Multi-mode interactions in vortex-induced vibrations of flexible curved/straight structures with geometric nonlinearities

In search for new gas and oil fields, the trend in offshore development points towards deeper waters, harsher environment, increased use of subsea installations and use of pipelines to transport the hydrocarbons to processing facilities onshore or in shallower waters. This also implies installation of pipelines at very uneven seabed causing a high number of spans that can be difficult and very costly to intervene. Conventional free span design according to the DNV Recommended Practice DNV-RP-F105 (2002) allows for vortex induced vibrations (VIV) as long as the integrity of the pipeline is within acceptable limits. However, the 2002 issue of the design code mainly covers short and moderate spans. As the knowledge about very long and/or multiple spans, where several vibration modes may be activated, has been limited, such cases have been treated in an assumed conservative way. This paper discusses the technical advancements in free span design in general and with respect to both long free spans and multi-spanning sections where several vibration modes may be activated simultaneously in particular. These advancements form the basis for the updated DNV-RP-F105 (2006). Changes from the former 2002 version are illustrated by an examples and the technical background is discussed.

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Multi-mode interactions in nonlinear circuits: validity limits of linear approximation

2005 18th International Conference on Applied Electromagnetics and Communications ◽

10.1109/icecom.2005.205047 ◽

2005 ◽

Author(s):

V.B. Ryabov ◽

T. Sugawara

Keyword(s):

Linear Approximation ◽

Nonlinear Circuits ◽

Mode Interactions ◽

Multi Mode

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Numerical and Experimental Comparisons of Vortex-Induced Vibrations of Marine Risers in Uniform/Sheared Currents

29th International Conference on Ocean, Offshore and Arctic Engineering: Volume 6 ◽

10.1115/omae2010-20192 ◽

2010 ◽

Author(s):

Narakorn Srinil ◽

Patrick O’Brien ◽

Marian Wiercigroch

Keyword(s):

Nonlinear Models ◽

Cross Flow ◽

Experimental Results ◽

Beam Model ◽

Geometric Nonlinearities ◽

Marine Risers ◽

Wake Oscillator ◽

Damage Indices ◽

Multi Mode ◽

Experimental Comparisons

This paper presents a general theoretical reduced-order model capable of evaluating the multi-mode nonlinear dynamics of marine risers subject to uniform and sheared currents. The main objectives are to predict the vortex-induced vibration responses and parametrically compare between numerical and experimental results. The emphasis is placed on the analysis of cross-flow vibrations due to unsteady lift forces. The nonlinear equations governing riser axial/transversal motions are derived based on a top-tensioned beam model with typical pinned-pinned boundary conditions. The riser geometric nonlinearities owing to possible large dynamic displacements and multi-mode interactions are accounted for. To approximate the space-time varying lift force, the empirical hydrodynamic model, based on a nonlinear van der Pol wake oscillator with a distributed diffusive term, is used. A low-dimensional dynamic model and computationally-robust time-domain tool are then developed to evaluate the multi-mode fluid-riser interactions. These are very useful in dealing with large parametric studies involving varying system parameters. Comparisons of numerical and experimental results are performed by estimating riser response amplitudes and fatigue damage indices. Both linear and nonlinear risers are considered in the present numerical model whereas only linear riser has been considered by a referenced literature in the reconstruction of experimental displacements through measured strains. It is found that riser geometric nonlinearities play a significant role in both numerical simulations and comparisons with experiment post-processed results. In some cases, quantitative/qualitative discrepancies in riser response predictions are remarkable with linear vs. nonlinear models. These may be recognized as one of the factors why recent numerical and experimental comparisons in literature have been unsuccessful.

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On the force distribution along the axis of a flexible circular cylinder undergoing multi-mode vortex-induced vibrations

Journal of Fluids and Structures ◽

10.1016/j.jfluidstructs.2006.04.014 ◽

2006 ◽

Vol 22 (6-7) ◽

pp. 897-903 ◽

Cited By ~ 60

Author(s):

F.J. Huera Huarte ◽

P.W. Bearman ◽

J.R. Chaplin

Keyword(s):

Circular Cylinder ◽

Force Distribution ◽

Vortex Induced Vibrations ◽

Multi Mode

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Multi-mode interactions in an FEL oscillator

Nuclear Instruments and Methods in Physics Research Section A Accelerators Spectrometers Detectors and Associated Equipment ◽

10.1016/s0168-9002(00)00121-2 ◽

2000 ◽

Vol 445 (1-3) ◽

pp. 101-104 ◽

Cited By ~ 1

Author(s):

Zhi-Wei Dong ◽

Jiro Kitagaki ◽

Kai Masuda ◽

Tetsuo Yamazaki ◽

Kiyoshi Yoshikawa

Keyword(s):

Mode Interactions ◽

Multi Mode

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Multi-mode light microscopy of microtubule assembly dynamics and chromosome movement in vivo and In vitro

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100166117 ◽

1996 ◽

Vol 54 ◽

pp. 730-731

Author(s):

E. D. Salmon ◽

J. C. Waters ◽

C. Waterman-Storer

Keyword(s):

Imaging System ◽

Ccd Camera ◽

Transmitted Light ◽

Microtubule Assembly ◽

Live Cells ◽

Optical Efficiency ◽

Multiple Band ◽

Multi Mode

We have developed a multi-mode digital imaging system which acquires images with a cooled CCD camera (Figure 1). A multiple band pass dichromatic mirror and robotically controlled filter wheels provide wavelength selection for epi-fluorescence. Shutters select illumination either by epi-fluorescence or by transmitted light for phase contrast or DIC. Many of our experiments involve investigations of spindle assembly dynamics and chromosome movements in live cells or unfixed reconstituted preparations in vitro in which photodamage and phototoxicity are major concerns. As a consequence, a major factor in the design was optical efficiency: achieving the highest image quality with the least number of illumination photons. This principle applies to both epi-fluorescence and transmitted light imaging modes. In living cells and extracts, microtubules are visualized using X-rhodamine labeled tubulin. Photoactivation of C2CF-fluorescein labeled tubulin is used to locally mark microtubules in studies of microtubule dynamics and translocation. Chromosomes are labeled with DAPI or Hoechst DNA intercalating dyes.

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