Discharge formula for rectangular sharp-crested weirs

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, when the weir is operated within an appropriate discharge range. Average velocity over the weir plotted against the weir head displays universal characteristics such that it can be used in the expression of discharge over the weir, eliminating the need for a discharge coefficient. The head-discharge relationship for a rectangular weir has distinct features for the partially contracted weirs and for the fully contracted slit weirs.


Weir velocity formulation for sharp-crested rectangular weirs
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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 geo...
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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...
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Şişman, H. Çiğdem; Altan Sakarya, Ayşe Burcu; Department of Civil Engineering (2009)
Sharp crested rectangular weirs used for discharge measurement purposes in open channel hydraulics are investigated experimentally. A series of experiments were conducted by measuring discharge and head over the weir for different weir heights for full width weir. It is seen that after a certain weir height, head and discharge relation does not change. Hence a constant weir height is determined. For that height; discharge and head over the weir are measured for variable weir width, starting from the full wi...
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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...
Citation Formats
İ. Aydın and A. B. Altan Sakarya, “Discharge formula for rectangular sharp-crested weirs,” FLOW MEASUREMENT AND INSTRUMENTATION, pp. 144–151, 2011, Accessed: 00, 2020. [Online]. Available: https://hdl.handle.net/11511/41871.