Experimental investigation of suppression of vortex-induced vibration of marine risers by three control rods

Vortex-induced vibration(VIV) of marine risers may significantly increase threats of structural fatigue failure.In order to suppress VIV,an effective passive flow control method is proposed in this work,which is accomplished by arranging three identical small circular cylinders close to the riser model with 120° angle.The riser model with control rods is placed in a water flume subject to four different current velocities and two extreme attack angles.The experimental results show that the control rods can remarkably reduce the transverse responses of the riser model while the vibration frequency of the riser model is almost the same as that of a bare riser.The experiments also demonstrate that the present flow control measure is not sensitive to the incoming flow direction,which is a very important advantage for practical engineering application.