Predicting the operability limit of the HyShot II scramjet using LES

The present work is part of a broad effort toward predictive simulations of com-plex multi-physics flows at high Reynolds numbers. The main objective of the Stanford PSAAP Center (Predictive Science Academic Alliance Program) is to predict the react-ing flow in the HyShot II scramjet experiment carried out in the High Enthalphy shock tunnel at Göttingen (HEG) facility of the German Aerospace Agency DLR (cf. Gardner et al. 2004; Laurence et al. 2012). Specifically, the objective is to predict the best-estimate of the flow, to estimate the uncertainties from a range of sources in this prediction and, finally, to quantify the margin to engine unstart. Scramjet combustors are designed to use the heat added from combustion to cause an increase in pressure, which, when expanded in a nozzle, causes thrust. At nominal conditions, the HyShot II is designed to have essentially attached flow throughout the combustor, with a smooth (not counting the many oblique shock waves) rise in pressure throughout. If too much fuel is injected, leading to excessive heat addition, the flow may become choked; this would initiate an unsteady “unstart ” process, eventually resulting in subsonic flow throughout the combustor and complete loss of thrust. This failure mod