Pressure gradient effects on coherent structures and anisotropy of a turbulent boundary layer over a NACA0012 airfoil at 12° angle of attack

Author(s)

Silva, Leandro J. ; Wolf, William R.

• Document type: Journal article
• Source: AIAA AVIATION FORUM AND ASCEND 2024; v. N/A, p. 9-pg., 2024-01-01.

Abstract

We investigate the turbulent boundary layer (TBL) over a NACA0012 airfoil at angle of attack 12 deg. A wall-resolved LES is performed for a chord based Reynolds number Re = 4 x 10(5) and freestream Mach number Re = 0.2 for which boundary layer tripping is applied near the leading edge. Mild, moderate and strong adverse pressure gradients (APGs) develop over the airfoil and, despite the strong APG, the mean flow remains attached. We observe a secondary peak in the Reynolds stress profiles arising in the outer layer and, for a strong APG, it overcomes the first peak observed in the inner layer. Due to the strong APGs on the suction side, the mean velocity profiles depict three inflexion points, the third being unstable under inviscid stability criteria. This promotes the formation of a shear layer in the outer region of the TBL which, in turn, leads to the occurrence of Kelvin-Helmholtz vortices captured by a spectral proper orthogonal decomposition (SPOD). The SPOD analysis also shows that streaks form along the airfoil suction side and, as the APG becomes stronger, they grow along the spanwise and wall-normal directions. (AU)

• FAPESP's process: 13/08293-7 - CCES - Center for Computational Engineering and Sciences
• Grantee: Munir Salomao Skaf
• Support Opportunities: Research Grants - Research, Innovation and Dissemination Centers - RIDC
• FAPESP's process: 22/00256-4 - Statistics of turbulent boundary layers developing under different pressure gradients
• Grantee: Leandro Júnio de Oliveira Silva
• Support Opportunities: Scholarships in Brazil - Master
• FAPESP's process: 21/06448-0 - High-fidelity numerical simulations applied in unsteady aerodynamics, turbulence and aeroacoustics
• Grantee: William Roberto Wolf
• Support Opportunities: Research Grants - Young Investigators Grants - Phase 2