Cantilevered pipe ejecting fluid under VIV: an investigation based on a planar nonlinear reduced-order model

This paper aims to investigate the use of the modular modeling methodology for deriving mathematical models for a class of problems hardly treated in the fluid–structure interaction literature: the combined effects of internal and external flow in a slender flexible pipe. As first attempt to address this issue, this paper proposes a planar nonlinear reduced-order model for a submerged cantilevered pipe ejecting fluid under VIV. The adopted strategy has already proved to be very effective for the corresponding problems in which only internal flow effects are considered. Within this methodology, not only subsystems might be treated individually but also, in the first approach, compatibility conditions can be relaxed and nonlinear terms can be replaced by redundant variables, once an algorithm allows to enforce constraints a posteriori. Such a modular approach proves to be particularly adequate for coupling, under the adopted hypotheses, phenomenological nonlinear wake oscillator models to the previously introduced formulation for the pipe ejecting fluid. Numerical simulations provide further discussions on the response of the nonlinear reduced-order model proposed.