Numerical investigation of arced sharp crested weirs

Ebrani, Nazli (2017) Numerical investigation of arced sharp crested weirs. Masters thesis, University of Mohaghegh Ardabili.

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Abstract

Weirs are used for passing flood in dams.Arced weir is a part of a circle that increases the crest length for a given channel width that increases the discharge capacity of the existing spillways. In this research, first the modeling of arced sharp crested weir in different degrees and heads with Flow3D was done. To validate carried out numerical modeling , agreement of discharge coefficient obtained from simulations compared with experimentally results. In the next step ,by adding a straight length to the side of first models , the effect of upstream head on hydraulic Performance of arced weirs investigated by drawing stramlines in different levels and flow pattern .Exclusively , The results indicate this , which Best option to increase performance of straight sharp-crested spillway (0 degree) in lower flow heads is adding side length to this weir ,which In addition to increasing the flow capacity, Increases the discharge coefficient In the optimal way and improves the distribution of the side lines of the reservoir in the corners of this weir. On the contrary Adding long side length to arced weir with a high angle arc (180-degree) has No significant impact on spillway performance and actually, will impose additional costs on the executive. In general, similar to hydraulic of arced weirs Increasing the angle of the arced spillway with straight wing faces Increases the dimensions of the flow stack phenomenon and reduces the discharge coefficient and overflow efficiency.

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