Incident shock wave and supersonic turbulent boundarylayer interactions near an expansion corner. (15th February 2020)

• Record Type: Journal Article
• Authors: Tong, Fulin; Li, Xinliang; Yuan, Xianxu; Yu, Changping
• Is Part Of: Computers & fluids. Volume 198(2020)
• Publication Date: 2020-02-15
• Subjects: Shock wave -- Turbulent boundary layer -- Unsteadiness -- Expansion corner; Fluid dynamics -- Data processing -- Periodicals; 532.050285
• DOI: 10.1016/j.compfluid.2019.104385
• Languages: English
• ISSNs: 0045-7930

Abstract

Highlights: Expansion effects on the interactions are identified from DNS results. Size and three-dimensionality of separation bubble are significantly decreased. Souverein's [30] scaling analysis is modified to account for expansion effect. The low frequency unsteadiness is clearly suppressed at large expansion angle. Abstract: Direct numerical simulations of incident shock wave and supersonic turbulent boundary layer interactions near an expansion corner are performed at Mach number M ∞ = 2.9 and Reynolds number Re ∞ = 5581 to investigate the expansion effect on the characteristic features of this phenomenon. Four expansion angles, i.e. α = 0 0 (flat-plate), 2 0, 5 0 and 10 0 are considered. The nominal impingement point of the oblique shock wave with a flow deflection angle of 12 0 is fixed at the onset of the expansion corner, and flow conditions are kept the same for all cases. The numerical results are in good agreement with previous experimental and numerical data. Various flow phenomena, including the flow separation, the post-shock turbulent boundary layer and the flow unsteadiness in the interaction region, have been systematically studied. Analysis of the instantaneous and mean flow fields indicates that the main effect of the expansion corner is to significantly decrease the size and three-dimensionality of the separation bubble. A modified scaling analysis is proposed for the expansion effect on the interaction length scale, and a satisfactory result is obtained. Distributions of the mean velocity, the Reynolds shear stress and the turbulent kinetic energy show that the post-shock turbulent boundary layer in the downstream region experiences a faster recovery to the equilibrium state as the expansion angle is increased. The flow unsteadiness is studied using spectral analysis and dynamic mode decomposition, and dynamically relevant modes associated with flow structures originated from the incoming turbulent boundary layer are clearly identified. At large expansion angle (α=10 0 ), the unsteadiness of the separated shock is dominated by medium frequencies motions, and no low frequency unsteadiness is observed. The present study confirms that the driving mechanism of the low frequency unsteadiness is strongly related to the separated shock and the detached shear layer.