عنوان مقاله [English]
Comparing Hydraulics Parameter Between Half Cycle cosine weirs and Rectangular weirs
Abstract: Weirs are widely used in agricultural and hydraulic engineering for measuring and regulating flow. The various shapes of weirs give rise to their special characteristics. One of the Weirs problems in irrigation system is changing hydraulic characteristics when upstream the weirs filled by sediments. This study introduces a novel sharp-crested weir design with a cosine weirs, and investigates physical models of cosine sharp-crested weirs of different widths. The analysis aims to establish the head discharge relationship and to inspect velocity distribution and the hydrodynamic characteristics of flow in the vicinity of the weir plate. The hydraulic behavior of cosine weirs is also compared with that of rectangular sharp-crested weirs. The results show that the secondary currents and the turbulence intensity in the vicinity of the cosine weirs are stronger than those of rectangular weirs. Also, turbulence intensity rise side wall cosine weirs more than the rectangular weirs. Therefore, this type of weir can provide an efficient passage and wash sediment behind the weirs.
Weirs are commonly used in water engineering to raise the upstream water level to increase water storage and irrigation capacity, and to enable navigation. Weirs increase the upstream total head benefitting the generation of hydroelectricity. Weirs are also commonly used as flow control structures, which allow the measurement of flow discharges via flow depth since the flow passes through critical flow depth on the weir crest.
Sharp-crested weirs of diverse shapes are used in irrigation and hydraulic engineering for measuring flow. The shape of weirs are different forms, such as rectangular, triangular, and trapezoidal. The hydraulic behavior of these types of weirs has been extensively investigated
Weirs with more complicated shapes, such as circular, parabolic, proportional, logarithmic, and quadratic, have also received considerable attention.
Key Words: Cosine weirs, Acoustic Doppler Velocity, Confection Discharge, Turbulence Intensity