Improved Flutter Boundary Prediction for an Isolated Two-Degree-of-Freedom Airfoil

A novel method of computing the flutter boundary for an isolated airfoil based on a high-fidelity CFD model reveals unusual behavior at certain Mach numbers for a NACA 0012 section. Inviscid and viscous predictions of the flutter boundary for the two airfoils are compared with results from a previous experimental study. Over a narrow range of Mach numbers, unusual aeroelastic response behavior occurs, and inviscid and viscous predictions dier significantly. Also in this range, solutions show increased sensitivity to grid topology as well as flow Mach number. This is found to be a consequence of flow shedding which occurs over a narrow range of Mach numbers. The nature of this shedding is captured only by using a greatly refined viscous grid, and unusual numerical results occur when using coarser viscous and inviscid meshes.