Computational Investigation of Subsonic Torsional Airfoil Flutter
NAVAL POSTGRADUATE SCHOOL MONTEREY CA
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In this thesis single-degree-of-freedom torsional airfoil flutter is investigated using an incompressible potential flow code, a compressible inviscid Euler code and a compressible viscous Navier-Stokes code. It is found that the classical linearized incompressible and compressible flow theories yield unconservative flutter estimates. The computations based on the non-linear codes show for NACA 0006, NACA 0009, NACA 0012 and NACA 0015 airfoils, that the regions of torsional flutter instability increase as the airfoil thickness and the flight Mach number is increased. On the other hand, the comparison of the flutter boundaries computed with the viscous Navier-Stokes code versus the inviscid Euler code shows that the effect of viscosity is stabilizing. Also, the computed flutter boundaries display the effect of pitch axis location on flutter. Axis locations in the range between half a chord upstream of the leading edge of the airfoil and the leading edge are most prone to induce flutter. Axis locations downstream of the quarter chord are flutter free.
- Fluid Mechanics