Investigation of Hydraulic Jump Characteristics on Rough Bed with Different Density and Arrangements of Roughness Elements

Document Type : Research Paper

Authors

Abstract

Hydraulic jump is a rapidly varied flow in open channels which performs an effective role in dissipation of the kinetic energy of flow at downstream of water structures. In the present study the characteristics of hydraulic jump, including sequent depth, energy dissipation, bed shear stress and velocity profiles at different sections, on rough bed with discontinuous roughness elements of lozenge shape have been investigated. The experiments were carried out for a range of Froude number values from 4.3 to 12.4 in three roughness densities and four combined arrangements of roughness elements. The results of this study showed that the velocity profiles on rough beds were similar but somehow different from those of wall jet on smooth bed. The dimensionless boundary layer thickness was 0.53 on rough bed that was more than corresponding value on smooth bed with the amount of 0.16. As the roughness density increased the bed shear stress produced by the interaction of upstream supercritical flow with the roughness elements enhanced so the energy loss increased and as a result the sequent depth decreased. In the arrangement of ternary combination of roughness elements with density of 10.67 % the maximum reduction value of the sequent depth was about 29.39%, the increase of the energy dissipation relative to hydraulic jump on smooth bed was10.94% and the bed shear stress coefficient on rough bed was about 13.54 times as much as its corresponding value on smooth bed.

Keywords

Main Subjects

References

نیسی ک و شفاعی بجستان م، 1388. بررسی عمق مزدوج پرش هیدرولیکی تحت تاثیر اجزای زبر کف. نشریه دانش آب و خاک، جلد19،شماره2، صفحه­های  165تا 176.
Ead SA and Rajaratnam N, 2002. Hydraulic jump on corrugated bed. Journal of Hydraulic Engineering ASCE 128(7): 656-663.
Hughes WC and Flack JE, 1984. Hydraulic jump properties over rough bed. Journal of Hydraulic Engineering ASCE 110(12): 1751-1771.
Mohammad Ali HS, 1991. Effect of roughened-bed stilling basin on lengh of rectangular hydraulic jumps. Journal of Hydraulic Engineering ASCE 117(1): 83-93.
Nasr Esfahani MJ and Shafai Bejestan M, 2012. Design of stilling sasins using artificial roughness. Journal of Civil Engineering 2(4): 159-163.
Rajaratnam N, 1965. The hydraulic jump as a wall jet. Journal of Hydraulic Division ASCE 91(5): 107-132.
Wang H, Felder S and Chanson H, 2014. An experimental study of turbulent two-phase flow in hydraulic jumps and application of a triple decomposition technique. Journal of Experimental Methods and Their Applications to Fluid Flow 55(1775): 1-18.

Files

Share

How to cite

Statistics