A Numerical Model of Vortex-Induced Vibration on Marine Risers

The Steger and Warming flux vector splitting implicit scheme is used to numerically solve two dimensional Reynolds Averaged Navier–Stokes (RANS) equations governing the vortex induced vibration of a flexible riser laterally supported by a spring and a damper. The k–ε model is used as turbulence model to simulate the turbulent flow in the wake of the riser. To update the new position of the riser, the lift coefficient obtained from the previous RANS iteration is coupled by the body motion equation. The proposed numerical solution is able to provide fair results in terms of lift coefficient, amplitude of oscillation and the effect of reduced velocity on it. The numerical results are compared with the available experimental and computational data where fairly good agreement even at the lock-in regime has been obtained. Taking wider external boundary, using conservative form of the equations, applying k-ε turbulence model for the separated flow and finally using the variable time step as the lock-in region approaches, are main features of the proposed numerical model.

Keywords:

vortex-induced vibration , RANS equation , turbulence model , lift coefficient