Added mass variation effect on vortex-induced vibration for flexible risers based on force-decomposition model

ABSTRACT

Vortex-induced vibration (VIV) due to periodic vortex shedding around the cylindrical structures is a typical and complicated fluid-structure interaction issue. In this paper, an improved time domain numerical simulation model, which can take the variation effect of added mass into account, is proposed to predict VIV for flexible risers. Originated from forced vibration experimental data, a time-varying function of both response frequency and amplitude is used to describe hydrodynamic forces, and added mass coefficient is considered variable with response frequency. Modal analysis serving VIV hydrodynamic forces calculation is implemented at the beginning of each time step, and dominant frequency of every element will be updated based on real-time structural natural frequency. By validating with model tests of two flexible risers, the proposed model is proved to show better performance for VIV prediction than traditional method (assuming C_a = 1). The added mass variation effect on VIV is discussed qualitatively and quantitatively.

KEYWORDS:

• Vortex-induced vibration
• added mass
• variation effect
• modal analysis
• time domain

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This paper is based on the projects supported by the National Natural Science Foundation of China [grant number 51579146], [grant number 51490674]; Shanghai Rising-Star Program [grant number 16QA1402300]; Shanghai Municipal Natural Science Foundation [grant number 15ZR1423500].