The Estimation of the Unsteady Aerodynamic Force Applied to a Turret in Flight

Abstract

The spatially-temporally-resolved pressure field on a surface of a hemisphere-on-cylinder optical turret was characterized in a wind tunnel at M = 0.33 using fast-response Pressure Sensitive Paint (PSP), simultaneously with 8 pressure sensors. A sparse unsteady pressure field was also obtained in-flight for subsonic speeds of M = 0.5 on the Airborne Aero-Optical Laboratory (AAOL) using 26 unsteady pressure sensors. Using the unsteady pressure data from PSP tests, the unsteady forces acting on the turret in the tunnel were calculated and discussed for different turret geometries and window viewing angles. Unsteady forces and moments acting on the turret in-flight were estimated using Linear Stochastic Estimation for different turret geometries and speeds and compared to the tunnel results. Using Proper Orthogonal Decomposition dominant surface pressure modes responsible for unsteady forces were identified and discussed.