Flow over an airfoil
AIM: To model the flow over a NACA0017 airfoil and compare the lift and drag forces for the angle of attacks of 0,2,4,6,8,10.
INTRODUCTION:
The NACA foils are the shapes of the aircraft wings . These are developed by the National Advisory Committee for Aeronautics (NACA). The shape of the NACA airfoils is specified using a series of digits following the word "NACA".
NACA AIRFOIL SPECIFICATION:
This NACA airfoil series is followed by 4 digits e.g. NACA 0013, which designate the camber, position of the maximum camber and thickness. EXAMPLE :-
If an airfoil number is NACA0017 ( Designated by -NACA MPXX)
then:
- M is the maximum camber divided by 100. In the example M=0 so the camber is 0 or 0% of the chord.
- P is the position of the maximum camber divided by 10. In the example P=0 so the maximum camber is at 0 or 0% of the chord.
- XX is the thickness divided by 100. In the example XX=17 so the thiickness is 0.17 or 17% of the chord.
PROCEDURE :
1. Download the NACA0017 file from Airfoil Database list .
2. Got to Insert option -> Select Curves -> Select curve through XYZ points.
3. Make the curve a close volume by making it a closed entity.
4. Rotate by providing subsequent angle of attacks of 0,2,4,6,8,10.
5. Extrude the shape upto 0.195m .
6. Save the file before moving to wizard tool.
7. Select wizard tool and enter the conditions like External Flow, air as flow medium, transient simulation, and provide velocity in X-axis as 600m/s.
8. Edit computational domain to XY plane and 2D Geometry only.
9. Change the domain length 5 times the chord length of the airfoil at entry and 10-15 times at the exit of the airfoil.
10. As the mesh is not body fitted mesh hence insert a local surface mesh to increase the refinement at the surface of the airfoil upto 3.
11. Set surface goal, select force at X and Y which indicates Drag and Lift force respectively.
12. Run the simulation and get the simultaneous results for each Angle of Attack.
13. Move towards Insert preview section and show goal plots like Force .
14. Edit cut plots on XY plane .Show Contours and select velocity and mesh .
15. For removing choppy looks , Increase number of color segments to 200 to get more clearer and refined results.
16. Follow the same procedure at different angle of attacks.
Fig.1 Refined Local Mesh
OUTPUT & RESULTS :
CASE 1:
At 0 angle of attack-
After running the simulation we get required results ;
1. PRESSURE PROFILE -
Fig.2 Pressure Profile
2. VELOCITY PROFILE
Fig.3 Velocity Profile
3. COMPARISON OF FORCES( DRAG AND LIFT )
Fig.4 Comparison Of both forces
SG Force (X) 1 depicts surface Goal force at X axis which is Drag Force.
SG Force (Y) 1 depicts surface Goal Force at Y axis which is Lift Force.
Average Drag Force = 1293.0592 N
Average Lift Force = 0.624 N
CASE 1:
At 2 deg angle of attack-
After running the simulation we get required results ;
1. PRESSURE PROFILE -
Fig.5 Pressure Profile
2. VELOCITY PROFILE
Fig.6 Velocity Profile
3. COMPARISON OF FORCES( DRAG AND LIFT )
Fig.7 Comparison Of both forces
Average Drag Force = 1298.300 N
Average Lift Force = 610.799 N
CASE 3:
At 4 degrees angle of attack-
After running the simulation we get required results ;
1. PRESSURE PROFILE -
Fig.8 Pressure Profile
2. VELOCITY PROFILE
Fig.9 Velocity Profile
3. COMPARISON OF FORCES( DRAG AND LIFT )
Fig.10 Comparison Of both forces
SG Force (X) 1 depicts surface Goal force at X axis which is Drag Force.
SG Force (Y) 1 depicts surface Goal Force at Y axis which is Lift Force.
Average Drag Force = 1361.174 N
Average Lift Force = 1244.141 N
CASE 4:
At 6 degrees angle of attack-
After running the simulation we get required results ;
1. PRESSURE PROFILE -
Fig.11 Pressure Profile
2. VELOCITY PROFILE
Fig.12 Velocity Profile
3. COMPARISON OF FORCES( DRAG AND LIFT )
Fig.13 Comparison Of both forces
SG Force (X) 1 depicts surface Goal force at X axis which is Drag Force.
SG Force (Y) 1 depicts surface Goal Force at Y axis which is Lift Force.
Average Drag Force = 1448.239 N
Average Lift Force = 1897.244 N
CASE 5:
At 8 degrees angle of attack-
After running the simulation we get required results ;
1. PRESSURE PROFILE -
Fig.14 Pressure Profile
2. VELOCITY PROFILE
Fig.15 Velocity Profile
3. COMPARISON OF FORCES( DRAG AND LIFT )
Fig.16 Comparison Of both forces
SG Force (X) 1 depicts surface Goal force at X axis which is Drag Force.
SG Force (Y) 1 depicts surface Goal Force at Y axis which is Lift Force.
Average Drag Force = 1587.69 N
Average Lift Force =2483.632 N
COMPARISON GRAPHS BETWEEN ANGLE OF ATTACK AND DRAG & LIFT FORCE :-
Fig.17 Lift Force vs AOA
Fig.18 Drag Force vs AOA
CONCLUSION:-
1) The angle of attack is directly proportional to Drag force and lift force .
2) Lift force is nearly equal to zero in case of zero degree angle of attack.
3) Symmetry in velocity and pressure profile is seen in the zero degree angle of attack.
4) Drop in pressure is observed as the angle of attack increases.
5) Refining the mesh is important to get accurate results.