Flow physics and RANS modelling of oblique shock/turbulent boundary layer interaction

Abstract

Large-eddy simulation (LES) is utilized to investigate flow physics and lower-fidelity modelling assumptions in the simulation of an oblique shock impinging on a supersonic turbulent boundary layer (OSTBLI). A database of LES solutions is presented, covering a range of shock strengths and Reynolds numbers, that is utilized as a surrogate-truth model to explore three topics. First, detailed conservation budgets are extracted within the framework of parametric investigation to identify trends that might be used to mitigate statistical (aleatory) uncertainties in inflow conditions. It is found, for instance, that an increase in Reynolds number does not significantly affect length of separation. Additionally, it is found that variation in the shock-generating wedge angle has the effect of increasing the intensity of low-frequency oscillations and moving these motions towards longer time scales, even when scaled by interaction length. Next, utilizing the LES database, a detailed analysis is performed of several existing models describing the low-frequency unsteady motion of the OSTBLI system. Most significantly, it is observed that the length scale of streamwise coherent structures appears to be dependent on Reynolds number, and at the Reynolds number of the present simulations, these structures do not exist on time scales long enough to be the primary cause of low-frequency unsteadiness. Finally, modelling errors associated with turbulence closures using eddy-viscosity and stress-transport-based Reynolds-averaged Navier–Stokes (RANS) simulations are investigated. It is found that while the stress-transport models offer improved predictions, inadequacies in modelling the turbulence transport terms and the isotropic treatment of the dissipation is seen to limit their accuracy.

Instabilities in oblique shock wave/laminar boundary-layer interactions

“…In particular, this link seems to have a nonlinear origin consistent with the results given by Sansica et al (2014). An interesting synthesis of these different scenarios is given by Morgan et al (2013).…”

A Non-Equilibrium Wall-Model for LES of Shock/Boundary Layer Interaction at High Reynolds Number

“…While not seen in the experiments (likely due to the uncertainty associated with the extrapolation procedure), we note that a very similar sudden decrease in C f at the the shock-induced separation was also observed in both the DNS by Pirozzoli and Bernardini [33] and the wall-resolved LES by Morganet al [34]. In addition, both these highly resolved studies showed similar dips in C f at the beginning and end of the low-friction plateau-region as seen in the present results.…”

Unsteady effects of strong shock-wave/boundary-layer interaction at high Reynolds number

“…Touber & Sandham (2009) were probably among the first to publish a successful comparison between their long-time (10 4 δ 0 U 0 ) narrow-domain LES results and experimental data with respect to the unsteady shock motion. Further LES studies for impinging SWBLI with a focus on low-frequency aspects of the interaction have been published thereafter (Pirozzoli et al 2010;Hadjadj 2012;Agostini et al 2012;Aubard et al 2013;Morgan et al 2013;Pasquariello et al 2014;Nichols et al 2016). All of these studies, however, predominantly focused on weak interactions (with respect to the absence of a distinct pressure plateau within the separated flow) and/or low Reynolds numbers being typically below Re δ0 ≈ 60 ⋅ 10 3 .…”