Hydraulic jump aeration and turbulent dissipation on beds roughened by rigid and flexible vegetation

This study examines the aeration and turbulence characteristics of hydraulic jumps over vegetated rough beds. Three vegetation types including rigid acrylic rods, artificial turf and multi-leaf flexible plants were tested for Froude numbers between 2.8 and 5.5, with controlled equivalent roughness heights. Phase-detection probe measurements showed that all vegetated beds increased pre-aeration and impingement air entrainment at the jump toe. Vegetation morphology affects air–water flow properties more than vegetation density, especially at low Froude numbers. Flexible vegetation induced distinct turbulence modulation via shear layer interaction, despite lower flow resistance compared to rigid or turf-type roughness. The streamwise decay of characteristic void fraction, bubble count rate and velocity values are noted to be influenced by both approach flow conditions and vegetation dynamic response.