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Low Speed Streaks Instability of Direct Numerical Simulation of Turbulent Boundary Layer Flows with Adverse Pressure Gradient

type de publication      communication internationale avec actes publiés
date de publication 2011
auteur(s) Laval Jean-Philippe; Marquillie Matthieu; Ehrenstein Uwe
  
conférence Seventh International Symposium on Turbulence and Shear Flow Phenomena (TSFP7)
     dates de 28-07-2011 à 31-07-2011
     lieu Ottawa, Canada
     nom des actes Proceedings of the Seventh International Symposium on Turbulence and Shear Flow Phenomena
  
pages 1 – 5
résumé A direct numerical simulation (DNS) of a turbulent channel flow with a lower curved wall is performed at Reynolds number Reτ 600 at inlet. Low-speed streak structures are extracted from the turbulent flow field and base flows formed with conditional streaks averages, superimposing the mean streamwise velocity profile, are used for linear stability analyzes. The instability in the presence of a strong pressure gradient at the lower wall is shown to be of varicose type, whereas at the upper wall (with weak pressure gradient) varicose and sinuous unstable modes can coexist. The onset of the dominant instability mechanism of varicose type is shown to coincide with the strong production peaks of turbulent kinetic energy near the maximum of pressure gradient on both the curved and the flat walls. The size and shape of the counter-rotating streamwise vortices associated with the instability modes are shown to be reminiscent of the coherent vortices emerging from the streak skeletons in the direct numerical simulation.
mots clés direct numerical simulation, coherent structure, instability
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