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The influence of edge undulation on vortex formation for low-aspect-ratio propulsors

Kaiser, Frieder; Kriegseis, Jochen; Rival, David E.

Abstract (englisch):
Experiments to study the effect of edge undulation on vortex formation have been conducted on impulsively accelerated plates. Abstractions of propulsors found in nature are produced by imprinting undulatory features with varying wavelengths onto the circumferential vortex-forming edge of circular plates. The effects of the small-scale disturbances introduced by these modifications are accessed by means of force measurements and time-resolved particle image velocimetry. Investigations of four different geometries at two different Reynolds numbers reveal an insensitivity of the flow towards length scales smaller than or similar to the thickness of the feeding shear layer. However, the instabilities in the shear layer and the coherence of the vortex wake are influenced when the wavelength of the undulation exceeds the shear-layer thickness by a significant margin. This results in a force augmentation due to enhanced entrainment into the turbulent vortex core, and thus an associated faster vortex growth rate. Yet, contrary to prior expectations, the time of vortex pinch-off remains constant for all edge modifications. The cause–effect relationship behind the stability of the vortex wake is further investigated. ... mehr

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Verlagsausgabe §
DOI: 10.5445/IR/1000100367
Veröffentlicht am 29.01.2020
Cover der Publikation
Zugehörige Institution(en) am KIT Institut für Strömungsmechanik (ISTM)
Publikationstyp Zeitschriftenaufsatz
Publikationsmonat/-jahr 01.2020
Sprache Englisch
Identifikator ISSN: 0022-1120, 1469-7645
KITopen-ID: 1000100367
Erschienen in Journal of fluid mechanics
Band 883
Seiten Art. Nr.: A55
Vorab online veröffentlicht am 29.11.2019
Schlagwörter propulsion, free shear layers, mixing enhancement
Nachgewiesen in Scopus
Web of Science
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