Flutter analysis of airfoil using fluid structure coupling based on Euler equations

Aero-elasticity is the subject that describes the interaction between the deformation of an elastic structure in airstream and resulting aerodynamic force especially on aircrafts. This work studies the numerical analysis of the airfoil flutter. To do this work, Euler equations are integrated in time to get aerodynamic forces, then, at each time step, these aerodynamic forces are coupled with airfoil equations of motion to simulate its flutter. Two numerical techniques are used in this work ; McCormack’s technique to evaluate aerodynamic forces, and Newmark’s technique to evaluate airfoil dynamic response. MATLAB program was developed for implementation of these techniques. For solution verification and validation, the work was implemented on NACA 0012 airfoil because of availability of its section parameters and aero-elastic characteristics. Most previous researches on flutter didn’t focus on two important flutter points. The first point is the numerical error produced in flutter velocity when using low coupling frequency (CFD-CSD). The second point is flutter velocity obtained by classical method is so close to that obtained by using sophisticated codes like Euler equations. As a result, the two cases have been investigated in the next pages and results presented : (I) Substantial error at using long coupling step (with time step=0.002s flutter velocity=174m/s, with time step=0.01s flutter velocity=166.8m/s). (II) Classical method can be used as first estimation of flutter because it give tolerable results (flutter velocity based classical=175m/s, flutter base Euler equations=174m/s).