Effect of Roughness Shape on the Sequent Depth Ratio of Hydraulic Jump

Document Type : Research Paper

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Abstract

In this study, the effect of shape of roughness elements on the bed shear stress and sequent depth of hydraulic jump have been investigated. Experiments are conducted in a rectangular flume 0f 7.5 m long and 0.3 m wide in the hydraulic laboratory of ShahidChamranUniversity, Ahwaz, Iran. For the purpose of this study, prismatic roughness elements with different shapes: rectangular, triangular, circular, lozenge and hexangular were tested. The roughened elements are glued on the bed of flume downstream of ogee spillway in such a way that the incoming water jet is just above the element surface. The incoming Froude number was in the range of 4.5 to 12. During each tests the water surface profile, the roller length and the jump length were measured. In few tests the longitudes and vertical flow velocity were measured. The results indicated that the presence of rough elements can reduce the sequent depth ratio.  The amount of reduction would depend on the Froude number and the roughness shape. The triangular element can produce lesser sequent depth ratio.  Relations have been presented in this study for the sequent depth of hydraulic jump and shear force coefficient of bed as a function of the Froude number for each roughness shape.

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References

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Water and Soil Science
Volume 19, Issue 1
May 2009
Pages 165-176

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