Abstract
In this paper, the impact of buoyancy modules aspect ratios and arrangement on the VIV response of a power cable or riser is addressed through a dual approach coupling experimental and numerical simulations.
Two sets of experiments are performed in the ‘South France – Ocean Basin’ located in La Seyne-Sur-Mer and operated by Océanide. On the first one, rigid sections of pipe equipped with a single buoyancy module are submitted to a pure harmonic crossflow oscillation with over imposed steady flow conditions. From load measurements on the buoyancy modules themselves, a database of hydrodynamic coefficients for several aspect ratios is obtained. Then, the VIV response of a line installed across the basin and fitted with different buoyancy module arrangements was tracked to investigate the impact of buoyancy module aspect ratio, as well as their arrangement.
The data extracted from the second set of tests is used as a benchmark case to validate the numerical approach via Shear 7. Both the default hydrodynamic data from the software and the hydrodynamic database obtained from the first set of tests are compared.
A weaker power input from the buoyancy modules was found compared to the expected results for an infinite cylinder, as well as a possible modification of vortex shedding frequency (Strouhal number). When focusing on the buoyancy module arrangement, the experimental results emphasize the impact of gap between buoyancy modules on the global cable response. Moreover, this experimental/numerical benchmark provides some insight on the validity of the simplified approach of software as Shear7 for this type of riser or power cable configuration.
