A single van der pol wake oscillator model for coupled cross-flow and in-line vortex-induced vibrations. (15th January 2020)

• Record Type: Journal Article
• Authors: Qu, Yang; Metrikine, Andrei V.
• Is Part Of: Ocean engineering. Volume 196(2020)
• Publication Date: 2020-01-15
• Subjects: Vortex-induced vibration -- Coupled cross-flow and in-line vibration -- Wake oscillator model -- Fluid-structure interaction journal: ocean engineering; Ocean engineering -- Periodicals; Ocean engineering; Periodicals; 620.4162
• DOI: 10.1016/j.oceaneng.2019.106732
• Languages: English
• ISSNs: 0029-8018

Abstract

Abstract: 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. Highlights: An advanced single wake oscillator model for the prediction of coupled cross-flow and in-line vortex-induced vibrations of cylinder is presented. A new in-line coupling term has been introduced. The model captures important characteristics of coupled cross-flow and in-line vortex-induced vibrations. Numerical and experimental results are in good agreements.