Experimental study of two phase Air-water Flow Parameters in Hydraulic Jumps with vegetated Rough Bed

Document Type : Research Article

Authors

1 Faculty of Water and Environmental Engineering,, Department of Hydraulic Structures, Shahid Chamran University of Ahvaz.

2 Associate Professor. Faculty of Water and Environmental Engineering, Department of Hydraulic Structures, Shahid Chamran University of Ahvaz

3 Professor. Faculty of Water and Environmental Engineering, Department of Hydraulic Structures, Shahid Chamran University of Ahvaz

Abstract

Hydraulic jumping is a complex three-dimensional phenomenon which is frequently observed in open channel flow such as rivers. The hydraulic resistance of vegetation plays a major role in the hydrodynamics of rivers with extensive natural floodplains. Vegetation penetrates the flow field and creates resistant force and, consequently, energy dissipation. In this study, the effect of vegetation density and height on flow in a hydraulic jump and parameters related to two phase Air-water flow are examined using cylindrical elements made of galvanized iron with a homogeneous diameter of 7 mm as vegetation. Thus, neither the effects of plant diversity nor flexibility have been considered. For this purpose, four forms of rough bed were used in two modes of staggered and collocated grid roughness with two heights of 1.5 and 3 cm, and the results were compared with data on smooth bed as a reference. Experiments were conducted in a horizontal rectangular flume with a width of 30 cm, in the range of upstream Froude numbers between 1.5 Fr1 5.5. Air-water flow measurements were conducted with a dual-tip conductivity probe, which was designed, developed and calibrated in this research. The results of this study showed that the presence of vegetation increases aeration by increasing the void fraction in a jump roller. And on the other hand, increasing the resistant force and shear stress in the bed reduces conjugate depths and roller length. This increase and decrease depends on the upstream Froude numbers, height and density of vegetation.

Keywords

References

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Iranian journal of Ecohydrology
Volume 8, Issue 3
October 2021
Pages 763-775

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History

  • Receive Date: 22 May 2021
  • Revise Date: 28 August 2021
  • Accept Date: 16 August 2021

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