A Parametric Investigation of Oblique Shockwave / Turbulent Boundary Layer Interaction Using LES

摘要

Large-eddy simulation (LES) of an oblique shock impinging on a supersonic turbulent boundary layer (M_∞ = 2.28, φ = 6.5-9.5°, Re_θ = 1500, 2300, 4800) is carried out with a high-order compact differencing scheme using localized artificial diffusivity (LAD) for shock capturing. Solution sensitivity is then investigated with regards to mesh resolution, domain size, Reynolds number, and wedge angle. Progressive mesh refinement and comparison with the literature are used to establish confidence in solution quality. It is found that the separation bubble is not significantly affected by increasing the spanwise domain beyond 3δ or by increasing the streamwise domain beyond 55 past the shock impingement point. Additionally, the size of the separation bubble, while under-predicted with respect to experiment, does not appear to be significantly affected by Reynolds number (over the range considered). This leads us to speculate that a commonly observed discrepancy between simulation and experiment - which previously has been explained as a result of difference in Reynolds number - may instead be due to some three-dimensional effect in the experiment. Additionally, through analysis of the spectral content of the wall pressure signal in the separation bubble, the expected low-frequency motion is identified with time scale ～O(100δ/u_∞); however, it appears that Reynolds number, while having little effect on the size of the mean separation bubble, may affect the time scale at which low-frequency unsteadiness is observed. Likewise, it is found that an increase in wedge angle tends to shift the peak low-frequency energy out towards longer time scales. Finally, through analysis of low-pass filtered data fields, evidence is found of a correlation between the low-frequency motion and periodic mass entrainment/release in the separation bubble.