Theoretical and Numerical Investigation on Whipping Behavior of Flexible Pipes Considering Fluid-Structure Interaction Effect

To analyze the dynamic characteristics of flexible pipes in the whipping process, a dynamic model of flexible pipes whipping behavior is developed in this study. The model is established upon the Euler-Bernoulli beam theory and incorporates the thrust force exerted at the rupture position. Furthermore, a fluid-structure interaction numerical model is developed for the purpose of analyzing the dynamic response of the whipping behavior. The theoretical and numerical results are utilized to investigate the effects of operating pressure, pipe length and Young’s modulus on the natural frequencies and dynamic characteristics. It is found that an increase in flow velocity has a considerable influence on the natural frequencies. As the flow velocity increases, the state of flexible pipes in the whipping process undergoes a transition from a stable state to a state of static and dynamic instability. The dynamic response is periodic, with a dominant frequency that is in close proximity to the natural frequency of the second mode. As the operating pressure and pipe length increase, the whipping behavior exhibits chaotic characteristics and the displacements increase significantly. A reduction in Young’s modulus results in a decrease in both natural frequencies and displacements, which consequently gives rise to an increase in the complexity and chaotic nature of the whipping behavior.