Numerical Analysis of Optical Path Difference for Oblique Shockwave on a Wedge

Freestream density varies within and after an oscillating weak oblique shockwave and can cause significant optical path difference (OPD) within a laser beam propagation. Unsteady numerical simulations were performed to provide a comprehensive understanding of this complex flow phenomenon, particularly the frequency spectrum of this oblique shockwave from a 20° wedge. The hybrid RANS/LES turbulence model was used in this study and compared to experimental data conducted at the Aero-Effects Lab (AEL) at the Air Force Research Laboratory at Kirtland Air Force Base, NM. In addition due to the side effects of wedge, expansion waves were observed from the numerical simulation. These flow features were shown to have a significant impact on the frequency spectrum of the oblique shockwave. The edges of the wedge model were replaced with a half-cone configuration to reduce the presence of the expansion waves. Numerical results showed that the peak frequency has increased with this alternative wedge geometry, which indicates that the expansion waves from the edges of the wedge damped the frequency content of the oblique shockwave.