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

2. 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

3. 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

4. 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

5. 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

6. 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