Vortex-Induced Vibrations of Steel Catenary Risers and Steel Offloading Lines due to Platform Heave Motions

Chang, Stephen; Isherwood, Mike

doi:10.4043/15106-ms

Cited by 10 publications

(3 citation statements)

References 3 publications

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“…The semi-empirical frequency domain methods VIVA (Triantafyllou et al, 1999), SHEAR7 (Vandiver and Li, 2005) and VIVANA (Larsen et al, 2009) are more efficient, but can only predict VIV in stationary flows. As illustrated by Chang et al (2003), the wake-oscillator can be used to simulate VIV in time domain for unsteady flow situations, but no comparison with experiment was included in this study. Liao (2001) was able to predict VIV in unsteady flow based on a relationship between an equivalent reduced damping and the resulting vibration amplitude.…”

Section: Introductionmentioning

confidence: 99%

Time domain simulation of vortex-induced vibrations in stationary and oscillating flows

Thorsen

Sævik

Larsen

2016

Journal of Fluids and Structures

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This paper focuses on the further development of a previously published semi-empirical method for time domain simulation of vortex-induced vibrations (VIV). A new hydrodynamic damping formulation is given, and the necessary coefficients are found from experimental data. It is shown that the new model predicts the observed hydrodynamic damping in still water and for cross-flow oscillations in stationary incoming flow with high accuracy. Next, the excitation force model is optimized by simulating the VIV response of an elastic cylinder in a series of experiments with stationary flow. The optimization is performed by repeating the simulations until the best possible agreement with the experiments is found. The optimized model is then applied to simulate the cross-flow VIV of an elastic cylinder in oscillating flow, without introducing any changes to the hydrodynamic force modeling. By comparison with experiment, it is shown that the model predicts the frequency content, mode and amplitude of vibration with a high level of realism, and the amplitude modulations occurring at high Keulegan-Carpenter numbers are well captured. The model is also utilized to investigate the effect of increasing the maximum reduced velocity and the mass ratio of the elastic cylinder in oscillating flow. Simulations show that complex response patterns with multiple modes and frequencies appear when the maximum reduced velocity is increased. If, however, the mass ratio is increased by a factor of 5, a single mode dominates. This illustrates that, in oscillating flows, the mass ratio is important in determining the mode participation at high maximum reduced velocities.

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Section: Introductionmentioning

confidence: 99%

Time domain simulation of vortex-induced vibrations in stationary and oscillating flows

Thorsen

Sævik

Larsen

2016

Journal of Fluids and Structures

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“…However, no experimental validation was included in that work. This was also the case for a numerical study by Chang and Isherwood [4], where cross-flow VIV simulations of an SCR, vibrating due to vessel heave motion, was carried out. Here, two time domain prediction tools were compared, i.e.…”

Section: Introductionmentioning

confidence: 92%

Time domain simulation of riser VIV in current and irregular waves

et al. 2018

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A semi-empirical time domain force model for combined cross-flow and in-line vortex-induced vibrations (VIV) is proposed, based on a series of earlier publications. The new feature is a term which represents the effect of vortex shedding in the flow direction, referred to as the in-line vortex shedding load. The latter is added to Morison's equation and a cross-flow vortex shedding force. The fundamental idea of how to model the effect of vortex shedding is the same as in previous works. An algorithm for synchronization is applied between the vortex shedding loading terms themselves and the structural response, which excites vibrations for a pre-determined frequency interval. The originality of the present study is rather how the VIV-terms are integrated as part of Morison's equation, which is there to provide a description of inertia and drag forces. All the loading terms combined enables simultaneous simulation of VIV and other response phenomena, such as wave induced motion and static drag displacement.The performance of the time domain model is verified against measurements of a vertical riser subjected to two different external flow cases. The first one is simply steady uniform current whereas the second flow case combines the latter with irregular waves. To simulate the experiments, a linear finite element model of the riser is made, and the proposed hydrodynamic force model is applied to the translation degrees of freedom along the structure. It is to be noted that the same empirical coefficients are used to simulate both experiments. In uniform flow, the results are good. Dominating frequency and vibration amplitude agree well in both cross-flow and in-line directions. The simulated time series show more regular/less tendency of amplitude modulations than the experiments, but the overall agreement is still acceptable for engineering purposes. For the second flow case, where the riser was towed in irregular waves, the model provides a highly realistic representation of the riser motion. Both when the total response (containing wave and VIV frequencies) and the filtered signal (including only VIV frequencies) are analysed, the predictions follow the measurements closely. From before, the cross-flow part of the VIV model has been tested in oscillating flow and regular waves, and the performance of the former was experimentally proven. It is hence concluded that the proposed prediction tool is applicable to a variety of non-stationary flow conditions, implying that the synchronization model captures parts of the underlying physics, despite its simple form.

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“…Therefore, some researchers focus on time domain approach for CF-VIV prediction. Chang and Isherwood [7] developed a time domain VIV prediction code using wake-oscillator model and vortex tracking model. Srinil [8] simulated Tognarelli's laboratory test model [9] using wake-oscillator model by assuming the riser response frequency locked in the Strouhal frequency associated with the maximum current velocity.…”

Section: Introductionmentioning

confidence: 99%

A practical approach to predicting cross-flow and in-line VIV response for deepwater risers

Xue

Wang

Tang

2015

Applied Ocean Research

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Vortex-Induced Vibrations of Steel Catenary Risers and Steel Offloading Lines due to Platform Heave Motions

Cited by 10 publications

References 3 publications

Time domain simulation of vortex-induced vibrations in stationary and oscillating flows

Time domain simulation of vortex-induced vibrations in stationary and oscillating flows

Time domain simulation of riser VIV in current and irregular waves

A practical approach to predicting cross-flow and in-line VIV response for deepwater risers

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