The main aim of this thesis is the study of the two mechanisms underlying fluidelastic instability in cylinder arrays subjected to cross-flow: the negative fluid damping and the fluid stiffness-controlled mechanisms, especially with regard to the effect of fluidelastic coupling between cylinders and the effect of system parameters in each case. / An in-line square array with pitch-to-diameter ratio P/d = l.5 has been tested in both water- (with low mass ratio, $m/pd sp2$ = 6.5) and air-flow (with high mass ratio, $m/pd sp2$ = 860). The effect of fluidelastic coupling between cylinders on the critical flow velocity for fluidelastic instability was investigated via frequency detuning experiments, including an extreme case of one flexible cylinder in an otherwise rigid cylinder array. The water tunnel experimental results showed that fluidelastic coupling between cylinders in water-flow has little effect on the critical flow velocity for fluidelastic instability, whereas the wind tunnel experimental results demonstrated that fluidelastic coupling between cylinders in airflow has a significant effect on the critical flow velocity. Therefore, for the cases with low mass ratio parameter the negative fluid damping mechanism dominated the fluidelastic instability of the array; however, for cases with high mass ratio, fluidelastic instability of the array was controlled by fluid stiffness effects. / An in-line square array with P/d = l.5 was also tested in the wind tunnel, with cylinders with high and low levels of mechanical damping. The experimental results showed that fluidelastic coupling between cylinders with low mechanical damping has a more significant effect on the critical flow velocity for fluidelastic instability than with high mechanical damping in airflow (with high mass ratio, $m/pd sp2$ = 860); hence, fluid stiffness-controlled mechanism becomes more important for fluidelastic instability of the array with low mechanical damping in airflow. Next, an in-line square array with P/d = 3.0 was tested in the wind tunnel. The results showed that one flexible cylinder becomes unstable when positioned in row 2 of the array; however, it does not become unstable when positioned in rows 3 or 4. This suggests that P/d has a large effect on fluidelastic instability behaviour of in-line square arrays. / Finally, a new constrained-mode approach, with a one-cylinder-kernel, has been developed for the instability analysis of both in-line and staggered arrays. The approach was developed to reduce the computational effort when a fully flexible cylinder array has to be analyzed, in order to take into account fluidelastic coupling; between cylinders.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.28437 |
| Date | January 1994 |
| Creators | Cheng, Boqian |
| 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: 001425279, proquestno: NN00086, Theses scanned by UMI/ProQuest. |
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