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Large-eddy simulation of laminar transonic buffet.
- Source :
- Journal of Fluid Mechanics; 9/10/2018, Vol. 850, p156-178, 23p, 2 Color Photographs, 2 Black and White Photographs, 16 Graphs
- Publication Year :
- 2018
-
Abstract
- A large-eddy simulation of laminar transonic buffet on an airfoil at a Mach number M = 0.735, an angle of attack α = D 4°, a Reynolds number Re<subscript>c</subscript> = 3 × 10<superscript>6</superscript> has been carried out. The boundary layer is laminar up to the shock foot and laminar/turbulent transition occurs in the separation bubble at the shock foot. Contrary to the turbulent case for which wall pressure spectra are characterised by well-marked peaks at low frequencies (St = f ּּ· c/U<subscript>∞</subscript> ≃ 0.06–0.07, where St is the Strouhal number, f the shock oscillation frequency, c the chord length and U<subscript>∞</subscript> the free-stream velocity), in the laminar case, there are also well-marked peaks but at a much higher frequency (St = 1.2). The shock oscillation amplitude is also lower: 6% of chord and limited to the shock foot area in the laminar case instead of 20% with a whole shock oscillation and intermittent boundary layer separation and reattachment in the turbulent case. The analysis of the phase-averaged fields allowed linking of the frequency of the laminar transonic buffet to a separation bubble breathing phenomenon associated with a vortex shedding mechanism. These vortices are convected at U<subscript>c</subscript>/U<subscript>∞</subscript> ≃ 0.4 (where U<subscript>c</subscript> is the convection velocity). The main finding of the present paper is that the higher frequency of the shock oscillation in the laminar regime is due to a different mechanism than in the turbulent one: laminar transonic buffet is due to a separation bubble breathing phenomenon occurring at the shock foot. [ABSTRACT FROM AUTHOR]
Details
- Language :
- English
- ISSN :
- 00221120
- Volume :
- 850
- Database :
- Complementary Index
- Journal :
- Journal of Fluid Mechanics
- Publication Type :
- Academic Journal
- Accession number :
- 130981140
- Full Text :
- https://doi.org/10.1017/jfm.2018.470