The quasi-steady assumption is frequently employed to derive the fluid dynamic forces on an oscillating body in fluidelastic stability analysis. Although it is well accepted, and physically reasonable, that this assumption is valid for high values of non-dimensional flow velocity, $U/fD,$ and invalid for low values, it is still uncertain how the error varies with $U/fD.$ In this thesis the applicable range of the quasi-steady assumption and the error of the assumption are investigated experimentally for three cases of two staggered circular cylinders in cross-flow. The applicable range is presented in terms of $U/fD,$ reduced frequency $fD/U$ or the ratio of the vortex-shedding frequency on the stationary model to the frequency of oscillation, $f sbsp{v}{s}/f.$ / Two quasi-steady models are studied, a basic model and a modified model. The basic model allows fluid force coefficients measured on a stationary body to be used to determine the fluidelastic forces on an oscillating body, provided that the body motion is correctly accounted for in the resultant velocity vector. The modified model takes the following into account also: (i) the magnitude and incidence of the flow velocity approaching the oscillating cylinder, and (ii) the time delay between cylinder displacement and the fluidelastic forces generated thereby. / Forced vibration measurements are conducted for the three cases. In each case one cylinder is forced to oscillate in the cross-flow direction and the other is fixed. The fluidelastic forces on the oscillating cylinder in the cross- and in-flow directions are measured over a wide range of $U/fD$ (roughly $5f/f sbsp{v}{s}>1.1$, where the quasi-steady assumption totally breaks down.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.39892 |
| Date | January 1995 |
| Creators | Wang, Da-Jun |
| Contributors | Price, S. J. (advisor), Paidoussis, M. P. (advisor) |
| Publisher | McGill University |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Format | application/pdf |
| Coverage | Doctor of Philosophy (Department of Mechanical Engineering.) |
| Rights | All items in eScholarship@McGill are protected by copyright with all rights reserved unless otherwise indicated. |
| Relation | alephsysno: 001473572, proquestno: NN08166, Theses scanned by UMI/ProQuest. |
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