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Vortex-Induced Vibration and Forced Oscillation Motion of a Circular Cylinder Fitted with a Single Spanwise Tripwire.

Record Type:	Electronic resources : Monograph/item
Title/Author:	Vortex-Induced Vibration and Forced Oscillation Motion of a Circular Cylinder Fitted with a Single Spanwise Tripwire./
Author:	Vaziri, Ehsan.
Published:	Ann Arbor : ProQuest Dissertations & Theses, : 2021,
Description:	163 p.
Notes:	Source: Dissertations Abstracts International, Volume: 83-01, Section: B.
Contained By:	Dissertations Abstracts International83-01B.
Subject:	Aerospace engineering. -
Online resource:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=28262149
ISBN:	9798522942588

Vortex-Induced Vibration and Forced Oscillation Motion of a Circular Cylinder Fitted with a Single Spanwise Tripwire.
Vaziri, Ehsan.

Vortex-Induced Vibration and Forced Oscillation Motion of a Circular Cylinder Fitted with a Single Spanwise Tripwire. - Ann Arbor : ProQuest Dissertations & Theses, 2021 - 163 p.

Source: Dissertations Abstracts International, Volume: 83-01, Section: B.

Thesis (Ph.D.)--University of Toronto (Canada), 2021.

This item must not be sold to any third party vendors.

This experimental study consisted of two main parts. The first part investigated the control induced by a spanwise tripwire on a circular cylinder undergoing one-degree-of-freedom vortex-induced vibration (VIV). The cylinder vibrates in the cross-stream direction as a result of the fluid forcing in a recirculating water tunnel. Changing mass and damping ratios in the test rig allowed the investigation at different VIV response branches. The tripwire diameter was 6.25% of the cylinder diameter. Experimental research was conducted by attaching the large-scale tripwire along the span of the cylinder at various angular positions ranging from 0° to 180° (with respect to the most upstream point of the cylinder). Along with measuring the trajectory of the cylinder motion, the instantaneous velocity field in the near wake of the cylinder was obtained simultaneously at a fixed Reynolds number of 10,000 (based on the cylinder diameter) using a Particle Image Velocimetry (PIV) system. Various vortex-formation modes induced by the tripwire were observed. It was shown that the oscillation pattern, frequency, and amplitude of the cylinder can be altered significantly depending on the angular position of the tripwire and the VIV response branch. For specific tripwire positions, increases of up to 52 times and decreases of up to 98% were identified in the oscillation amplitude of the tripped cylinder compared to the amplitude of the clean cylinder.The second part of the study investigated the effects of the tripwire on the flow structure behind a circular cylinder forced to oscillate harmonically at prescribed amplitudes and frequencies in the cross-stream direction. Oscillation amplitudes are 0.05, 0.3 and 0.6 times the cylinder diameter, and oscillation frequencies are 0.61, 0.8, and 1 times the vortex shedding frequency of the stationary clean cylinder counterpart. For a fixed oscillation amplitude and frequency, the tripwire can either induce intermittent switching between various vortex shedding modes or cause a wake mode to be dominant during the entire observed oscillation motion by altering the vortex shedding mechanism. The wake of the tripped cylinder undergoing the lowest amplitude forced oscillation motion showed resemblance to the wake of the stationary tripped cylinder.

ISBN: 9798522942588Subjects--Topical Terms:

1002622
Aerospace engineering.
Subjects--Index Terms:

Cylindrical structure

Vortex-Induced Vibration and Forced Oscillation Motion of a Circular Cylinder Fitted with a Single Spanwise Tripwire.
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245 1 0 $a Vortex-Induced Vibration and Forced Oscillation Motion of a Circular Cylinder Fitted with a Single Spanwise Tripwire.
260 1 $a Ann Arbor : $b ProQuest Dissertations & Theses, $c 2021
300 $a 163 p.
500 $a Source: Dissertations Abstracts International, Volume: 83-01, Section: B.
500 $a Advisor: Ekmekci, Alis.
502 $a Thesis (Ph.D.)--University of Toronto (Canada), 2021.
506 $a This item must not be sold to any third party vendors.
520 $a This experimental study consisted of two main parts. The first part investigated the control induced by a spanwise tripwire on a circular cylinder undergoing one-degree-of-freedom vortex-induced vibration (VIV). The cylinder vibrates in the cross-stream direction as a result of the fluid forcing in a recirculating water tunnel. Changing mass and damping ratios in the test rig allowed the investigation at different VIV response branches. The tripwire diameter was 6.25% of the cylinder diameter. Experimental research was conducted by attaching the large-scale tripwire along the span of the cylinder at various angular positions ranging from 0° to 180° (with respect to the most upstream point of the cylinder). Along with measuring the trajectory of the cylinder motion, the instantaneous velocity field in the near wake of the cylinder was obtained simultaneously at a fixed Reynolds number of 10,000 (based on the cylinder diameter) using a Particle Image Velocimetry (PIV) system. Various vortex-formation modes induced by the tripwire were observed. It was shown that the oscillation pattern, frequency, and amplitude of the cylinder can be altered significantly depending on the angular position of the tripwire and the VIV response branch. For specific tripwire positions, increases of up to 52 times and decreases of up to 98% were identified in the oscillation amplitude of the tripped cylinder compared to the amplitude of the clean cylinder.The second part of the study investigated the effects of the tripwire on the flow structure behind a circular cylinder forced to oscillate harmonically at prescribed amplitudes and frequencies in the cross-stream direction. Oscillation amplitudes are 0.05, 0.3 and 0.6 times the cylinder diameter, and oscillation frequencies are 0.61, 0.8, and 1 times the vortex shedding frequency of the stationary clean cylinder counterpart. For a fixed oscillation amplitude and frequency, the tripwire can either induce intermittent switching between various vortex shedding modes or cause a wake mode to be dominant during the entire observed oscillation motion by altering the vortex shedding mechanism. The wake of the tripped cylinder undergoing the lowest amplitude forced oscillation motion showed resemblance to the wake of the stationary tripped cylinder.
590 $a School code: 0779.
650 4 $a Aerospace engineering. $3 1002622
650 4 $a Fluid mechanics. $3 528155
650 4 $a Mechanical engineering. $3 649730
650 4 $a Vortices. $3 3681507
650 4 $a Flow velocity. $3 3564851
650 4 $a Fourier transforms. $3 3545926
650 4 $a Reynolds number. $3 3681436
650 4 $a Experiments. $3 525909
653 $a Cylindrical structure
653 $a Flow-structure interactions
653 $a Forced oscillation motion
653 $a Tripwire
653 $a Vortex-induced vibration
690 $a 0538
690 $a 0548
690 $a 0204
710 2 $a University of Toronto (Canada). $b Aerospace Science and Engineering. $3 2105951
773 0 $t Dissertations Abstracts International $g 83-01B.
790 $a 0779
791 $a Ph.D.
792 $a 2021
793 $a English
856 4 0 $u http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=28262149