An experimental study of the spanwise correlation of vortex shedding in the towing tank

Abstract

Although there are many correlation studies dedicated to the vortex shedding of cylinders in wind tunnels, the experiments conducted in water have not been carried out well before, especially for the flexible cylinder. In order to investigate this area, the present experiment was conducted in a towing tank and both the rigid and flexible cylinders were used. Various results are obtained including the correlation coefficients, correlation lengths and probability distribution, which exhibit several valuable features. Firstly, the correlation coefficients of the flexible cylinder are more irregular than that of the rigid cylinder. Secondly, the correlation lengths have visual peaks at Re ≈ 5.0 ∼ 6.0 × 10³ for both the rigid and flexible cylinders, and a sharp decrease after this region should involve the inception of vortex dislocations. In addition, the analysis of root mean square and probability density function of the phase drift gives more insights of the vortex shedding along the spanwise different cross-sections.

Keywords:

• correlation length
• riser
• vortex-induced vibration
• model test

Acknowledgements

The authors thank the Brazilian National Research Council (CNPQ) and the National Basic Research Program of China (973 Program) Grant No. 2011CB013702 for the financial support to this research.