Fluid nonlinearities effect on wake oscillator model performance.

Kurushina, Victoria; Pavlovskaia, Ekaterina

Abstract

Vortex-induced vibrations (VIV) need to be accounted for in the design of marine structures such as risers and umbilicals. If a resonance state of the slender structure develops due to its interaction with the surrounding fluid flow, the consequences can be severe, resulting in accelerated fatigue and structural damage. Wake oscillator models allow us to estimate the fluid force acting on the structure without complex and time-consuming CFD analysis of the fluid domain. However, contemporary models contain a number of empirical coeffcients that must be tuned using experimental data. This is often left for future work, with the open question of how to calibrate a model for a wide range of cases, and how to find out what is working and what is not working. The current research is focused on the problem of the best choice of the fluid nonlinearities for the base wake oscillator model [1], in order to improve the accuracy of prediction for the cases with mass ratios around 6.0. The paper investigates six nonlinear damping types for two fluid equations of the base model. The calibration is conducted using the data by Stappenbelt and Lalji [2] for two degrees-of-freedom rigid structure for mass ratio 6.54. The conducted analysis shows that predicted in-line and cross-flow displacements are more accurate if modelled separately using different damping types, rather than using only one version of the model. The borders of application for each found option in terms of mass ratio are discussed in this work and appropriate recommendations are provided.

Citation

KURUSHINA, V. and PAVLOVSKAIA, E. 2018. Fluid nonlinearities effect on wake oscillator model performance. In Manoach, E., Stoykov, S. and Wiercigroch, M. (eds.) Proceedings of the 2017 International conference on engineering vibration (ICoEV 2017), 4-7 September 2017, Sofia, Bulgaria. MATEC web of conferences, 148. Les Ulis: EDP Sciences [online], paper number 04002. Available from: https://doi.org/10.1051/matecconf/201814804002

• Conference Name: 2017 International conference on engineering vibration (ICoEV 2017)
• Conference Location: Sofia, Bulgaria
• Start Date: Sep 4, 2017
• End Date: Sep 7, 2017
• Acceptance Date: Sep 4, 2017
• Online Publication Date: Feb 2, 2018
• Publication Date: Feb 2, 2018
• Deposit Date: Feb 13, 2024
• Publicly Available Date: Feb 29, 2024
• Publisher: EDP Sciences
• Series Title: MATEC web of conferences
• Series Number: 148
• Series ISSN: 2261-236X
• DOI: https://doi.org/10.1051/matecconf/201814804002
• Keywords: Vibration; Fluid dynamics; Wake oscillation; Marine engineering
• Public URL: https://rgu-repository.worktribe.com/output/2166786