharge coefficient equations identified in the literature. The proposed equation predicts C d with a mean estimation error (MEE) of 0.001, a root-mean square error (RMSE) of 0.004, and an index of agreement (IA) of 0.984. In the experimental conditions of this study, this performance slightly improves that of the equation proposed by Greve in 1932, and showed the same absolute value of MEE but lower values of RMSE and IA.
Discharge formula based on brink depth over sharp-crested weirs
water supply, 2024
Weirs are among the most essential hydraulic structures for measuring water discharge in open channels. The prediction of water discharge over weirs should be as precise and straightforward measured as feasible. The experimental investigation of flow prediction over varied heights of a conventional rectangular sharp-crested weir was conducted in the present work. The investigation evaluated five ratios of weir height to length, P/b, of 0.33, 0.4, 0.47, 0.53, and 0.6, different water discharges, Q, of up to 17.25 L/s, and different bed slopes, S, between 0.001 and 0.01. The experiment’s findings reveal that a change in the bed slope has no significant effect on the brink depth, hb, for a constant water discharge. However, it influences the head over the weir, h, which is usually measured upstream of the weir location and used to predict water discharge. A simple, accurate formula was developed for predicting water discharge over rectangular sharpcrested weirs depending on the brink depth with mean absolute percent error (MAPE) and root-mean-square error (RMSE) of 1.714% and 0.229, respectively. In addition to having a simple form, the developed formula performs well, is unaffected by the bed slope, and applies to a wide range of h/P values, from 0.158 to 0.945.
Discharge Coefficient of Contracted Rectangular Sharp-Crested Weirs, an Experimental Study
Journal of Engineering
An experimental study is made here to investigate the discharge coefficient for contracted rectangular Sharp crested weirs. Three Models are used, each with different weir width to flume width ratios (0.333, 0.5, and 0.666). The experimental work is conducted in a standard flume with high-precision head and flow measuring devices. Results are used to find a dimensionless equation for the discharge coefficient variation with geometrical, flow, and fluid properties. These are the ratio of the total head to the weir height, the ratio of the contracted weir width to the flume width, the ratio of the total head to the contracted width, and Reynolds and Weber numbers. Results show that the relationship between the discharge coefficient and these variables is a non-linear power function with a determination coefficient of 0.97. The importance and normalized importance analysis show that 56.3 % of the discharge coefficient variation is explained by the head-to-contracted width of the weir r...