Non-Linear Dynamic Aerodynamic Coefficients for Aircraft

Determining the proper dynamic terms for aerodynamics math models representing fighter aircraft during high-angle-of-attack maneuvers is limited by the ability to quantify the necessary dynamic coefficients from either computations or experiments. The traditional approach uses small-amplitude forced-oscillation (assumes linear variation of  aerodynamic coefficients with rotation rate) and rotary-balance wind tunnel tests. Data from these experiments are then combined with various methods of superposition to approximate the actual flight response.

RHRC has uniquely acquired the appropriate static and dynamic force and moment data in RHRC's water tunnel with motions from one to three degrees of freedom in pitch, yaw, roll and velocity-vector roll without the usual constraints of assuming linear aerodynamics. Static experiments were performed to identify "critical states" in the flow field (such as rapid changes in forces due to vortex breakdown) which introduce dramatic departures from a locally linear aerodynamic behavior during certain maneuvers.

RHRC's water tunnel has the unique capability to perform multi-axis dynamic force/moment tests with simultaneously flow  visualization. RHRC used a 65 degrees delta wing model, which allows direct comparison to results from advanced wind tunnel to acquire non-linear dynamic data, and an F/A-18E model, a more complex configuration representing modern fighter aircraft.