Effects of Strake Coverage and Marine Growth on Flexible Cylinder Vortex-Induced Vibrations1

Resvanis, Themistocles L.; Rao, Zhibiao; Vandiver, J. Kim

doi:10.1115/1.4033821

Cited by 7 publications

(2 citation statements)

References 10 publications

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“…The properties of the riser model and the flow conditions are listed in Table 1. The physical properties are similar to those of a model that has been tested at Marintek in 2011, and described in [Resvanis et al, 2016] and [Rao et al, 2012]. In this numerical study the damping ratio in the power out region is varied systematically from 1.5% ~ 20% so as to illustrate that the response is insensitive to these values as long as infinite system behavior is observed.…”

Section: Numerical Examplementioning

confidence: 64%

Does More Tension Reduce VIV?

Vandiver

2017

Volume 5B: Pipelines, Risers, and Subsea Systems

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In this paper it is shown that for very long risers in sheared flow there is a surprising outcome — the VIV response amplitude in the power-in region does not depend at all on the amount of damping in the power out region, as long as it is sufficient to prevent waves from reflecting at the boundary and returning to the power-in region. In these cases, the response in the power-in region depends on the wave radiation damping and not on the damping in the power-out regions. Tension plays a major role in the determining the radiation damping and in some cases, but not all, pulling harder will indeed reduce response in the power-in region. Numerical simulations are presented in which a finite element model of a long riser is used to compute the VIV response in a sheared flow for which the power-in region is at one end of the riser. The radiated waves are shown to diminish with distance traveled as expected. When ζoutnout, the product of the number of wavelengths to reach the far termination and the damping ratio in the power-out region is greater than 0.18, it is shown that no significant vibration energy returns to the power-in region and the response in the power-in region is independent of the damping in the power-out region. The numerical simulation is used to illustrate the effect of changing tension on the radiation damping and therefore on the VIV response. The VIV response prediction program SHEAR7 is used to evaluate the effect of increasing tension on a realistic deepwater drilling riser in 3000 m water depth. A 20% increase in tension leads to a 12% reduction in fatigue damage rate.

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Section: Numerical Examplementioning

confidence: 64%

Does More Tension Reduce VIV?

Vandiver

2017

Volume 5B: Pipelines, Risers, and Subsea Systems

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“…Passive flow control does not require external supply of energy to work but relies on modifications of the shape or some other characteristic of the exterior surface of the body interacting with fluid flow. Helical strakes are often wrapped around long flexible pipelines that bring oil from the sea bottom so as to suppress unwanted flow-induced vibrations [7][8][9]. As an alternative to passively control the flow around a cylindrical structure, its surface can be fully or partially covered with hydrophobic or hairy-like microfiber coatings [10][11][12], or the geometry of the cylinder exterior be modified to have mild disturbances along its span [13,14].…”

Section: Flow Control Definitions and Preliminary Remarksmentioning

confidence: 99%

Active Control of Bluff-Body Flows Using Plasma Actuators

Konstantinidis

2019

Actuators

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Actuators play an important role in modern active flow control technology. Dielectric barrier discharge plasma can be used to induce localized velocity perturbations in air, so as to accomplish modifications to the global flow field. This paper presents a selective review of applications from the published literature with emphasis on interactions between plasma-induced perturbations and original unsteady fields of bluff-body flows. First, dielectric barrier discharge (DBD)-plasma actuator characteristics, and the local disturbance fields these actuators induce into the exterior flow, are described. Then, instabilities found in separated flows around bluff bodies that controlled actuation should target at are briefly presented. Key parameters for effective control are introduced using the nominally two-dimensional flow around a circular cylinder as a paradigm. The effects of the actuator configuration and location, amplitude and frequency of excitation, input waveform, as well as the phase difference between individual actuators are illustrated through examples classified based on symmetry properties. In general, symmetric excitation at frequencies higher than approximately five times the uncontrolled frequency of vortex shedding acts destructively on regular vortex shedding and can be safely employed for reducing the mean drag and lift fluctuations. Antisymmetric and symmetric excitation at low frequencies of the order of the natural frequency can amplify the wake instability and increase the mean and fluctuating aerodynamic forces, respectively, due to vortex locking-on to the excitation frequency or its subharmonics. Results from several studies show that the geometry and arrangement of the electrodes is of utmost significance. Power consumption is typically very low, but the electromechanical efficiency can be optimized by input waveform modulation.

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Revealing the effects of damping on the flow-induced vibration of flexible cylinders

Vandiver

Rao

2018

Journal of Sound and Vibration

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Effects of Strake Coverage and Marine Growth on Flexible Cylinder Vortex-Induced Vibrations1

Cited by 7 publications

References 10 publications

Does More Tension Reduce VIV?

Does More Tension Reduce VIV?

Active Control of Bluff-Body Flows Using Plasma Actuators

Revealing the effects of damping on the flow-induced vibration of flexible cylinders

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