M. Heidarpour, H. Afzalimehr, E. Khorami,
Volume 6, Issue 3 (10-2002)
Abstract
Of the many hydraulic structures developed by man, the weir is perhaps the oldest. Weirs are used for the measurement of discharge and regulation of water flow. The most common types of weirs are broad-crested, sharp-crested, circular-crested and cylindrical, and ogee crest weirs. Advantage of the circular-crested and cylindrical weir compared to the other weirs include simplicity of design, stable overflow pattern, larger coefficient of discharge and the associated lower costs. In the present study, potential flow around a circular cylinder are adapted to determine the velocity distribution at the crest section and to develop a model for coefficient of discharge (Cd) for circular-crested weirs. These results were evaluated using present test data for three types of weir models, namely, cylindrical, semicylindrical and semicylindrical with different heights and also Dressler theory. The results of the study showed that the experimental velocity profile agree very well with the theoretical profiles for the range of the study. Also, the prediction of the velocity distribution over the weir crest using Dressler theory is always less than the proposed model and measured data. The predicted values of coefficient of discharge (Cd) based on the proposed model agree well with Cd determined from direct discharge measurements. For the cylindrical model, the coefficient of discharge can be predicted from the proposed model within an error of –7% and for the semicylindrical and semicylindrical with different heights within ± 5%.
A. Alizadeh, B. Yaghoubi, S. Shabanlou,
Volume 24, Issue 2 (7-2020)
Abstract
In this study, the discharge coefficient of sharp-crested weirs located on circular channels was modeled using the ANFIS and ANFIS-Firefly (ANFIS-FA) algorithm. Also, the Monte Carlo simulations (MCs) were used to enhance the compatibilities of the soft computing models. However, the k-fold cross validation method (k=5) was used to validate the numerical models. According to the input parameters, four models of ANFIS and ANFIS-FA were introduced. Analyzing the numerical results showed that the superior model simulated the discharge coefficient as a function of the Froude number (Fr) and the ratio of flow depth over weir crest to the weir crest height) h/P(. The values of the mean absolute relative error (MARE), root mean square error (RMSE) and correlation coefficient (R) for the superior model were calculated 0.001, 0.002 and 0.999, respectively. However, the maximum error value for this study was less than 2%.
M. Sabouri, A.r. Emadi, R. Fazloula,
Volume 26, Issue 2 (9-2022)
Abstract
A compound sharp-crested weir is often used to measure a wide range of flows with appropriate accuracy in open channels. In this study, experiments were performed to investigate the hydraulic flow through a compound weir of circular-rectangular with changes in hydraulic and geometric parameters in free and submerged flow conditions. The characteristics of the weirs include rectangular spans width of 39 cm, a circular radius of 5, 7.5, and 12.5 cm, and heights of 10 and 15 cm. The results showed that by increasing the radius and height of the Weir, upstream water depth increases around 28.4%. At a constant h/p, the discharge coefficient increases with the increasing radius of the circular arc. Also, in the submerged conditions, the discharge coefficient is less (around 40%) than in the free flow condition, which is due to the resistance of the depth of the created stream against the passage of the flow.
