Towards Effective Characterization of the Normal Force Curve in Transverse Galloping

The past decade has witnessed a renewed interest in studying the fundamentals of galloping due to the emergence of new engineering applications were this aeroelastic instability is intentionally activated and utilized. One interesting problem deals with the development of analytical models to predict the dependence of the galloping instability on the parameters of the flow and the geometry of the galloping body. In this regard, most of the mathematical models used to predict the onset of galloping rely on experimental identification techniques to characterize the aeroelastic forces at play. One common approach adopts the quasi-steady flow theory and identifies the aerodynamic forces by using static wind-tunnel measurements in which the bluff body is rotated relative to the flow direction and the forces are measured at different angles of attack. This approach necessitates collecting a large number of data points at different angles of attack to characterize the aeroelastic forces acting on a single bluff body. To alleviate this problem, this paper proposes a new approach, which utilizes measurements of the time history of the bluff body oscillations combined with a balance of the interacting energy fields to estimate the normal force coefficient in galloping oscillators. A key advantage of the proposed method lies in its ability to rapidly and accurately predict the normal force curves using a single set of time history data and without the need to use complex and sometimes not very sensitive force measurements. The method is verified experimentally and used to effectively predict the normal force curves for a set of bluff geometries.