Flow over an airfoil
FLOW SIMULATION OVER A NACA AIRFOIL
AIM – Run a flow simulation over NACA airfoil with angle of attack 0,2,4,6,8,10.
OBJECTIVES-
1. Create a 3D airfoil after importing data from airfoil database.
2. Run flow simulation with angle of attack 0,2,4,6,8,10.
3. Compare velocity cut plot for all cases.
INTRODUCTION-
An airfoil is the cross-sectional shape of a wing, blade (of a propeller, rotor, or turbine), or sail (as seen in cross-section).
An airfoil-shaped body moving through a fluid produces an aerodynamic force. The component of this force perpendicular to the direction of motion is called lift. The component parallel to the direction of motion is called drag. Subsonic flights airfoils have a characteristic shape with a rounded leading edge, followed by a sharp trailing edge, often with a symmetric curvature of upper and lower surfaces. Foils of similar function designed with water as the working fluid are called hydrofoils.
The lift on an airfoil is primarily the result of its angle of attack. When oriented at a suitable angle, the airfoil deflects the oncoming air (for fixed-wing aircraft, a downward force), resulting in a force on the airfoil in the direction opposite to the deflection. This force is known as aerodynamic force and can be resolved into two components: lift and drag.
NACA 0017 air
PROCEDURE-
1. Download data for NACA0017 airfoil from airfoil database and save it as text document.
2. Click on New> Part. Click on Insert> Curves> Curves through XYZ points.
3. Click on Front plane. Select Convert entities. Select Curve.
4. Draw a line to close the trailing edge. Extrude the curve to .200m.
5. Click on drop down button in Move entities. Select Rotate entities. Set angle to 0°. Save the part.
6. Click on Wizard in Flow Simulation. Select flow type external. Use SI units.
7. In Physical features> Time-dependent. Put Total analysis time = 5 sec and Output time step = 1 sec.
8. Select Gases> Air. Click on Add. In Parameter definition, see Velocity parameters. Put velocity in X direction = 600 m/s
9. In result resolution drag slider to 5. Click on finish.
10. Set computational domain to 2D. Set size such that right edge of domain to 10 times of chord and left edge of domain to 4 times chord.
11. Set goal surface plot of force in X and Y direction.
12. Click on Results>Cut Plot and insert a cut plot parallel to front plane.
13. Click on Run. Wait for Solver to finish.
14. Export the result to spreadsheet.
15. Repeat the above steps for angles 2, 4, 6, 8, 10.
RESULTS-
Case 1 Angle of attack = 0°
Pressure:
Velocity:
Case 2 Angle of attack = 2°
Pressure:
Velocity:
Case 3 Angle of attack = 4°
Pressure:
Velocity:
Case 4 Angle of attack = 6°
Pressure:
Velocity:
Case 5 Angle of attack = 8°
Pressure:
Velocity:
Case 6 Angle of attack = 10°
Pressure:
Velocity:
Comparision of average force (both drag and lift) at different angle of attacks:
EXPLANATIONS & CONCLUSIONS:
1. Lift force increases with increase in angle of attack till it reaches a maximum value.
2. Drag force increases with increase in angle of attack as more surface gets in first contact with fluid.
3. Also, with this increase in angle of attack the airfoil separates and develops a pressure gradient at frontal area with higher pressure and dorsal area with lower pressure.
4. Rate of increase of lift force is greater than drag