Reference : Nappe Vibration Mitigation Techniques for Free-overfall Structrures
Scientific congresses and symposiums : Paper published in a book
Engineering, computing & technology : Civil engineering
Nappe Vibration Mitigation Techniques for Free-overfall Structrures
Lodomez, Maurine mailto [Université de Liège > Département ArGEnCo > HECE (Hydraulics in Environnemental and Civil Engineering) >]
Crookston, Brian M. mailto [> >]
Tullis, Blake P. mailto [> >]
Pirotton, Michel mailto [Université de Liège > Département ArGEnCo > HECE (Hydraulics in Environnemental and Civil Engineering) >]
Erpicum, Sébastien mailto [Université de Liège > > Scientifiques attachés au Doyen (Sc.appliquées) >]
Full Proceedings: Hydraulic Structures and Water System Management
6ᵗʰ International Symposium on Hydraulic Structures
du 27 juin 2016 au 30 juin 2016
International Association for Hydro-Environmental Engineering and Research and United States Society on Dams
[en] nappe vibration ; nappe oscillation ; physical modelling ; spillway ; flow acoustics
[en] Nappe vibration is a phenomenon that has been witnessed in the field for a variety of different free overflow hydraulic structures operating at low heads, such as fountains, crest gates, and weirs. This phenomenon is visually characterized by oscillations in the thin nappe cascading downstream of the control structure. These oscillations can produce a significant level of noise and acoustic pressure waves, which can increase the environmental and societal impacts of the hydraulic structure. As a result, a detailed investigation has been undertaken to identify practical and effective mitigation solutions for free-overfall structures where nappe vibration may be of concern. Research is being performed with a prototype-scale linear weir (weir length of 3.5 m and fall height of 3 m) located at the Engineering Hydraulics laboratory of the University of Liège, to assess the effectiveness of various crest modifications and any corresponding impacts to hydraulic efficiency (i.e., flow rate). The test matrix includes the optimization (position and spacing of elements) of three mitigation solutions which are projecting bolts, deflectors and step. In addition, a high-speed camera and audio equipment have been used to evaluate effectiveness of the configurations in reducing nappe vibration. Finally, this practical study has identified countermeasures suitable for retrofits and new construction, easy to construct, durable, hydraulically efficient, and with minimal potential for debris collection.

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