Reduced order modeling of flow over a NACA 0015 airfoil for control application

Reduced order models that can capture and predict general flow characteristics are essential for closed-loop flow control around aerodynamic bodies. This research tests Galerkin based reduced order models using a proper orthogonal decomposition method to obtain a set of modes derived from experimental data to predict the flow over a NACA-0015 airfoil. Three methodologies are used to derive the models: the original POD Galerkin projection method, a modified version that includes a viscous dissipation term, and a new approach that uses a transfer parameter term to adjust the POD modes. Each of the models is tested on the airfoil at incident angles ranging from α=20 degree; to α=10 degree for the baseline flow and a flow forced at 1250 Hz by nanosecond dielectric barrier discharge plasma actuators. The results showed that the two modified reduced order models were most successful in predicting the time evolution coefficient using between 8 and 12 POD modes for their calculations. At this point, there was no clear indication that one method worked better than the other for the baseline or forced flow, or for a particular angle of attack of the airfoil. The behavior of the transfer parameter versus the angle of attack was investigated in order to find a predictable trend that would reduce the overall computational time, but no clear trend has been observed at this point.