Post-flutter characteristics and flow-driving mechanisms in flexible photovoltaic structures based on proper orthogonal decomposition

Flexible photovoltaic structures (FPSs) are increasingly used in large-span solar installations, but their low stiffness makes them vulnerable to wind-induced flutter under strong wind conditions. This work investigates the post-flutter characteristics of FPSs using computational fluid dynamics simulations. Proper orthogonal decomposition (POD) is employed to systematically analyze the coherent flow structures and surface pressure modal characteristics during the limit cycle oscillation (LCO) stage. Accordingly, aerodynamic work analysis of POD modes is conducted to elucidate the underlying flow-driven mechanism from an energy transfer perspective. Results indicate that the post-flutter flow field is dominated by the leading-edge vortex (LEV) structure. The surface pressure mode induced by the LEV maintains a favorable phase relationship with the structural motion at the fundamental frequency, manifesting as negative aerodynamic damping and serving as the primary driving source sustaining the LCO. The second pressure mode exhibits an unfavorable phase relationship with the structural motion, thereby performing negative work on the system and limiting further amplitude growth. Increasing wind speed intensifies LEV evolution and causes the negative-pressure core of the dominant mode to extend downstream along the chord. The system compensates by increasing the phase lag, thereby achieving a new energy balance. A larger initial inclination angle reduces the phase difference between the dominant mode and structural motion, improving aerodynamic work efficiency. However, reverse pressure near the trailing edge induces load cancellation, weakens the overall aerodynamic excitation, and ultimately results in a lowerenergy LCO state with a smaller amplitude.