Investigation on the vortex-induced vibration active control of the riser in the “lock-in” region based on adaptive fuzzy sliding mode theory

Abstract

A numerical simulation is proposed for the vortex-induced vibration of a riser with two degrees of freedom. The fluid–structure interaction is determined using FLUENT fluid-simulation software with the user-defined function embedded, giving the dynamic response and vortex shedding. The reduced velocity ranges between 1 and 13. An adaptive fuzzy sliding mode controller based on Simulink co-simulation was innovatively applied to the active control of vortex-induced vibration of the riser. The dynamic responses and wake patterns before and after the active control in the “lock-in” region were compared and analyzed, and showed that extremely severe vibration of the riser occurred when the reduced velocity was 5–6, when the vortex shedding frequency was close to the natural frequency and when reached the “lock-in” region. After applying the control, the vibration amplitude of the riser was suppressed with 95% efficiency in the cross-flow direction, and about 89% in the in-line direction. The adaptive fuzzy sliding mode controller demonstrated excellent control effects in both directions and is adaptable to the active control of vortex-induced vibration under different disturbance, mass/stiffness and velocity conditions.