Flow over an airfoil

Aim:

To perform an external flow simulation on a NACA0017 airfoil and compare the drag and lift force for every angle of attack at 0,2,4,6,8,10 deg.

OBJECTIVES

To compare the lift force and drag force of an airfoil for different angle of attacks.

THEORY

The NACA airfoils are airfoils shapes of an aircraft wings developed by National Advisory Committee for Aeronautics. The shapes of an airfoil are described by a series of digit followed by the word NACA. There are different types of series of NACA airfoil. In this project, four-digit series is used. The first digit describes maximum camber as a percentage of chord. The second digit describes the distance of maximum camber from airfoil leading edge intents of chord. The last two digits gives the maximum thickness of the airfoil as percent of chord.

PROCEDURE

• The co-ordinates for NACA0017 is imported to Soildworks using Insert curve option. MKS unit system is used in this process.
• Suitable plane is selected and Convert Entities is used to for further sketching. The tail end of the curve is closed using the line command to make it has a closed sketch.
• The curve can be rotated using the Rotate entities command. Select the entities to rotate and specify the centre of rotation along with the degree to which the entities must rotate. This procedure can be used to rotate the curve for different degrees.
• Extrude the surface to certain width and save the drawing.

The following are the 3D model of airfoil for various degree of angle of attack

0-degree Angle of Attack

2-degree Angle of Attack

4-degree Angle of Attack

6-degree Angle of Attack

8-degree Angle of Attack

10-degree Angle of Attack

FLOW STIMULATION SETUP

• Flow stimulation can be enabled by selecting Soildworks Add-Ins.
• Click on the Wizard icon to create a new project.
• Specify the project name and click Next.
• In Analysis type select External Flow.
• Click on time dependent stimulation. Stimulation time of 5 seconds and Time of step as 1 second and click Next.
• In Initial wall conditions specify the velocity in the X-direction as 600 and click Finish.
• In Computational domain select 2D stimulation and XY Plane.
• The inlet boundary should be 5 times the chord length from the leading edge and the distance between the trailing edge and outlet boundary should be 10-15 times the chord length.
• Specify the Global goals and Surface Goals by right clicking on Goals and select force as an input parameter.
• Click on global mesh and specify the initial level of mesh. Create a local mesh around the top surface of the airfoil for a better refinement.
• Run the stimulation.

The following are the results obtained for various degrees of angle of attacks.

0-degree Angle of attack

Velocity Profile

Pressure profile

Lift force and Drag force

2-degree Angle of attack

Pressure profile

Lift force and Drag force

4-degree Angle of attack

Velocity profile

Pressure profile

Lift force and Drag force

6-degree Angle of attack

Velocity profile

Pressure profile

Lift force and Drag force

8-degree Angle of attack

Velocity Profile

Pressure profile

Lift force and Drag force

10-degree Angle of attack

Velocity profile

Pressure profile

Lift force and Drag force

The relationship between angle of attack and lift force and drag force is shown below

Angle of Attack (degree)	Drag force (N)	Lift force (N)
0	151.898	0.846
2	167.064	412.379
4	208.039	822.001
6	278.996	1235.839
8	379.346	1629.392
10	507.478	2036.098

Conclusion

• At zero degree angle of attack the lift is found to be zero due to symmetry of airfoil.
• Also there is symmetry found in velocity and pressure plot at 0 deg angle of attack.
• As the angle of attack increses the lift force also increases and the size of wake region al so increases.
• The blue light increses below the airfoil in the pressure plot as angle of attack is increased as pressure increases in that region.
• Similarly as the velocity flows over the airfoil more than the lower region the pressure under it decreases this creates suction and causes lift.