Flow over an airfoil

1. OBJECTIVES

In this Project, CFD analysis of the two-dimensional subsonic flow over a NACA 0017 airfoil at various angles of attack and compare the lift and drag force. The geometry of the airfoil is created using SOLIDWORKS. CFD analysis is carried out using Flow Simulation Wizard at various angles of attack from 0° to 10° with an interval of 2°. Velocity distributions over NACA-0017 airfoil for different angles of attack are presented. Drag Force and Lift Force are plotted and compared.

2. THEORY

Airfoil is defined as the cross-section of a body that is placed in an airstream in order to generate useful aerodynamic force.

Computational Fluid Dynamics (CFD) has fascinated researchers, as it is a fast, accurate and reliable method of analyzing the variation of hydrodynamic properties of the flow over and within a body. Computational Fluid Dynamics (CFD) is a branch of fluid mechanics that uses numerical methods and algorithms to solve complex problems involving fluid flow.

Angle of attack is the angle between the oncoming air or relative wind and a reference line on the airplane or wing. Sometimes, the reference line is a line connecting the leading edge and trailing edge at some average point on the wing.

Effect of angle of attack:

• Increases as the angle of attack increase the lift force increase proportionately. And a certain point, called critical angle of attack, upper surface flow is more separated and the airfoil or wing is producing its maximum coefficient of lift.
• The study of airfoil behavior to varying angle of attacks is made in order to determine the best possible dimensions for practical conditions. In most airplanes, this is about 16 to 18 degrees. During a cruise, the requirement is to maintain the angle of attack where the total drag on the airplane is minimum so as to use the minimum thrust and therefore, minimum fuel consumption. This could occur at an angle of about 3 to 5 degrees.

NACA-0017 data taken from below link

Click here for the NACA-0017 data

The present study aims to analyze the flow field for NACA-0017 airfoil at various angles of attack and also to compare the lift and drag force.

3. GEOMETRY AND MESH GENERATION

i. Initial Airfoil geometry

ii. Extruded Part

iii. Mesh Generated

4. INPUTS AND BOUNDARY CONDITIONS

The problem consists of flow around an airfoil at various angles of attack (0, 2, 4, 6, 8, 10 degrees). The inputs and boundary conditions are presented in Table 1.

Inputs and boundary conditions

Also,

• Surface roughness = 0
• Gravity -not considered

5. PROCEDURE

1. An airfoil is created by using convert entities then line command.
2. For the different angle of attacks rotate entities is used.
3. The airfoil is extruded to 0.5 mm. Now save the file.
4. The flow simulation is created using the wizard menu.
5. The analysis type is selected as external. Time-dependent is selected.
6. Total analysis time is selected as 5 sec and output time is 1sec.
7. The fluid is selected as air and velocity parameter over X-direction is selected as 600m/s and then click finish.
8. Now a computational domain is created by using the 2D option.
9. The computational domain is expanded along both y-directions and x-direction in such a way that the length after the wake region should be 5 times the length ahead of wake region.
10. The Global mesh is defined and the local mesh is defined by selecting the surface. It is refined up to a level of 3.Local mesh is inserted around the surface of airfoil for better simulation.
11. The goals option is selected then force x and force y selected after selecting the surface.
12. Run the simulation.
13. Now a cut plot is made along x-direction and velocity over the airfoil is selected.
14. Color refining is given 15.
15. Goal plots are plotted for drag force(force x) and lift(force y) .
16. The above procedure is followed for different attack angles and the following results are used to plot the necessary graphs.

5. RESULTS

Results are computed and studied on different angle of attacks.

Here,

• Integrated force along the x-axis is Drag force.
• Integrated force along the y-axis is Lift force.

Case 1: Angle of attack at 0°

• Cut Plot: Velocity Contour

• Drag force and Lift force

1. Drag Force: 802.814 N
2. Lift Force: -0.494 N

Graph:

i. Drag Force ii. Lift Force

Case 2: Angle of attack 2°

Cut Plot: Velocity Contour

Drag force and Lift force

i. Drag Force: 837.770 N

ii. Lift Force: 2062.072 N

Graph:

i. Drag Force ii. Lift Force

Case 3: Angle of attack 4°

Cut Plot: Velocity Contour

Drag force and Lift force

i. Drag Force: 1041.878 N

ii. Lift Force: 4108.176 N

Graph:

i. Drag Force ii. Lift Force

Case 4: Angle of attack 6°

Cut Plot: Velocity Contour

Drag force and Lift force

i. Drag Force: 1403.018 N

ii. Lift Force: 6116.934 N

Graph:

i. Drag Force ii. Lift Force

Case 5: Angle of attack 8°

Cut Plot: Velocity Contour

Drag force and Lift force

i. Drag Force: 1910.446 N

ii. Lift Force: 8103.75 N

Graph:

i. Drag Force ii. Lift Force

Case 6: Angle of attack 10°

Cut Plot: Velocity Contour

Drag force and Lift force

i. Drag Force: 2511.039 N

ii. Lift Force: 10042.548 N

Graph:

i. Drag Force ii. Lift Force

Calculated Drag Force And Lift Force of all the angle of attack

Comparison study

Angle of attack	Average Drag Force (N)	Average Lift Force(N)
0°	802.814	-0.494
2°	837.770	2062.072
4°	1041.878	4108.176
6°	1403.018	6116.934
8°	1910.446	8103.75
10°	2511.039	10042.548

Graph:

• Drag Force vs Angle of attack

• Lift Force vs Angle of attack

• Comparing Drag force vs Lift Force:

To compare the characteristics of the drag and lift force the following graph is prepared.

6. CONCLUSION

With the help of SOLIDWORKS Flow Simulation, successful analysis of the NACA-0017 airfoil has been carried at various angles of attack (0, 2, 4, 6, 8, 10 degrees) and following observation has been made.

• With the increase in angle of attack, the number of iterations required to give the result get reduced.
• With the increase in angle of attack, Drag force increases slowly and lift force increases rapidly.
• With the increase in angle of attack, the velocity of air over the airfoil increased

Google Drive Link - https://drive.google.com/drive/folders/1MBCzrcQ04bV6l3usqw-71sEGTdvrbXUQ?usp=sharing