Adverse-pressure-gradient effects on extreme events and intermittency in the turbulent boundary layer of a NACA0012 at 12° angle of attack

Author(s)

de O Silva, Leandro Juni ; Wolf, William R. ; Vinuesa, Ricardo

• Document type: Journal article
• Source: AIAA AVIATION FORUM AND ASCEND 2024; v. N/A, p. 13-pg., 2024-01-01.

Abstract

We investigate the effects of adverse pressure gradients (APGs) on extreme and intermittent events in the turbulent boundary layer (TBL) of a NACA0012 airfoil at 12 deg. angle of attack. A wall-resolved large-eddy simulation (LES) is performed for a Reynolds number Re = 4 x 10(5) and freestream Mach number M = 0.2. Boundary-layer tripping is enforced near the leading edge to produce bypass transition. Despite the high angle of attack, the mean flow remains attached throughout the airfoil suction side, although the adverse pressure gradient exhibits a steep rise towards the trailing edge. Results of a quadrant analysis for the Reynolds shear-stress distribution show that sweeps are predominant near the wall, while ejections dominate in the outer region. The former are the main contributor to the inner peak of turbulence production. Due to the strong APG, a secondary peak of production arises in the outer layer, and the combination of both sweeps and ejections contribute to such peak. A backflow characterization is performed, demonstrating that as the APG increases, the magnitude of the friction coefficient decreases, leading to a higher probability of such events near the trailing edge. (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
• FAPESP's process: 23/01657-5 - Study of adverse pressure gradient effects in turbulent boundary layers
• Grantee: Leandro Júnio de Oliveira Silva
• Support Opportunities: Scholarships abroad - Research Internship - Master's degree