TY - JOUR
T1 - A single van der pol wake oscillator model for coupled cross-flow and in-line vortex-induced vibrations
AU - Qu, Yang
AU - Metrikine, Andrei V.
N1 - Accepted Author Manuscript
PY - 2020
Y1 - 2020
N2 - In this study a new wake oscillator model is proposed to describe the coupled cross-flow and in-line vortex-induced vibrations of an elastically supported rigid cylinder. Different from many other studies where two wake oscillators have been applied, the current model uses only one wake oscillator coupled to both cross-flow and in-line motions. The new model is based on the van der Pol oscillator with the classic acceleration coupling between the wake and cross-flow motion, while the in-line motion is coupled with the wake variable in a nonlinear manner. The predictions of this new model are compared with the existing experimental data and shown to be in good agreement. In addition to the conventional lock-in range that corresponds to reduced velocities between 5 and 8, another lock-in is predicted around reduced velocity of 2.5 due to the in-line vibration. Most importantly, the new model is proved to be able to predict the appearance of the ‘super-upper’ branch at small mass ratios without changing the tuning parameters. The limitations of the model associated with unrealistic predictions of free vibrations with very small mass ratios and those of forced in-line vibrations at high frequencies are also discussed along with a possible remedy.
AB - In this study a new wake oscillator model is proposed to describe the coupled cross-flow and in-line vortex-induced vibrations of an elastically supported rigid cylinder. Different from many other studies where two wake oscillators have been applied, the current model uses only one wake oscillator coupled to both cross-flow and in-line motions. The new model is based on the van der Pol oscillator with the classic acceleration coupling between the wake and cross-flow motion, while the in-line motion is coupled with the wake variable in a nonlinear manner. The predictions of this new model are compared with the existing experimental data and shown to be in good agreement. In addition to the conventional lock-in range that corresponds to reduced velocities between 5 and 8, another lock-in is predicted around reduced velocity of 2.5 due to the in-line vibration. Most importantly, the new model is proved to be able to predict the appearance of the ‘super-upper’ branch at small mass ratios without changing the tuning parameters. The limitations of the model associated with unrealistic predictions of free vibrations with very small mass ratios and those of forced in-line vibrations at high frequencies are also discussed along with a possible remedy.
KW - Coupled cross-flow and in-line vibration
KW - Fluid-structure interaction journal: ocean engineering
KW - Vortex-induced vibration
KW - Wake oscillator model
UR - http://www.scopus.com/inward/record.url?scp=85077087143&partnerID=8YFLogxK
U2 - 10.1016/j.oceaneng.2019.106732
DO - 10.1016/j.oceaneng.2019.106732
M3 - Article
AN - SCOPUS:85077087143
VL - 196
JO - Ocean Engineering
JF - Ocean Engineering
SN - 0029-8018
M1 - 106732
ER -