Analysis of adverse pressure gradient effects in the boundary layer of a NACA0012 airfoil at high angles of attack

Abstract

The characteristics of a turbulent boundary layer (TBL) subjected to an adverse pressure gradient (APG) are analyzed by a wall-resolved large eddy simulation (LES). The LES is performed for a NACA0012 airfoil at 9 deg. angle of attack, Reynolds number Re = 400, 000 and Mach number M = 0.2. Results are first presented in terms of aerodynamic coefficients and integral quantities. Then, turbulence statistics are analyzed for different chord positions to allow an assessement of different APGs on the Reynolds stresses and turbulent kinetic energy (TKE) budgets. The APGs are shown to impact the turbulence statistics, especially the Reynolds stress distributions and, subsequently, the production, dissipation and pressure diffusion terms of the TKE budgets. A secondary peak emerges for the tangential Reynolds stress as the APG increases. Moreover, all the other stress components increase with the APG. This leads to a production plateau on the outer-layer, which is counterbalanced by higher turbulence dissipation values away from the wall. An increasing APG also leads to a higher dissipation near the wall, which becomes balanced by higher viscous and pressure diffusion components of the budget.