Investigation of turbulent shock boundary interaction unsteadiness and its effects on aero-optics in a Mach 2 ramp flow

Abstract

Unsteady shock effects are investigated in a Mach 2 compression ramp in order to better understand the effects of shock motion on optical propagation. A shock surface is constructed from instantaneous flow data and used to determine the shock motion. This shock surface is then compared to the differential tip in the optical propagation in order to separate out the effects of the shock and the non-equilibrium boundary layer between the shock and ramp wall. The results show that even for a low Reynolds number (Re θ = 1375), the low frequency oscillations still show a characteristic Strouhal number of 0.03 which has been observed over a large range of Mach numbers at higher Reynolds numbers. Despite a marginal correlation between the wall pressure and the shock displacement, it is shown that using the wall pressure to drive Plotkin's simplified model of the shock motion [AIAA J., 13:8, 1975] has a much better correlation with the actual motion.

Numerical Simulation Exploring Supersonic Flow Over a Forward-Facing Cylindrical Step

“…The high-fidelity LES approach has been previously described in References 6 and 7. This LES methodology uses the discriminating low-pass filter operator that provides regularization in turbulent flow regions in lieu of a standard subgrid-scale (SGS) model and has been successfully used for multiple high fidelity LES/DNS simulations [8][9][10][11][12] including cases with supersonic flow [13][14][15] and flow control. 16 Additionally, the F DL3DI solver has successfully integrated an empirical plasma model proposed by Shyy et al 17 to trip the laminar boundary layer.…”