Large Eddy Simulations of an Airfoil in Turbulent Inflow Lasse Gilling, lg@civil.aau.dk Department of Civil Engineering, Aalborg University, Denmark Extended visit at Chalmers, Sweden

Numerical Setup The flow past a NACA 0015 airfoil is studied Turbulence intensity (TI) and angle of attack (AOA) is varied The EllipSys3D flow solver is used Wall boundary layer is modeled by detached eddy simulation The k-ω SST turbulence model is used Symmetry BC c Inlet BC Flow dir. AOA 3c Outlet BC ~4c Symmetry BC

Results: Lift and Drag Flow sensitive to turbulence 1.5 2D RANS LES, TI=0.0 % 0.3 LES, TI=0.5 % LES, TI=2.0 % 0.25 Measurements 1 0.2 D C L C 0.15 0.5 2D RANS 0.1 LES, TI=0.0 % LES, TI=0.5 % 0.05 LES, TI=2.0 % Measurements 2 4 6 8 10 12 14 16 18 20 2 4 6 8 10 12 14 16 18 20 Angle of attack [deg] Angle of attack [deg] Flow sensitive to turbulence LES with no inflow turbulence predicts stall too late LES with 0.5 % TI gives good agreement before stall LES with 2.0 % TI gives poor results for low AOA but better after stall 2D RANS is good for low AOA, but fails to predict stall

Results: Surface Pressure Good agreement in general Flow very sensitive at 16° AOA 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 -1 2 3 4 5 6 7 x/c -c p AOA=14 deg LES, TI=0.0 % LES, TI=0.5 % LES, TI=2.0 % Measurements 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 -1 2 3 4 5 6 7 x/c -c p AOA=16 deg LES, TI=0.0 % LES, TI=0.5 % LES, TI=2.0 % Measurements 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 -1 2 3 4 5 6 7 x/c -c p AOA=18 deg LES, TI=0.0 % LES, TI=0.5 % LES, TI=2.0 % Measurements

Flow Visualization AOA=16° and TI=0.1 % 20 40 60 80 100 120 140 160 180 1 1.1 1.2 1.3 1.4 1.5 a b c d e f g h i tU/c C L TI=0.1 % AOA=16° and TI=0.1 % Low separation gives high lift and vice versa Large variations in spanwise direction and time

Future Plans Implement a momentum disc approach of imposing the inflow turbulence Save mesh points upstream of the airfoil Reduce computational costs Investigate influence of turbulence length scale