A 3D Nonlinear Reduced-Order Model of a Cantilevered Aspirating Pipe Under VIV

Abstract

This chapter brings a 3D nonlinear reduced-order model of a vertical cantilevered flexible pipe aspirating the same fluid in which it is immersed and subjected to transversal external flow. The generalized extended Hamilton principle for non-material volumes is applied, and the effects associated to the external and internal flows, particularly at the pipe inlet, are properly considered. A wake-oscillator phenomenological model is adopted for the structure interaction with the external flow. Non-dimensional equations of motion are derived through the Modular Modeling Methodology. A root-loci analysis is presented, as a function of the flow aspiration speed, to guide choosing 2 simulation scenarios: just below and just above the first transition to instability, at small velocity. External flow velocity is considered over a range where the second mode of vibration is fully excitable by vortex shedding. In the chosen scenarios, the external flow action is dominant over that of the internal flow.