Proceedings of the Thirty-second (2022) International Ocean and Polar Engineering Conference
Shanghai, China, June 5–10, 2022
Copyright © 2022 by the International Society of Offshore and Polar Engineers (ISOPE)
ISBN 978-1-880653-81-4; ISSN 1098-6189

www.isope.org

Inferring optimal hydrodynamic databases for vortex induced cross flow vibration prediction of marine
risers using limited sensor measurements.

Andreas Mentzelopoulos a, José del Águila Ferrandis a, Dixia Fan a,b, Samuel Rudy a, Themistoklis Sapsis a, Michael S. Triantafyllou aa

Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, MA, USAb
School of Engineering, Westlake University, Hangzhou, Zhejiang, China

ABSTRACT

shedding and body motion takes place (Williamson et al., 2004, Wanget al., 2020). During “lock-in”, moderate response amplitudes occur,
typically self-limited to about one diameter. The vortex shedding
frequency can differ from the Strouhal frequency of a fixed cylinder
because, as work via flow visualization has revealed, the relative motion
between the vibrating cylinder and the shed vortices can significantly
alter the effective fluid added mass (Wang et al., 2021), resulting in avariable natural frequency as a function of stream velocity (Williamsonet al., 1996).

Accurate prediction of the structural response of flexible cylinder
vortex-induced vibrations (VIVs) relies heavily on the accuracy of theacquired hydrodynamic coefficient database. Due to a large number ofvariables, the construction of systematic hydrodynamic databases fromrigid cylinder forced vibration experiments can be time-consuming oreven intractable. A novel approach has been implemented in this paper
to improve the flexible cylinder VIV prediction by inferring the optimal
parametric hydrodynamic database using measurements along withthe structure; such a methodology has been demonstrated for uniform
straight (flexible) risers in uniform flow using displacement data. This
work extends the framework and applies it to the straight riser problem
using only limited strain measurements. The predicted amplitude andfrequency responses are compared with experimental results.

Through experimental (Hover et al., 2001, Raghavan et al., 2011, Xu etal., 2013) and numerical (Evangelinos et al., 2000, Wu et al., 2014, Wanget al., 2021) methods, studies revealed that significant variations of thefluid forces on an oscillating rigid cylinder could occur as a function of
the oncoming stream velocity and cylinder motions. These variations are
due to changes in the vortex shedding pattern. Therefore, experiments
were conducted where a rigid cylinder was forced a prescribed motion ina prescribed flow condition (Sarpkaya et al., 1978). In particular, studies
focused on the mean drag coefficient Cd , the lift coefficient in-phase withthe velocity Clv and the added mass coefficient in the CF direction Cmy asfunctions of the true reduced velocity Vr = fUd and non-dimensional CF

KEY WORDS: Vortex Induced Vibration; VIV; Marine Risers; Hydrodynamic Database; Optimization; Parametric Database.

INTRODUCTION
Vortex-Induced Vibrations (VIV) have been known to engineers formore than 400 years, first observed by Leonardo da Vinci as ”AeolianTones,” sounds created by vortex-induced pressure fluctuations as thewind passes around obstacles. Extensive studies on the subject havesince been conducted (Williamson et al., 2004, Williamson et al., 2008,Bearman et al., 2011, Wu et al., 2012, Wang et al., 2020) , in orderto mainly suppress VIV due to their destructive capabilities (Park etal., 2016, Bernitsas et al., 2008, Baek et al., 2009). VIV affect bluff
bodies in the presence of currents due to periodic shedding vortices
developed in the wake aft bodies. Those vortices lead to an alternatingpressure, and if the body is free to move, the pressure variations will
synchronize with body motion, creating consistent vibrations. If not
dealt with properly, VIV can cause extensive fatigue damage over a
prolonged period (Bernitsas et al., 2019). Given the bluff nature of many
modern offshore engineering equipment, such as cables, mooring lines,
and marine risers (Wu et al., 2017, Fan et al., 2017, Fan et al., 2019), a
thorough understanding of the underlying physics of VIV is essential incontrolling their effects be they fatigue damage to offshore equipment orenergy harnessed from flows (Bernitsas et al., 2008).

Aamplitude dy , where U is the prescribed fluid velocity; f the prescribedmotion frequency; Ay the prescribed motion amplitude; and d thecylinder model diameter (Gopalkrishnan et al., 1993, Sarpkaya et al.,
1995, Fan et al., 2019). The experiments showed that regions of positive
Clv , denoting net energy transferred from the fluid to structure over one
Amotion period, were located in a certain range of Vr and dy . In addition,
it was found that the added mass coefficient could vary significantly
from negative values to large positive values around the true reduced
velocity Vr = 5.9. These measured hydrodynamic coefficients resulted
in an accurate prediction of the rigid cylinder VIV in the CF direction(Wang et al., 2003), and they have served as databases for fluid forces insemi-empirical flexible riser VIV prediction codes (Roveri et al., 2001,
Triantafyllou et al., Zheng et al. et al.,2001, 1999, Larsen, 2001).
VIV of flexible bodies is significantly more complex than VIV of rigidbodies. Studies have been conducted to investigate the flow structureinteraction of flexible bodies undergoing VIV and revealed very complex
behaviors, including various structural modes, responses of travelingwaves, and recently multi-modal and multi-frequency vibrations.
Insights on the flow past the bodies’ wakes, in which boundary layers,
shear layers, vortices, and the bodies themselves interact, have been
revealed (Fan et al., 2019, Han et al., 2018). Given the flexible nature

Unlike the simple harmonic motion, studies find that VIV can occur
across a wide range of oscillating frequencies (Govardhan et al., 2002),
known as the “lock-in” range, in which synchronization between vortex

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