Experimental study of the effect of jump on the Downstream Scouring of type-C trapezoidal piano key weir

Document Type : Research Article

Authors

1 Faculty of Civil Engineering, Islamic Azad University of Isfahan (Khorasgan), Isfahan, Iran

2 civil engineering department, Islamic azad university, Isfahan branch

3 Faculty of Civil and Environmental Engineering, Tarbiat Modares University, Tehran, Iran

Abstract

Piano key weirs (PKWs) represent an evolved and novel type of labyrinth weirs, offering a higher discharge coefficient when compared to linear weirs. Recent attention has focused on investigating energy loss and downstream scouring associated with piano key weirs, given their high efficiency and potential for reducing financial and life risks. In this research, a type-C trapezoidal piano key weir with a height of 0.2 m was utilized, incorporating two jumps with radii of 0.15 and 0.21 m at the weir outlet keys. After setting the flow rate and the tailwater, scouring was started, and then after the equilibration time, the pump was turned off after complete drainage, and the bed profile was taken by a laser meter. The findings indicated that the presence of a jump contributes to an increase in maximum scour depth. Furthermore, the presence of a jump causes the maximum scouring depth to occur further away from the weir toe. Increasing the radius of the jumps also results in an augmented maximum scour depth. The length of the maximum scour depth, compared to the weir toe, is approximately 12% greater in weirs with a bigger jump radius than those with a smaller radius. On average, the maximum length of the scour depth about the weir toe is 29.4% and 19.5% longer in weirs with jump radii of 0.21 and 0.15 m, respectively, compared to weirs without jumps. Additionally, the presence of a jump diminishes scouring at the weir toe, with toe scour being approximately 42% less pronounced in weirs with a bigger jump height compared to weirs without jumps. The average scour index in weirs with jump radii of 0.21 and 0.15 m is approximately 2.77% and 0.52% lower, respectively, compared to weirs without jumps. Moreover, an increase in jump radius correlates with a decrease in the discharge coefficient.

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References

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Amirkabir Journal of Civil Engineering
Volume 56, Issue 11
2025
Pages 1353-1368

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