Vortex Shedding and Modal Behavior of a Circular Cylinder Equipped with Flexible Flaps
When a cylinder is subject to a flow, vortices will be shed that can lead to strong tonal noise. The modification of the cylinder with soft, flexible flaps made of silicone rubber has been shown to affect the vortex shedding cycle in a way that the Strouhal number associated with the vortex shedding suddenly jumps to a higher value at a certain Reynolds number. In the present study, the effect of the flexible flaps on the vortex shedding is further examined by subsequently reducing the number of flaps and additionally shortening their length. Acoustic measurements and camera recordings of the flap motion, performed in an aeroacoustic wind tunnel, suggest that the sudden jump of the Reynolds number is caused by the movement of the outer flaps. A comparison with the eigenfrequencies obtained from a numerical modal analysis of the different flap rings revealed that the cause of the Strouhal number jump is most likely a lock-in of the natural vortex shedding cycle with the next higher eigenfrequency of the outer flaps.
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Document Type: Research Article
Publication date: January 1, 2019
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- Acta Acustica united with Acustica, published together with the European Acoustics Association (EAA), is an international, peer-reviewed journal on acoustics. It publishes original articles on all subjects in the field of acoustics, such as general linear acoustics, nonlinear acoustics, macrosonics, flow acoustics, atmospheric sound, underwater sound, ultrasonics, physical acoustics, structural acoustics, noise control, active control, environmental noise, building acoustics, room acoustics, acoustic materials, acoustic signal processing, computational and numerical acoustics, hearing, audiology and psychoacoustics, speech, musical acoustics, electroacoustics, auditory quality of systems. It reports on original scientific research in acoustics and on engineering applications. The journal considers scientific papers, technical and applied papers, book reviews, short communications, doctoral thesis abstracts, etc. In irregular intervals also special issues and review articles are published.
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