Experimental Measurements of an Aircraft-Mounted Pod Concept for Improved Aero-Optic Performance

Experimental data are presented for a wind-tunnel model of an aircraft under-wingmounted pod. The pod model was designed to prevent or mitigate aero-optic aberrations around an optical aperture in a turret ball at the nose of the pod. In particular, the model incorporated a “virtual duct” around the optical aperture, in which fences are attached to the spherical surface of the turret ball and shaped to modify the flow around the turret so as to prevent flows that are known to cause severe optical aberrations. Pressure data are presented that closely compare with inviscid CFD computations, and that indicate that the virtual-duct approach successfully prevents flow separation on the rear of the turret ball. The experimental data also show that the fences of the virtual duct significantly increase the critical Mach number at which supersonic flow and shock formation would occur on the turret ball.