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Experimental investigation of low mo...

Gedikli, Ersegun Deniz.

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Experimental investigation of low mode number cylinders subjected to vortex-induced vibrations.

紀錄類型:	書目-電子資源 : Monograph/item
正題名/作者:	Experimental investigation of low mode number cylinders subjected to vortex-induced vibrations./
作者:	Gedikli, Ersegun Deniz.
面頁冊數:	150 p.
附註:	Source: Masters Abstracts International, Volume: 53-04.
Contained By:	Masters Abstracts International53-04(E).
標題:	Ocean engineering. -
電子資源:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=1563158
ISBN:	9781321113136

Experimental investigation of low mode number cylinders subjected to vortex-induced vibrations.
Gedikli, Ersegun Deniz.

Experimental investigation of low mode number cylinders subjected to vortex-induced vibrations. - 150 p.

Source: Masters Abstracts International, Volume: 53-04.

Thesis (M.S.)--University of Rhode Island, 2014.

This item is not available from ProQuest Dissertations & Theses.

The excitation of three low-mode number, flexible cylinders in uniform-flow is investigated to determine effects of structural mode shape on vortex-induced vibrations. Experiments are performed in a re-circulating flow channel and in a small flow visualization tank using object tracking and digital particle image velocimetry (DPIV) to measure the excitation of the cylinder, to estimate forces acting on the structure, and to observe the wake of the structure under the observed body motions. Previous research has focused on understanding the effect of in-line to cross-flow natural frequency ratio on the excitation of the structure in an attempt to model the excitation of multiple structural modes on long, flexible bodies. The current research investigates the impact of structural mode shape on this relationship by holding the in-line to cross-flow natural frequency constant and attempting to excite a specific structural mode shape. Understanding the effects of mode excitation will improve the ability to predict fatigue life in structures which may exhibit combined irregular and regular oscillations by understanding how mode shape affects the vibrating response. In this series of experiments, three cylinders are tested. The in-line to cross-flow natural frequency is kept constant with a ratio of 2:1, while the modes associated with these frequencies are varied: first mode inline to first mode cross-flow, second mode in-line to first mode cross-flow, and third mode in-line to first mode cross-flow.

ISBN: 9781321113136Subjects--Topical Terms:

660731
Ocean engineering.

Experimental investigation of low mode number cylinders subjected to vortex-induced vibrations.
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100 1 $a Gedikli, Ersegun Deniz. $3 3175740
245 1 0 $a Experimental investigation of low mode number cylinders subjected to vortex-induced vibrations.
300 $a 150 p.
500 $a Source: Masters Abstracts International, Volume: 53-04.
500 $a Adviser: Jason M. Dahl.
502 $a Thesis (M.S.)--University of Rhode Island, 2014.
506 $a This item is not available from ProQuest Dissertations & Theses.
506 $a This item must not be sold to any third party vendors.
520 $a The excitation of three low-mode number, flexible cylinders in uniform-flow is investigated to determine effects of structural mode shape on vortex-induced vibrations. Experiments are performed in a re-circulating flow channel and in a small flow visualization tank using object tracking and digital particle image velocimetry (DPIV) to measure the excitation of the cylinder, to estimate forces acting on the structure, and to observe the wake of the structure under the observed body motions. Previous research has focused on understanding the effect of in-line to cross-flow natural frequency ratio on the excitation of the structure in an attempt to model the excitation of multiple structural modes on long, flexible bodies. The current research investigates the impact of structural mode shape on this relationship by holding the in-line to cross-flow natural frequency constant and attempting to excite a specific structural mode shape. Understanding the effects of mode excitation will improve the ability to predict fatigue life in structures which may exhibit combined irregular and regular oscillations by understanding how mode shape affects the vibrating response. In this series of experiments, three cylinders are tested. The in-line to cross-flow natural frequency is kept constant with a ratio of 2:1, while the modes associated with these frequencies are varied: first mode inline to first mode cross-flow, second mode in-line to first mode cross-flow, and third mode in-line to first mode cross-flow.
520 $a It is found that it is difficult to isolate the effect of mode shape on the vibration of the structure as the cylinder can easily be excited with different combinations of modes. It is shown that for the low-mode number beams tested, there are three primary responses possible for the cylinder when trying to excite the first mode in the cross-flow direction and first mode in the in-line direction (cylinder 1), the first mode in the cross-flow direction and the second mode in the in-line direction (cylinder 2); and the first mode in the cross-flow direction and third mode in the in-line direction (cylinder 3).
520 $a Cylinder 1 response consists of an expected excitation of the first mode cross-flow with an excitation of the first mode frequency in in-line direction. Regular and periodic cylinder oscillations obtained along the length of the cylinder. Cylinder 2 response consists of an expected excitation of the first mode cross-flow with an excitation of the second mode frequency in in-line direction; however, the structural shape resembles the first mode shape. This response is attributed to the structural mode being an insufficient description of the phenomenon as the wake must be included as part of the mode shape. This response is characteristic of a figure eight response of the cylinder. In cylinder 3 experiments, two different responses as crescent and figure eight patterns were obtained. In this case, higher flow speeds could not be reached so third mode shape in the in-line direction could not be obtained.
520 $a The wake is observed using DPIV on a rigid cylinder with forced motions equivalent to the flexible body. A case of mode switching is also observed where the even in-line mode exhibits an excitation at twice the cross-flow frequency; however, the spatial mode shape in-line appears similar to the first structural mode shape. It is hypothesized that this situation is possible due to variation in the effective added mass along the length of the cylinder. Odd mode shapes in both in-line and cross-flow directions show similar motions to those observed for rigid cylinders.
590 $a School code: 0186.
650 4 $a Ocean engineering. $3 660731
650 4 $a Mechanical engineering. $3 649730
650 4 $a Naval engineering. $3 3173824
690 $a 0547
690 $a 0548
690 $a 0468
710 2 $a University of Rhode Island. $b Ocean Engineering. $3 3175737
773 0 $t Masters Abstracts International $g 53-04(E).
790 $a 0186
791 $a M.S.
792 $a 2014
793 $a English
856 4 0 $u http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=1563158