Modal vibration modeling of a hemispherical turret in subsonic flow

Airborne beam propagation systems operate in high-jitter environments, where a significant contributor, known as aero-mechanical jitter, originates from unsteady aerodynamic forcing on the beam director. In this study, we investigate the aero-mechanical response of a hemispherical turret by simultaneously measuring optical jitter, surface pressure, and structural vibrations. A simplified turret geometry was designed to isolate key jitter mechanisms, and both experimental and numerical modal analysis were used to characterize the system vibration. Wind tunnel tests at subsonic Mach numbers were conducted with the turret mounted both inside and outside the tunnel to separate aerodynamic and structural contributions. To isolate key mechanisms, a simplified turret geometry with well-characterized material properties is employed. A reduced-order modal model is developed to connect surface pressure fluctuations to structural vibration and resulting beam jitter. This framework provides insight into the coupling between aerodynamic loading and optical stability, enabling more predictive jitter modeling for airborne optical systems.