Author(s): Mouldi Ben Meftah; Francesca De Serio; Diana De Padova And Michele Mossa
Linked Author(s): Mouldi Ben Meftah, Francesca De Serio, Diana De Padova, Michele Mossa
Keywords: Partly vegetated channel emergent vegetation ADV velocity turbulence dynamic contraction ratio
Abstract: In this study, we attempt to experimentally investigate the flow turbulence structure and the discharge prediction in a partly vegetated channel with emergent rigid vegetation. Various configurations were tested, varying the contraction and aspect ratios. The contraction ratio is defined as the ratio of the width of the vegetated area to the width of the unvegetated area. In contrast, the aspect ratio is defined as the ratio of the flow depth to the width of the unvegetated area. The experiments were conducted in a large channel at the Coastal Engineering Laboratory of the Department of Civil, Environmental, and Building Engineering and Chemistry at the Polytechnic University of Bari, Italy. The instantaneous flow velocity components were accurately measured using a 3D Acoustic Doppler Velocimeter (ADV) -Vectrino system at high frequency. Flow behavior through the vegetated area, at the interface, and in the non-vegetated area was analyzed via time-averaged field velocity distribution, turbulent intensity, turbulent kinetic energy, correlation properties, spectral analysis, and vortex identification. Special attention is given to understanding the effect of the contraction ratio on the flow dynamic structures. Experimental results showed the development of three distinct characteristic flow zones: (i) a vegetated area with low streamwise velocity, high turbulence intensities, an intense power spectrum, and dominant inward interactions; (ii) a shear layer zone with increasing streamwise velocity, enhanced transverse flow motion, a significant decrease in turbulence intensities, and frequent ejection and/or outward interaction events; and (iii) a free-stream zone with higher and almost constant streamwise velocity, lower turbulence intensities, frequent sweep and/or inward interaction events, and a less intense streamwise power spectrum. The experimental results also show a considerable effect of the contraction ratio on the flow dynamic structures.
Year: 2025