Collaborative project with the Politecnico di Milano produces valuable insight into the flow field around the flapping flag

August 20, 2013


Milan, Italy. August, 20, 2013

Limit Cycle Oscillation of the Flapping Flag

This past summer Ph.D. candidate Chad Gibbs (Duke B.A. 2010, Duke M.S. 2012) traveled to Milan, Italy to conduct a collaborative research project with researchers at the Politechnico di Milano. The goal of the trip was to explore the flow field around the flapping flag aeroelastic system using a Particle Image Velocimitry (PIV) system installed on the Politechnico wind tunnel.

The flapping flag is a term used to describe a cantilever plate with flow along its elastic axis. This system exhibits a flutter instability when the flow velocity increases above a critical velocity. The structure then enters a large and violent Limit Cycle Oscillation (LCO) that depends on the non-linearities in the fluid and elastic structure. The literature contains extensive explorations of this system, but a complete understanding of the dynamics, especially in the post-flutter LCO regime remains elusive. Understanding the post-flutter response of the flapping flag is especially important in light of the applications of the phenomenon that include using a flapping flag for energy harvesting, autonomous vehicle propulsion,and as a way to explain human snoring.

By using PIV methods, the research team was able to quantify the flow field during the LCO and suggest how researchers can improve fluid models to capture more accurately the aerodynamic features of the flow field. The research has been submitted as a brief note to the Journal of Fluids and Structures

Flow Field around the Flapping Flag