Air–water flow properties in hydraulic jumps on rough pebbled bed

ABSTRACT

In open channel flows, a hydraulic jump is a rapid shift from a supercritical flow to a subcritical flow with a sharp rise in the elevation of the free surface, which is associated with strong energy dissipation, air entrainment, and spray. The present research aims to investigate the air–water flow properties in a hydraulic jump on rough pebbled bed. A range of discharges from 0.06 to 0.1 m³/s, corresponding to inflow Froude numbers Fr₁ between 1.7 and 2.84 and Reynolds numbers Re₁ from 140,000 to 220,000 were considered. The basic parameters of two-phase flow such as the void fraction and bubble count rate are presented. Close to the jump toe, the mean void fraction on rough bed was larger than on smooth bed, while farther downstream larger magnitudes were observed on smooth bed. No significant difference was observed between rough and smooth beds in terms of the maximum void fraction. In the turbulent shear layer, the bubble count rate was comparatively larger on rough bed than on smooth bed, while the longitudinal distribution decayed for both bed configurations.

KEYWORDS:

• Hydraulic jump
• rough pebbled bed
• air–water flow
• two-phase flow

Acknowledgments

The authors thank Jason Van Der Gevel and Stewart Matthews for their technical assistance at the Hydraulic Laboratory of The University of Queensland. Farhad Bahmanpouri acknowledges the financial support from the University of Napoli Federico II (PhD Program in Civil Systems Engineering).

Disclosure statement

No potential conflict of interest was reported by the author(s).