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Research Papers: Technical Forum

Estimation of the Time Delay Associated With Damping Controlled Fluidelastic Instability in a Normal Triangular Tube Array

[+] Author and Article Information
John Mahon

e-mail: mahonjp@tcd.ie

Craig Meskell

e-mail: cmeskell@tcd.ie
Department of Mechanical Engineering,
Trinity College,
Dublin 2, Ireland

Contributed by the Pressure Vessel and Piping Division of ASME for publication in the JOURNAL OF PRESSURE VESSEL TECHNOLOGY. Manuscript received May 19, 2012; final manuscript received March 29, 2013; published online May 21, 2013. Assoc. Editor: Jong Chull Jo.

J. Pressure Vessel Technol 135(3), 030903 (May 21, 2013) (7 pages) Paper No: PVT-12-1060; doi: 10.1115/1.4024144 History: Received May 19, 2012; Revised March 29, 2013

Fluidelastic instability (FEI) produces large amplitude self-excited vibrations close to the natural frequency of the structure. For fluidelastic instability caused by the damping controlled mechanism, there is a time delay between tube motion and the resulting fluid forces but magnitude and physical cause of this is unclear. This study measures the time delay between tube motion and the resulting fluid forces in a normal triangular tube array with a pitch ratio of 1.32 subject to air cross-flow. The instrumented cylinder was forced to oscillate in the lift direction at three excitation frequencies for a range of flow velocities. Unsteady surface pressures were monitored with a sample frequency of 2 kHz at the mid plane of the instrumented cylinder. The instantaneous fluid forces were obtained by integrating the surface pressure data. A time delay between the tube motion and resulting fluid forces was obtained. The nondimensionalized time delay was of the same order of magnitude assumed in the semi-empirical quasi-steady model (i.e., τ2 = 0.29 d/U). Although, further work is required to provide a parameterized model of the time delay which can be embedded in a model of damping controlled fluidelastic forces, the data already provides some insight into the physical mechanism responsible.

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Figures

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Fig. 1

Test section schematic

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Fig. 3

Measurement chain—block diagram

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Fig. 4

Schematic of position angle

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Fig. 5

Uncorrected time delay against velocity at a tube excitation frequency of 8.6 Hz. Tube amplitudes; Δ, 1%; ○, 2%; □, 2.5%; and ⊲−3%

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Fig. 6

Uncorrected time delay at various tube excitation frequencies; Δ, 6.6 Hz; ○, 8.6 Hz; and □, 10.6 Hz

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Fig. 7

Nondimensional time delay (τ1) against reduced velocity at various tube excitation frequencies; Δ, 6.6 Hz; ○, 8.6 Hz; and □, 10.6 Hz

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Fig. 8

Nondimensional time delay (τ2) against Reynolds number at various tube excitation frequencies; Δ, 6.6 Hz; ○, 8.6 Hz; and □, 10.6 Hz

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Fig. 9

Time delay against velocity at various tube excitation frequencies; Δ, 6.6 Hz; ○, 8.6 Hz; ◊, 10.6 Hz. –, Price and Paidoussis model (μ = 0.29).

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Fig. 10

P/d = 1.32; Mean CP at various tube displacements, U = 7 m/s (Re = 7.82 × 104)

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Fig. 11

Normalized RMS pressure at an excitation frequency of 10.6 Hz against position angle

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Fig. 12

Time delay at an excitation frequency of 10.6 Hz for various position angles

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Fig. 13

Time delay over a range of position angles: ◊, U = 4 m/s; □, U = 7 m/s; and ○, U = 10 m/s

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