Bifurcation scenario for a two-dimensional static airfoil exhibiting trailing edge stall

نویسندگان

چکیده

We numerically investigate stalling flow around a static airfoil at high Reynolds numbers using the Reynolds-averaged Navier–Stokes equations (RANS) closed with Spalart–Allmaras turbulence model. An arclength continuation method allows to identify three branches of steady solutions, which form characteristic inverted S-shaped curve as angle attack is varied. Global stability analyses these solutions reveal existence two unstable modes: low-frequency mode, for angles in stall region, and high-frequency vortex shedding larger attack. The mode bifurcates several times along solutions: there are Hopf bifurcations, two-fold degenerate eigenvalue saddle-node bifurcations. This induces cyclic separation reattachment airfoil. Unsteady simulations RANS confirm large-amplitude periodic that oscillate phase space. analysis space shows that, when decreasing attack, solution collides middle-branch thus disappears via homoclinic bifurcation orbits. Finally, one-equation nonlinear model introduced disappearance limit cycle, increasing due

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ژورنال

عنوان ژورنال: Journal of Fluid Mechanics

سال: 2021

ISSN: ['0022-1120', '1469-7645']

DOI: https://doi.org/10.1017/jfm.2021.767