Abstract
Design of water structures and their segments including spillways play an important role in water resources management and agricultural activities. In the the linear body part of an ogee spillway, for speeding up the flow rate, the flow should be transferred to the stilling basin by inverse curve so that the water energy can be reduced. This study aims to evaluate the effect of the inverse profile curvature on the pressure of spillway surface using Fluent software. For this purpose, five different curvatures of inverse profile were considered to be equal to no-curvature (zero), 1, 1.5, 2 and 2.5 of the spillway design head. The results indicated that by increasing the curvature radius, the maximum pressure dramatically reduced. And for this purpose, some relationships were given to predict the pressure reduction. Pressure increment in zero curvature is caused by sudden collision of flow lines and turbulence caused by it. By increase in inverse profile curvature, the turbulence is created in flow lines and the maximum pressure shows a lower value than before. In general, there was little change in the average absolute pressure.
Highlights
Ogee spillway is one of the most common yet the least expensive spillways which can pass large amount of water
The flow behavior on the ogee spillway is numerically simulated. 2 dimentional numerical simulation was performed by Fluent software, and turbulence model of RNGk-ε was used for modeling turbulences in the flow
A dimensionless number was considered for introducing the inverse curvature of the arc which is the ratio of curvature radius to the spillway design (r/Hd)
Summary
Ogee spillway is one of the most common yet the least expensive spillways which can pass large amount of water. One of the important segments of these spillways that was less investigated by researchers is the inverse curvature at the end of the ogee spillway which transfers the flow on the spillway profile to the stilling basin. These spillways are often used in diversion weirs due to high hydraulic efficiency. Maynord (1985) examined a simple way to design the ogee spillway crest curve He measured the discharge coefficient and static pressure on the crest as well as the water surface profile both with and without base, and presented their results in graphs and tables.
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