Pressure-Gradient Turbulent Boundary Layers Developing Around a Wing Section

Pressure-Gradient Turbulent Boundary Layers Developing Around a Wing Section A direct numerical simulation database of the flow around a NACA4412 wing section at R e c = 400,000 and 5∘ angle of attack (Hosseini et al. Int. J. Heat Fluid Flow 61, 117–128, 2016), obtained with the spectral-element code Nek5000, is analyzed. The Clauser pressure-gradient parameter β ranges from ≃ 0 and 85 on the suction side, and from 0 to − 0.25 on the pressure side of the wing. The maximum R e 𝜃 and R e τ values are around 2,800 and 373 on the suction side, respectively, whereas on the pressure side these values are 818 and 346. Comparisons between the suction side with zero-pressure-gradient turbulent boundary layer data show larger values of the shape factor and a lower skin friction, both connected with the fact that the adverse pressure gradient present on the suction side of the wing increases the wall-normal convection. The adverse-pressure-gradient boundary layer also exhibits a more prominent wake region, the development of an outer peak in the Reynolds-stress tensor components, and increased production and dissipation across the boundary layer. All these effects are connected with the fact that the large-scale motions of the flow become relatively more intense due to the adverse pressure gradient, as apparent from spanwise premultiplied power-spectral density maps. The emergence of an outer spectral peak is observed at β values of around 4 for λ z ≃ 0.65δ 99, closer to the wall than the spectral outer peak observed in zero-pressure-gradient turbulent boundary layers at higher R e 𝜃 . The effect of the slight favorable pressure gradient present on the pressure side of the wing is opposite the one of the adverse pressure gradient, leading to less energetic outer-layer structures. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png "Flow, Turbulence and Combustion" Springer Journals

Pressure-Gradient Turbulent Boundary Layers Developing Around a Wing Section

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Publisher
Springer Netherlands
Copyright
Copyright © 2017 by The Author(s)
Subject
Engineering; Engineering Fluid Dynamics; Fluid- and Aerodynamics; Engineering Thermodynamics, Heat and Mass Transfer; Automotive Engineering
ISSN
1386-6184
eISSN
1573-1987
D.O.I.
10.1007/s10494-017-9840-z
Publisher site
See Article on Publisher Site

Abstract

A direct numerical simulation database of the flow around a NACA4412 wing section at R e c = 400,000 and 5∘ angle of attack (Hosseini et al. Int. J. Heat Fluid Flow 61, 117–128, 2016), obtained with the spectral-element code Nek5000, is analyzed. The Clauser pressure-gradient parameter β ranges from ≃ 0 and 85 on the suction side, and from 0 to − 0.25 on the pressure side of the wing. The maximum R e 𝜃 and R e τ values are around 2,800 and 373 on the suction side, respectively, whereas on the pressure side these values are 818 and 346. Comparisons between the suction side with zero-pressure-gradient turbulent boundary layer data show larger values of the shape factor and a lower skin friction, both connected with the fact that the adverse pressure gradient present on the suction side of the wing increases the wall-normal convection. The adverse-pressure-gradient boundary layer also exhibits a more prominent wake region, the development of an outer peak in the Reynolds-stress tensor components, and increased production and dissipation across the boundary layer. All these effects are connected with the fact that the large-scale motions of the flow become relatively more intense due to the adverse pressure gradient, as apparent from spanwise premultiplied power-spectral density maps. The emergence of an outer spectral peak is observed at β values of around 4 for λ z ≃ 0.65δ 99, closer to the wall than the spectral outer peak observed in zero-pressure-gradient turbulent boundary layers at higher R e 𝜃 . The effect of the slight favorable pressure gradient present on the pressure side of the wing is opposite the one of the adverse pressure gradient, leading to less energetic outer-layer structures.

Journal

"Flow, Turbulence and Combustion"Springer Journals

Published: Aug 12, 2017

References

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