Weir velocity formulation for sharp-crested rectangular weirs

Discharge in open channels can be measured by sharp-crested rectangular weirs. Generally, measured head over the weir crest is substituted into an empirical formula derived from energy considerations to calculate the discharge. Assumptions made on the derivation are taken into account by defining a discharge coefficient that fits into the experimental data. In this study, a physical quantity, the average velocity over the weir section defined as 'weir velocity' is directly formulated as function of weir geometry and head over the weir. Weir velocity plotted against the weir head has a universal behavior for constant weir width to channel width ratio independent of the weir size. This unique behavior is described in terms of weir parameters to calculate the discharge without involving a discharge coefficient. Combining weir velocity data for variable weir widths provides a basis for direct formulation of discharge. The weir velocity exhibits simpler functional dependency on weir parameters in contrast to the discharge coefficient.


Discharge formula for rectangular sharp-crested weirs
Aydın, İsmail; Altan Sakarya, Ayşe Burcu (2011-04-01)
Sharp-crested rectangular weirs used for discharge measurement in channels and laboratories are experimentally investigated. Height and width of weir plate are the two parameters characterizing the head-discharge relationship. Laboratory experiments are conducted by measuring the discharge and the head over the weir for variable weir heights and widths. Applicability of various formulations for the discharge coefficient are investigated. Experiments indicate that discharge is independent of weir height, whe...
Stream gauging by combined use of surface PTV and CFD techniques in channel flows
GHARAHJEH, Sİamak; Aydın, İsmail (2015-07-03)
A video imagery technique for free surface velocity measuring is presented and used to calculate discharge for uniform open channel flows numerically. When the surface velocities are measured and used as boundary conditions on the water surface, velocity field can then be solved numerically to satisfy the surface boundary conditions. This approach can provide a precise tool for velocity field, discharge and boundary shear distribution calculation. PTV or particle tracking velocimetry is implemented over the...
Wall functions for boundary roughness prediction in uniform channel flows
Aydın, İsmail (null; 2017-08-18)
Boundary roughness is an important hydraulic parameter in describing dynamics of free surface flows. There is no direct method to estimate the possible boundary resistance in natural environment. Available empirical formulations are based on the particle
Flow measurement in open channels by combined use of free surface PİV and CFD
Gharahjeh, Siamak; Aydın, İsmail; Department of Civil Engineering (2016)
Stream discharge measurement in open channels is of great importance in hydraulic engineering. For many years, classical devices such as propellers, current meters and weirs have been used for this purpose. In recent times, non-intrusive methods such as PIV (Particle Image Velocimetry) and PTV (Particle Tracking Velocimetry) have been very popular as they are more practical and convenient to automatically collect water free surface velocity which is further analyzed for discharge measurement. Image processi...
Numerical modelling of contracted sharp crested weirs /
Duru, Aysel; Altan Sakarya, Ayşe Burcu; Kökpınar, M. Ali; Department of Civil Engineering (2014)
Sharp crested weirs and gates are flow measurement structures which are frequently used for discharge measurements in channels and laboratories. In this thesis, numerical modelling technique was used in the solution of two flow measurement problems, namely contracted sharp crested weirs (Problem 1) and combined weir and gate system (Problem 2). The numerical simulation of flow cases having similar conditions with the experiments from the previous studies is performed for both Problem 1 and 2. The basic flow...
Citation Formats
S. GHARAHJEH, İ. Aydın, and A. B. Altan Sakarya, “Weir velocity formulation for sharp-crested rectangular weirs,” FLOW MEASUREMENT AND INSTRUMENTATION, pp. 50–56, 2015, Accessed: 00, 2020. [Online]. Available: