A Cantilevered Extensible Beam in Axial Flow: Semigroup Well-posedness and Post-flutter Regimes

TL;DR

This paper analyzes the mathematical well-posedness and dynamic behavior of a cantilevered beam in axial flow, focusing on flutter instability, with new results on nonlinear semigroup solutions and post-flutter regimes.

Contribution

It establishes well-posedness of a nonlinear beam model with rotational inertia and explores post-flutter dynamics using numerical methods.

Findings

Proved nonlinear semigroup well-posedness with rotational inertia.

Established existence of weak solutions without rotational inertia.

Numerically characterized post-flutter regimes and stability boundaries.

Abstract

We consider a cantilevered (clamped-free) beam in an axial potential flow. Certain flow velocities may bring about a bounded-response instability in the structure, termed {\em flutter}. As a preliminary analysis, we employ the theory of {\em large deflections} and utilize a piston-theoretic approximation of the flow for appropriate parameters, yielding a nonlinear (Berger/Woinowsky-Krieger) beam equation with a non-dissipative RHS. As we obtain this structural model via a simplification, we arrive at a nonstandard nonlinear boundary condition that necessitates careful well-posedness analysis. We account for rotational inertia effects in the beam and discuss technical issues that necessitate this feature. We demonstrate nonlinear semigroup well-posedness of the model with the rotational inertia terms. For the case with no rotational inertia, we utilize a Galerkin approach to establish existence of weak, possibly non-unique, solutions. For the former, inertial model, we prove that the associated non-gradient dynamical system has a compact global attractor. Finally, we study stability regimes and {\em post-flutter} dynamics (non-stationary end behaviors) using numerical methods for models with, and without, the rotational inertia terms.