van der Pol-Duffing Modeling for Torsional Galloping

Abstract

This study is a continuation of the study presented in OMAE 2012 entitled: “Stability Analysis of a Yawing Flat Plate into the Water Current”[1]. The structure in the aforementioned study consists of a rectangular flat plate with an elastic axis in its mid-chord length. The elasticity is provided by torsion spring. The flat plate has only one degree of freedom which is angular oscillation about its axis. It is observed that as the current speed exceeds a critical velocity, the flat plate becomes unstable. The instability leads to torsional galloping occurrence, as a result of which the flat plate begins to oscillate angularly about the elastic axis. Through the present study, a phenomenological model is developed based on van der Pol-Duffing equation, in order to explain the instability leading to the torsional galloping.