The Effect of Height and Crest Slope of the Submerged Weirs on Erosion and Sedimentation Pattern in a 〖90〗^o Sharp Bend

Document Type : Research Paper


1 Department of Water Engineering, faculty of agriculture and natural resources, Urmia University, Urmia, Iran

2 Department of Water Engineering, faculty of irrigation and natural resources, Urmia University, Urmia, Iran

3 Department of Irrigation and Reclamation Engineering, faculty of agricultural engineering and technology, University of Tehran, Karaj, Iran

4 Department of Civil, Environmental , and Architectural Engineering ICEA, faculty of engineering, University of Padua, Padua, Italy.


Submerged weirs are short-height structures that are completely beneath the water surface and are constructed to improve shipping conditions, create aquatic habitats, control the movement of bends, etc. The purpose of this study was to evaluate the patterns of erosion and sedimentation at a 90o sharp bend. To achieve this goal, a series of weirs with the relative heights of 30% and 70% and crest slopes of 0 and 7% were constructed on the outer wall of the bend. The angle, length, and distance between weirs were kept constant. The results showed that bendway weirs with a relative height of 70% and a flat crest slope had the best performance in protecting the bed near the outer bend wall. With the construction of these structures in the bend, 7% of sedimentation was done near the outer wall at a cross-section corresponding to the maximum scour location in the unstructured state. Changes in the height and crest slope of the bendway weir did not have a significant effect on reducing the maximum relative height of point-bar, and only at Froude number of 0.43 the average maximum relative point-bar height decreased by 10%. Moreover, with increasing the height and crest slope of the weirs, the maximum relative scours depth at the nose of the third weir increased by 11% and decreased by 6%, respectively.


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