Abstract
Sharp-crested weir and side-channel weirs can be considered among the control and flow-measuring structures which are greatly applicable in channels, dam spillways and other hydraulic structures. Discharge coefficient in these two types of weirs is affected by the structural geometry and the hydraulics of the flow. Suspended load is one of the main factors which may affect the hydraulics of the flow and consequently modify the flow discharge coefficient. Using different geometrical and hydraulic conditions, the discharge coefficient relation in sharp-crested and side channel weirs for the case of suspended load can be extracted. Flow3D numerical model is capable of precisely simulation the flow containing suspended and bed load in the main channel. The discharge coefficient equation is deduced and presented based on the Froude number, by numerical iterations. The numerical results reveal that the discharge coefficient in the two cases of clear water and the flow containing suspended load are totally different. At the same hydraulic load, the discharge coefficient in the case of existing suspended load is greater than the case of clear water; In addition, the discharge coefficient is reduced by increasing the Froude number in all cases with different load concentrations.
Highlights
The weir is defined as an obstacle which is put in front of the flow and makes the water to rise at the back side of the weir
Since the hydraulic theory relevant to this weir is considered as the main base for designing the other types of weirs, the sharp-crested weirs are considered to be of great importance
The results show that in both structures, the discharge coefficient is affected by the flow suspended load, e.g. decreased by the suspended load increase [9]
Summary
The weir is defined as an obstacle which is put in front of the flow and makes the water to rise at the back side of the weir. By the study of the suspended load effect on the velocity profile in a flume with the two conditions of smooth and rough beds, Kereselidze and Kutavaia (1995) realized that the velocity in the smoothed bed flume is decreased close to the bed and increased near the free surface and the suspended load carrying flow average velocity in the smoothed bed flume may be smaller than, equal to or greater than the clear water flow velocity. The results show that in both structures, the discharge coefficient is affected by the flow suspended load, e.g. decreased by the suspended load increase [9] As it was observed earlier, the diversity of side-channel and sharp-crested weirs and different sediment types has caused the experimental study to be time consuming and costly. The flow over sharp-crested and side-channel weirs has been investigated and and turbulence models have been used for the turbulence field
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