Nonlinear dynamics of viscoelastic pipes conveying fluid placed within a uniform external cross flow

This paper investigates the nonlinear dynamic response of a viscoelastic pipe conveying fluid subjected to a uniform external cross flow based on the Euler-Bernoulli theory. The main objective of this work is to find the proper viscoelastic coefficients to mitigate the dynamic response of a marine riser. A nonlinear oscillator is utilized to simulate the mean drag force and the vortex-induced lift force. Also, the pipe material is assumed to be viscoelastic and consisted of the Kelvin-Voigt type. The extended Hamilton's principle along with the Galerkin discretization are employed to construct the nonlinear model of the coupled fluid-structure system. Moreover, the assumed mode method along with the Runge-Kutta integration algorithm is used as a solution method. The results from the developed numerical model are verified with those available in the literature. Then, the effects of internal fluid velocity, external fluid reduced velocity and viscoelastic damping on the vibration amplitude of the pipe are examined. It is noted that, when lock-in phenomena occur, the internal fluid velocity and viscoelastic damping have vital effects on the vibration amplitude and the lock-in region range of the pipe. It is however demonstrated that employing a proper viscoelastic material may lead to eliminating jump phenomenon.