Nonlinear vortex-induced vibration of a complex confined fluid transport pipeline with nonlinear energy sink

This study investigates the influence of nonlinear energy sink (NES) on the vortex-induced vibration (VIV) characteristics of axially-tensioned pipelines subjected to external fluid flow, with special attention to the complex constraints imposed by torsional effects and support spring systems. The nonlinear governing equations are derived based on the Van der Pol equation model and the Hamilton principle. The Gauss-Legendre method and the differential quadrature method are used to get the numerical mode. The nonlinear coupled motion equation is discretized using the numerical model and fourth-order Galerkin method, and then solved using the fourth-order Runge-Kutta method. The findings indicate that adding NES and increasing its damping effectively raises the first-order natural frequency, creating favorable conditions for vibration mitigation. The introduction of the NES significantly mitigates the system's second instability state. Analysis reveals that the maximum response amplitude of the system configured with an NES is reduced by a significant margin in contrast to the system without it. The incorporation of the NES effectively mitigates certain chaotic movements.