Aero-Optical Evaluation of Notional Turrets in Subsonic, Transonic and Supersonic Regimes

Abstract

The aero-optical performance of two notional turret designs, a hemisphere-on-plate and a submerged hemisphere-on-plate, are evaluated at Mach numbers ranging from purely subsonic, transonic, and supersonic using highly-resolved Detached Eddy Simulation (DES). The resolved density fluctuations in the flow fields are captured to compute the unsteady Optical Path Length (OPL) in propagation paths corresponding to a range of beam bearings and elevations. These OPL are processed to produce aperture-averaged wave front error, which are correlated to the different flow features produced around the turrets. In particular, the results show unsteady Shock Boundary Layer Interactions (SBLI), contact surface rollup and intense wake structures for the supersonic conditions. An unsteady transonic shock structure over the turret is observed at the transonic conditions. Large-scale vortical structures are observed in the wake for all Mach numbers. The effect of these various structures upon aero-optical performance is evaluated by comparing aperture-averaged wave front error for different beam bearings and elevations for the different notional turrets. Finally, the wave front error is correlated with unsteady flow features for each turret geometry.