Computational study of flow structure and forces on a cylinder vibrating transversely and in-line to a steady stream: Effects of subharmonic forcing

Perdikaris, PG; Kaiktsis, L; Triantafyllou, GS

dc.contributor.author	Perdikaris, PG	en
dc.contributor.author	Kaiktsis, L	en
dc.contributor.author	Triantafyllou, GS	en
dc.date.accessioned	2014-03-01T02:52:37Z
dc.date.available	2014-03-01T02:52:37Z
dc.date.issued	2010	en
dc.identifier.issn	0277027X	en
dc.identifier.uri	https://dspace.lib.ntua.gr/xmlui/handle/123456789/35960
dc.relation.uri	http://www.scopus.com/inward/record.url?eid=2-s2.0-77953086481&partnerID=40&md5=96f9abb58f1c8955eab9b6b4c608f580	en
dc.subject.other	Computational studies	en
dc.subject.other	Counter-clockwise	en
dc.subject.other	Cylindrical structure	en
dc.subject.other	Excitation amplitudes	en
dc.subject.other	Flow properties	en
dc.subject.other	High amplitudes	en
dc.subject.other	In-line	en
dc.subject.other	In-line oscillations	en
dc.subject.other	Power transfers	en
dc.subject.other	Regular patterns	en
dc.subject.other	Research teams	en
dc.subject.other	Resonant forcing	en
dc.subject.other	Spectral element method	en
dc.subject.other	Sub-harmonic excitation	en
dc.subject.other	Subharmonics	en
dc.subject.other	Transverse frequency	en
dc.subject.other	Transverse oscillation	en
dc.subject.other	Transverse vibrations	en
dc.subject.other	Vortex induced vibration	en
dc.subject.other	Vortex pattern	en
dc.subject.other	Vortex street	en
dc.subject.other	Boilers	en
dc.subject.other	Caissons	en
dc.subject.other	Flow structure	en
dc.subject.other	Flow visualization	en
dc.subject.other	Harmonic analysis	en
dc.subject.other	Hydraulics	en
dc.subject.other	Pressure vessels	en
dc.subject.other	Reynolds number	en
dc.subject.other	Roads and streets	en
dc.subject.other	Wakes	en
dc.subject.other	Cylinders (shapes)	en
dc.title	Computational study of flow structure and forces on a cylinder vibrating transversely and in-line to a steady stream: Effects of subharmonic forcing	en
heal.type	conferenceItem	en
heal.publicationDate	2010	en
heal.abstract	In this work, we present a computational study of the flow structure and forces on a cylinder vibrating both transversely and in-line to a uniform stream. The in-line frequency is equal to twice the transverse frequency, while the ratio of the in-line to the transverse oscillation amplitude varies from zero (transverse vibration only) to infinity (in-line oscillation only). For all intermediate values, the cylinder thus follows an ""eight ""-like of trajectory, emulating the motion of real cylindrical structures undergoing vortex-induced vibrations. For a flow from left to right, we distinguish between a ""counter-clockwise"" mode (if the upper part of the trajectory is traversed counter-clockwise) and a ""clockwise "" mode (if the upper part of the trajectory is traversed clockwise). Here, we use a spectral element method, and perform simulations for a Reynolds number of 400. We focus on a value of the transverse oscillation frequency equal to half the natural frequency of the Kármán vortex street (sub-harmonic excitation). Results are compared against cases corresponding to resonant forcing, previously studied by the research team. In all cases, the flow properties are greatly influenced by the direction in which the cylinder is traversed. In particular, the ""counter-clockwise"" mode is characterized by higher values of the forces acting on the cylinder, as well as by higher values of the power transfer from the flow to the cylinder. The case of sub-harmonic excitation is unique, in that the power transfer remains negative for all values of the non-dimensional excitation amplitude, i.e. corresponds to damping. Flow visualization reveals a variety of vortex patterns in the wake, in particular regular patterns at sub-harmonic excitation, and complex vortex streets at high amplitude resonant forcing. Copyright © 2009 by ASME.	en
heal.journalName	American Society of Mechanical Engineers, Pressure Vessels and Piping Division (Publication) PVP	en
dc.identifier.volume	4	en
dc.identifier.spage	475	en
dc.identifier.epage	479	en