Flow over an airfoil

AIM: Flow over an Airfoil.

Objectives of the Project:

1. To model the flow over a NACA0017 airfoil.
2. For the angle of attacks of 0,2,4,6,8 and 10, compare the lift and drag force.

Introduction:

The NACA airfoils are airfoil shapes for aircraft wings developed by the National Advisory Committee for Aeronautics (NACA). The shape of the NACA airfoils is described using a series of digits following the word "NACA"

The NACA four-digit wing sections define the profile by:

1. First digit describing maximum camber as percentage of the chord.
2. Second digit describing the distance of maximum camber from the airfoil leading edge in tenths of the chord.
3. Last two digits describing maximum thickness of the airfoil as percent of the chord.

For example, the NACA 2412 airfoil has a maximum camber of 2% located 40% (0.4 chords) from the leading edge with a maximum thickness of 12% of the chord.

The NACA 0015 airfoil is symmetrical, the 00 indicating that it has no camber. The 15 indicates that the airfoil has a 15% thickness to chord length ratio: it is 15% as thick as it is long.

Angle of attack(AOA or `α`): It is the angle between a reference line on a body (often the chord line of an airfoil) and the vector representing the relative motion between the body and the fluid through which it is moving. Angle of attack is the angle between the body's reference line and the oncoming flow.

Geometrical Model of an Airfoil:

Procedure:

1. A curve is created on a sketch plane by using the geometrical curve data points.
2. Then, an airfoil is created by using line command and then convert entities.
3. The airfoil is extruded to 0.2m and saved the file
4. The flow simulation is created using the wizard option menu.
5. Under wizard option, the type of flow analysis is selected as external flow. Also, time dependent is selected with total analysis time and output time as 5sec and 1sec respectively.
6. The fluid is selected as an air and the velocity in the x-direction is taken as 600 m/s.
7. A computational domain is created by using 2D option.
8. Now global goal and surface goal are selected and then force x and force y selected after selecting the surface face of an airfoil.
9. The global mesh and local mesh are defined by selecting the surface face of an airfoil with refined upto level 3.
10. Run the simulation.
11. Now, a cut plot is made in xy plane and the velocity is determined over an airfoil. Color refinement for velocity increased to 200.
12. A goal plot is plotted between drag force and lift force along x and y direction respectively.
13. The above procedure is followed for different angle of attack and the results obtained are used to compare drag and lift force.

Results:

Note: Integrated force along x-direction: Drag Force

Integrated force along y-direction: Lift Force

• Case1: For an Angle of Attack at 0 degree.

Result Window:

Velocity Countour:

Drag Force and Lift Force:

Avg Drag Force: 306.476 N

Avg Lift Force: 0.327 N

Graphs:

Drag Force: Lift Force:

• Case2: For an Angle of Attack at 2 degree.

Result Window:

Velocity Countour:

Drag Force and Lift Force:

Avg Drag Force: 337.050 N

Avg Lift Force: 836.047 N

Graphs:

Drag Force: Lift Force:

• Case3: For an Angle of Attack at 4 degree.

Result Window:

Velocity Contour:

Drag Force and Lift Force:

Avg Drag Force: 418.346 N

Avg Lift Force: 1645.816 N

Graphs:

Drag Force: Lift Force:

• Case4: For an Angle of Attack at 6 degree.

Result Window:

Velocity Countour:

Drag Force and Lift Force:

Avg Drag Force: 556.926 N

Avg Lift Force: 2451.510 N

Graphs:

Drag Force: Lift Force:

• Case5: For an Angle of Attack at 8 degree.

Result Window:

Velocity Countour:

Drag Force and Lift Force:

Avg Drag Force: 761.448 N

Avg Lift Force: 3236.772 N

Graphs:

Drag Force: Lift Force:

• Case6: For an Angle of Attack at 10 degree.

Result Window:

Velocity Countour:

Drag Force and Lift Force:

Avg Drag Force: 1004.016 N

Avg Lift Force: 4020.571 N

Graphs:

Drag Force: Lift Force:

Comparison Study Table:

Angle of Attack(Degrees)	Average Drag Force(N)	Average Lift Force(N)
0	306.476	0.327
2	337.050	836.047
4	418.163	1645.816
6	556.926	2451.510
8	761.448	3236.772
10	1004.016	4020.571

Graphs:

Drag Force:

Lift Force:

Comparison Between Drag Force and Lift Force:

Observations and Conclusion:

• Analysis of NACA airfoil has been successfully carried out at various angle of attack(0,2,4,6,8 and 10) and the obervations are made.
• With the increase in angle of attack, the number of iterations get reduced to give the required result.
• It is observed from the above plots, that with the increase in angle of attack drag force increases slowly whereas lift force increases rapidly.
• The velocity of air over an airfoil increased with increase in angle of attack.