Abstract
The present research describes a laboratory study of hydraulic jump in the abrupt asymmetric expansion stilling basin as an energy dissipator by changing the geometry of walls and bed roughness elements. The experiments were carried out in a horizontal flume with 10 m length, 0.5 m width, and 0.5 m depth for a range of the upstream Froude numbers ( F r 1 ) from 5 to 11. Four physical models with expansion ratio of α = 0.33, 0.5, 0.67, and 1 and asymmetry ratio of Δ = 0.16 were installed in the flume and two different heights of roughness elements ( h = 1.4 and 2.8 cm) were also considered. The results indicated that the sequent depth and the jump length as well as the roller length below abrupt asymmetric expansion on the rough bed were decreased in comparison to the same parameters of the jump in a prismatic channel with smooth bed. It was revealed that the roughness elements have the effective role on stabilization of the hydraulic jump location. The analysis of energy dissipation efficiency confirmed that the spatial jump in the abruptly expanded basin with roughened bed was more efficient than classical jump. In order to estimate the hydraulic jump characteristics, empirical relationships associated with expansion ratio of basin walls, relative height of roughness elements and upstream Froude number were proposed based on the experimental data that resulted in preliminary design of an abrupt asymmetric enlarged basin.
Highlights
A Hydraulic jump as a rapidly-varied flow describes a sudden transition from a supercritical flow to a subcritical flow through a strong energy dissipative mechanism [1]
(17)Ratio indicates that the ratio of y2 /y1 depends on the upstream Froude number (Fr1 ), the relative roughness height
Figure that in the all research in sudden symmetric expanding channels, the results showed that the asymmetry of expansion the decreased sequent depth on depth the rough bedItwere compared classical expandingratios, channel the ratios sequent ratio
Summary
A Hydraulic jump as a rapidly-varied flow describes a sudden transition from a supercritical flow to a subcritical flow through a strong energy dissipative mechanism [1]. A hydraulic jump dissipates the excess kinetic energy of the flow through turbulence and converts it into energy. A hydraulic jump is extensively used in hydraulic engineering applications as an energy dissipator below chutes, weirs, gates, and spillways to protect downstream from severe scouring and possible destruction. Perhaps the oldest basic experimental and scientific research about hydraulic jumps was carried out by Bélanger (1828). He was the first researcher who applied continuity and momentum principles in a smooth horizontal prismatic channel to estimate sequent depth ratios [3]: y∗2
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