Stochastic modelling of cross-flow vortex-induced vibrations

Abstract Helical strakes can suppress vortex-induced vibrations (VIVs) in pipelines spans and risers. Pure in-line (IL) VIV is more of a concern for pipelines than for risers. To make it possible to assess the effectiveness of partial strake coverage for this case, an important gap in the hydrodynamic data for strakes is filled by the reported IL forced-vibration tests. Therein, a strake-covered rigid cylinder undergoes harmonic purely IL motion while subject to a uniform “flow” created by towing the test rig along SINTEF Ocean's towing tank. These tests cover a range of frequencies, and amplitudes of the harmonic motion to generate added-mass and excitation functions are derived from the in-phase and 90 deg out-of-phase components of the hydrodynamic force on the pipe, respectively. Using these excitation- and added-mass functions in VIVANA together with those from experiments on bare pipe by Aronsen (2007 “An Experimental Investigation of In-Line and Combined In-Line and Cross-Flow Vortex Induced Vibrations,” Ph.D. thesis, Norwegian University of Science and Technology, Trondheim, Norway.), the IL VIV response of partially strake-covered pipeline spans is calculated. It is found that as little as 10% strake coverage at the optimal location effectively suppresses pure IL VIV.

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Improved In-Line Vortex-Induced Vibrations Prediction for Combined In-Line and Cross-Flow Vortex-Induced Vibrations Responses

Journal of Offshore Mechanics and Arctic Engineering ◽

10.1115/1.4038350 ◽

2017 ◽

Vol 140 (3) ◽

Cited By ~ 1

Author(s):

Decao Yin ◽

Elizabeth Passano ◽

Carl M. Larsen

Keyword(s):

Cross Flow ◽

Hydrodynamic Coefficients ◽

Marine Structures ◽

Flexible Pipe ◽

Flexible Beams ◽

Forced Motion ◽

Pipe Model ◽

Vortex Induced Vibrations ◽

Flow Vortex ◽

Semi Empirical

Slender marine structures are subjected to ocean currents, which can cause vortex-induced vibrations (VIV). Accumulated damage due to VIV can shorten the fatigue life of marine structures, so it needs to be considered in the design and operation phase. Semi-empirical VIV prediction tools are based on hydrodynamic coefficients. The hydrodynamic coefficients can either be calculated from experiments on flexible beams by using inverse analysis or theoretical methods, or obtained from forced motion experiments on a circular cylinder. Most of the forced motion experiments apply harmonic motions in either in-line (IL) or crossflow (CF) direction. Combined IL and CF forced motion experiments are also reported. However, measured motions from flexible pipe VIV tests contain higher order harmonic components, which have not yet been extensively studied. This paper presents results from conventional forced motion VIV experiments, but using measured motions taken from a flexible pipe undergoing VIV. The IL excitation coefficients were used by semi-empirical VIV prediction software vivana to perform combined IL and CF VIV calculation. The key IL results are compared with Norwegian Deepwater Programme (NDP) flexible pipe model test results. By using present IL excitation coefficients, the prediction of IL responses for combined IL and CF VIV responses is improved.

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Phasing mechanisms between the in-line and cross-flow vortex-induced vibrations of a long tensioned beam in shear flow

Computers & Structures ◽

10.1016/j.compstruc.2013.01.002 ◽

2013 ◽

Vol 122 ◽

pp. 155-163 ◽

Cited By ~ 13

Author(s):

Rémi Bourguet ◽

George Em Karniadakis ◽

Michael S. Triantafyllou

Keyword(s):

Shear Flow ◽

Cross Flow ◽

Vortex Induced Vibrations ◽

Flow Vortex

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Interaction of In-Line and Cross-Flow Vortex Induced Vibrations in Risers

21st International Conference on Offshore Mechanics and Arctic Engineering, Volume 1 ◽

10.1115/omae2002-28303 ◽

2002 ◽

Cited By ~ 1

Author(s):

Erik Asp Hansen ◽

Mads Bryndum ◽

Stefan Mayer

Keyword(s):

Cross Flow ◽

Recent Model ◽

Experimental Investigations ◽

Numerical Tests ◽

Vortex Induced Vibrations ◽

Model Set ◽

Line Cross ◽

Set Up ◽

The Individual ◽

Flow Vortex

VIV in pipeline and risers has been studied through numerous experimental investigations using simplified model set-up, consisting of spring mounted rigid cylinders. Models have been constructed to allow in-line, cross-flow, or both in-line and cross-flow motions. Comparison of the model results shows overall agreement, although distinct differences exist between the individual model test series. Different explanation models have been established to try to improve the consistency, however, seldom definitive conclusions have been reached. The present paper presents the use of CFD to document the importance of the interaction of in-line and cross-flow motions on VIV response. 2D numerical tests have been performed using NS3 (DHI-CFD code) for a model undergoing in-line, cross-flow, combined in-line and cross-flow, and cross-flow in combination with forced in-line motions. The paper compares the results with some recent model tests and quantifies the significance of interaction.

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