Dynamics of spinning pipes conveying a variable-density fluid

In this study, the dynamical behavior of spinning pipes conveying fluid of axially variable density is investigated. First, based on Hamilton's principle, the coupled governing equations for flexural vibration of the pipe system are derived. Then, the motion equations are truncated by using the Galerkin method. As a result, the discretized motion equations as well as the eigenfrequency equations of the system are obtained. The natural frequencies, divergence, and flutter instability thresholds of the fluid–structure interaction system are acquired by computing the complex frequencies in the first two modes of the system. Also, a comparative study is conducted to validate the accuracy of the present model and solution approach. Finally, the effects of main parameters, such as spinning velocity, flow velocity, mass ratio, and fluid density gradient parameter, on the vibration and stability of the pipe system are evaluated. The results show that the stability of the pipe system is dominated by the mass ratio and the fluid density gradient parameters, while the spinning velocity mainly affects the natural frequency of the system.