Chaotic response is a generic feature of vortex-induced vibrations of flexible risers

Modarres‐Sadeghi, Yahya; Chasparis, Filippos; Triantafyllou, Michael S.; Tognarelli, Michael A.; Beynet, Pierre

doi:10.1016/j.jsv.2010.12.007

Cited by 70 publications

(37 citation statements)

References 23 publications

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“…The amplitudes are severely reduced in time intervals where there is no clear dominating frequency. For other time periods the response is steady-state and amplitudes are high, all in agreement with findings by Modarres-Sadeghi et al (2011). To exemplify, the low current case (figure 17) shows a shift of dominating frequency at t ≈ 30s, at the same time as the strain amplitude experiences a sudden and short drop.…”

Section: Detailed Observationssupporting

confidence: 84%

“…Modarres-Sadeghi et al (2011) utilized data from experiments by the Norwegian Deepwater Programme (NDP) of long slender risers (Braaten and Lie, 2005), separating the response into three branches. The VIV could be entirely quasi-periodic with statistically stationary properties, in the sense that one frequency and mode occupied the entire structure for the whole time window, typically in combination with higher harmonics.…”

Section: Introductionmentioning

confidence: 99%

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Stochastic modelling of cross-flow vortex-induced vibrations

et al. 2017

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Semi-empirical models are commonly used to predict vortex-induced vibrations (VIV). Empirical parameters are often based on forced harmonic motion tests of short rigid cylinders in one degree of freedom, which is a significant simplification of the three dimensional VIV experienced by flexible cylinders. Still, the models may provide satisfactory estimates of the response of slender marine structures exposed to current. At least in terms of root mean square (r.m.s.) of displacements and strains, dominating frequency and dominating mode. However, VIV of long slender beams, especially in sheared current, show large response variability in time and space, which appears to be of a random nature. Semi-empirical models that predict steady-state VIV are hence unable to reflect the non-stationary response observed in experiments, even though the time and space averaged result might be well represented.In this work, a previously published semi-empirical time domain model for cross-flow vortex-induced vibrations is modified to describe the stochastic nature of the response of long slender beams subjected to stationary current. The mean non-dimensional frequency of the synchronization model (previously constant) is taken to be a simplified Gaussian process, where standard deviation and spectral frequencies are input. The stochastic synchronization model allows the response to jump between different eigenfrequencies and corresponding modes, and still predict mean and r.m.s. values close to the deterministic model. Its performance is verified through simulation of an experiment with a long riser in sheared flow. The response sensitivity of standard deviation and spectral frequencies is investigated. It indicates that for a proper choice of empirical coefficients, the chaotic response of the riser can be quite realistically simulated in terms of frequency variation and, to some extent, amplitude modulation.

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Section: Detailed Observationssupporting

confidence: 84%

Section: Introductionmentioning

confidence: 99%

Stochastic modelling of cross-flow vortex-induced vibrations

et al. 2017

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“…The fundamentals of VIV have been well documented for a cylinder whose axis in quiescient fluid is perpendicular to the oncoming flow (normal incidence case), the body being either rigid and elastically-mounted (King et al 1973;Bearman 1984Bearman , 2011Naudascher 1987;Mittal & Tezduyar 1992;Hover et al 1998;Okajima et al 2002;Sarpkaya 2004;Williamson & Govardhan 2004;Klamo et al 2006;Leontini et al 2006;Benaroya & Gabbai 2008;Lucor & Triantafyllou 2008;Dahl et al 2010;Navrose & Mittal 2013;Cagney & Balabani 2014;Konstantinidis 2014) or flexible (Trim et al 2005;Chaplin et al 2005;Lie & Kaasen 2006;Lucor et al 2006;Huera-Huarte & Bearman 2009, 2014; Vandiver et al 2009;Modarres-Sadeghi et al 2011;Bourguet et al 2011aBourguet et al ,b, 2012Bourguet et al , 2013a. VIV naturally appear both in the cross-flow direction and in the in-line direction, i.e.…”

Section: Introductionmentioning

confidence: 99%

The onset of vortex-induced vibrations of a flexible cylinder at large inclination angle

Bourguet

Triantafyllou

2016

J. Fluid Mech.

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The onset of the vortex-induced vibration (VIV) regime of a flexible cylinder inclined at 80 • within a uniform current is studied by means of direct numerical simulations, at Reynolds number 500, based on the body diameter and inflow velocity magnitude. A range of values of the reduced velocity, defined as the inverse of the fundamental natural frequency, is examined in order to capture the emergence of the body responses and explore the concomitant reorganization of the flow and fluid forcing. Additional simulations at normal incidence confirm that the independence principle, which states that the system behavior is determined by the normal inflow component, does not apply at such large inclination angle. Contrary to the normal incidence case, the free vibrations of the inclined cylinder arise far from the Strouhal frequency, i.e. the vortex shedding frequency downstream of a fixed rigid cylinder. The trace of the stationary body wake is found to persist beyond the vibration onset: the flow may still exhibit an oblique component that relates to the slanted vortex shedding pattern observed in the absence of vibration. This flow component which occurs close to the Strouhal frequency, at a high and incommensurable frequency compared to the vibration frequency, is referred to as Strouhal component; it induces a high-frequency component in fluid forcing. The vibration onset is accompanied by the appearance of novel, low-frequency components of the flow and fluid forcing, which are synchronized with body motion. This second dominant flow component, referred to as lock-in component, is characterized by a parallel spatial pattern. The Strouhal and lock-in components of the flow coexist over a range of reduced velocities, with variable contributions, which results in a variety of mixed wake patterns. The transition from oblique to parallel vortex shedding, that occurs during the amplification of the structural responses, is driven by the opposite trends of these two component contributions: the decrease of the Strouhal component magnitude, associated with the progressive disappearance of the high-frequency force component, and simultaneously, the increase of the lock-in component magnitude, which dominates once the fully-developed VIV regime is reached and the flow dynamics is entirely governed by wake-body synchronization.

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“…Chaotic FSI gives rise to many practical problems such as snap loading (Connell & Yue 2007), buckling of wings in aircraft manoeuvres (Sipcic 1990) and ship roll and capsize (Spyrou & Thompson 2000). The broad frequency response of chaotic mechanical systems is also important, with its impact on the fatigue life of structures (Modarres-Sadeghi et al 2011;Dahl et al 2007), and its ability to maximize response of sensors and energy extraction devices over a broad range of excitation frequencies (Arrieta et al 2010;Townsend & Shenoi 2013).…”

Section: Introductionmentioning

confidence: 99%

“…While the fluid supplies infinitely many degrees of freedom and nonlinear forcing even at low Reynolds number, previous example systems depend strongly on continuously deformable or multilinkage structures or on turbulent flow. Indeed, the onset of chaotic motions in long flexible risers is attributed to the interaction of many structural modes in the inline and crossflow directions along the span (Modarres-Sadeghi et al 2011). And flapping membranes with excessive stiffness or reduced mass-ratio exhibit only simple period-1 oscillations up to Re = 5000 (Connell & Yue 2007).…”

Section: Introductionmentioning

confidence: 99%

Chaotic rotation of a towed elliptical cylinder

Weymouth

2014

J. Fluid Mech.

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In this paper I consider the self-excited rotation of an elliptical cylinder towed in a viscous fluid as a canonical model of nonlinear fluid structure interactions with possible applications in the design of sensors and energy extraction devices. First, the self-excited ellipse system is shown to be analogous to the forced bistable oscillators studied in classic chaos theory. A single variable, the distance between the pivot and the centroid, governs the system bifurcation into bi-stability. Next, fully coupled computational fluid dynamics simulations of the motion of the cylinder demonstrate limit cycle, period doubling, intermittently chaotic, and fully chaotic dynamics as the distance is further adjusted. The viscous wake behind the cylinder is presented for the limit cycle cases and new types of stable wakes are characterized for each. In contrast, a chaotic case demonstrates an independence of the wake and structural states. The rotational kinetic energy is quantified and correlated to the vortex shedding and the trajectory periodicity. Chaotic and high-period system responses are found to persist when structural damping is applied and for Reynolds numbers as low as 200.

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Chaotic response is a generic feature of vortex-induced vibrations of flexible risers

Cited by 70 publications

References 23 publications

Stochastic modelling of cross-flow vortex-induced vibrations

Stochastic modelling of cross-flow vortex-induced vibrations

The onset of vortex-induced vibrations of a flexible cylinder at large inclination angle

Chaotic rotation of a towed elliptical cylinder

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