High Fidelity Approaches for Pitch Damping Prediction at High Angles of Attack

Abstract

The capability of accurately estimating pitch-damping values for missilelike geometries over a range of Mach numbers and at high angles of attack using state-of-the-art computational-fluid-dynamics techniques has been investigated. Toward this effort, three geometries were examined: the Army–Navy Finner model, the extended Army–Navy Finner model, and the M823 research store. Pitch-damping values are predicted using forced-oscillation calculations performed with the RavenCFD Navier–Stokes flow solver. Additionally, pitch-decay calculations and aerodynamic build-up methods are also employed using the RavenCFD solver. These methods are compared to both experimental results and AP09, a fast-running engineering tool. Pitch-damping variations due to geometric changes, Mach number changes, and angle-of-attack changes are explored with each method. Overall, each computational-fluid-dynamics method exhibits an outstanding agreement with experiment and range data at the lower angles of attack. Both pitch-decay and forced-oscillation approaches provide good agreement for low-to-moderate angles. At angles of attack greater than 30 deg, the forced-oscillation approach provides the best agreement. Pitch-damping variations at angles higher than 60–70 deg for the Army–Navy Finner have been shown to be a peripheral effect of the extreme unsteadiness of the wake flow at these conditions.