Puria Asiaban; Manoochehr Fathi Moghadam; Sajad Kiani; Ahmad Hosseini
Abstract
Rectangular orifices are considered as a common structure for discharge measurement in hydraulics. The purpose of the present research is to investigate the effect of the ratio of length to width of rectangular orifices with same surface area on discharge coefficient. Different rectangles are examined ...
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Rectangular orifices are considered as a common structure for discharge measurement in hydraulics. The purpose of the present research is to investigate the effect of the ratio of length to width of rectangular orifices with same surface area on discharge coefficient. Different rectangles are examined as orifice while the aspect ratio in one of them is equal to 1.618 (golden ratio). Golden ratio is a special number which can be frequently existed in nature and this study attempts to find the probable specialty of this ratio in hydraulics. So, the experiments were carried out on five rectangle orifices that the ratio of length to width of ones varied from 1 to 16. Also, a comparison between the discharge coefficient of rectangular and circular orifices is performed. Therefore, the number of 94 tests was conducted on the orifices in the discharge range of 0.136 - 0.637 L/s. A mathematical relation is developed as pressure distribution coefficient in order to account the effect of non-hydrostatic pressure distribution under low head condition. Results of the experiments showed that the increasing of aspect ratio generally leads to increase discharge coefficient so that discharge coefficient of orifices with variation of the ratio of length to width changes about 11.7%. Furthermore, it is illustrated that golden ratio doesn’t have any specialty in flow evacuation and the discharge coefficient of circular orifices is equal to minimum discharge coefficient of rectangular orifices.
Sajad Kiani; Salah Kouchakzadeh; Seyed Ahmad Hosseini
Abstract
The ogee spillway with an arc plan has a longer crest length. Therefore, in a specific reservoir water level, it can discharge higher flow rate compared to a straight one and due to this reason is preferred in applicable plans. The aim of this research was to laboratory investigation on the effect of ...
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The ogee spillway with an arc plan has a longer crest length. Therefore, in a specific reservoir water level, it can discharge higher flow rate compared to a straight one and due to this reason is preferred in applicable plans. The aim of this research was to laboratory investigation on the effect of the curvature of the ogee overflow weir on distribution of flow discharge, determination of discharge coefficient and study the overall hydraulic behavior. This research was executed on Germichai Dam spillway physical model which was constructed in the Soil Conservation and Water Management Research Institute hydraulic lab. Results showed the need of correction on initial design and that the discharge coefficient of this free overflow is nine percent in average, less than ogee spillways with straight axis On the other hand, the geometry of the downstream conveyance conduit forces the spillway to act in a submerged condition for discharges higher than 1.3 times the design discharge And the discharge coefficient presented a decreasing trend with the upstream weir head.
