Flow over an airfoil using Solidworks

Objective- Flow over an airfoil for the angle of attacks 0,2,4,6,8,10 & compare the lift and drag forces.

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.

Input	Value
Units	SI units
Time Dependent	Total analysis time: 5s
	Output Time step: 1s
Analysis Type	External Flow
Fluids	Air
Density	1.225 kg/m³
Inlet velocity	600m/s

Theory-

Introduction- An Airfoil is defined as the cross-section of a body that is placed in an airstream in order to generate useful aerodynamic force. An airfoil or aerofoil is the cross-sectional shape of a wing, blade (of a propeller, rotor, or turbine), or sail (as seen in cross-section).

Angle of attack- 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.

Procedure steps:

1.Insert>Curves>Curves trough reference point) and convert entities in front plane & then using line command complete sketch.
2. Rotate the airfoil as per the needed angle of attack (0/2/4/6/8/10).
3. Extrude the curve after converting the curve into a sketch to 0.2m.
4. The flow simulation is created using the wizard menu.
5. Select wizard and input respective details including medium as per parameters given above to set the project.
6. The analysis type is selected as external.
7. Time-dependent is selected. Total analysis time is selected as 5 sec and output time is 1sec.
8. The fluid is selected as air and velocity parameter over X-direction is selected as 600m/s and then click finish.
9. Now a computational domain is created by using the 2D option.
10. 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.
11. The Global mesh is defined and the local mesh is defined by selecting the surface. It is refined up to a level of 3.
12. The goals option is selected then force x and force y selected after selecting the surface.
13. Run the simulation.
14. Now two cut plots are made along x-direction and pressure & velocity over the airfoil is selected.Color refining is given 200.
15. A goal plot is plotted between drag force along the x-direction and lift along the y-axis.
16. The above procedure is followed for different attack angles and the following results are used to plot the necessary graphs.

Results- Results are computed and studied on different angle of attacks. Let's run one by one on the different angle of attacks.
Here,
SG Force (X)1 denotes Surface Goal force at X axis which is called as Drag Force.
SG Force (Y)1 denotes Surface Goal Force at Y axis which is called as Lift Force.

• Case 1: Angle of attack = 0 deg
• A) Pressure contour

• B) Velocity contour

C) Goal plot for Drag Force

D) Goal plot for Lift Force

E) Table for 0 degree Angle of Attack

Goal Name	Unit	Value	Averaged Value	Minimum Value	Maximum Value	Progress [%]	Use In Convergence	Delta	Criteria
Drag Force	[N]	302.0572355	302.0642017	302.0067197	302.1288315	100	Yes	0.122111819	5.738446647
Lift Force	[N]	1.432460771	1.291764283	0.891763903	1.547873723	100	Yes	0.199776935	0.262190195

• Case 2: Angle of attack = 2 deg
• A) Pressure contour

B) Velocity contour

C) Goal plot for Drag Force

D) Goal plot for Lift Force

E) Table for 2 degree Angle of Attack

Goal Name	Unit	Value	Averaged Value	Minimum Value	Maximum Value	Progress [%]	Use In Convergence	Delta	Criteria
SG Force (X) 1	[N]	332.896	332.954	332.752	333.115	100	Yes	0.363	6.267
SG Force (Y) 1	[N]	833.795	833.278	832.234	834.166	100	Yes	1.931	6.646

• Case 3: Angle of attack = 4 deg
• A) Pressure contour

B) Velocity contour

C) Goal plot for Drag Force

D) Goal plot for Lift Force

E) Table for 4 degree Angle of Attack

Goal Name	Unit	Value	Averaged Value	Minimum Value	Maximum Value	Progress [%]	Use In Convergence	Delta	Criteria
SG Force (X) 1	[N]	413.441	413.531	413.381	413.691	100	Yes	0.31	7.634
SG Force (Y) 1	[N]	1640.576	1635.409	1628.029	1640.576	100	Yes	12.546	16.4

• Case 4: Angle of attack = 6 deg
• A) Pressure contour

B) Velocity contour

C) Goal plot for Drag Force

D) Goal plot for Lift Force

E) Table for 6 degree Angle of Attack

Goal Name	Unit	Value	Averaged Value	Minimum Value	Maximum Value	Progress [%]	Use In Convergence	Delta	Criteria
SG Force (X) 1	[N]	552.675	552.887	552.623	553.316	100	Yes	0.693	10.112
SG Force (Y) 1	[N]	2442.035	2440.176	2433.25	2443.902	100	Yes	10.652	28.724

• Case 5: Angle of attack = 8 deg
• A) Pressure contour

1. B) Velocity contour

C) Goal plot for Drag Force

D) Goal plot for Lift Force

E) Table for 8 degree Angle of Attack

Goal Name	Unit	Value	Averaged Value	Minimum Value	Maximum Value	Progress [%]	Use In Convergence	Delta	Criteria
SG Force (X) 1	[N]	756.362	756.334	755.575	757.383	100	Yes	0.331	13.882
SG Force (Y) 1	[N]	3250.725	3249.883	3246.644	3252.17	100	Yes	0.81	43.879

• Case 6: Angle of attack = 10 deg
• A) Pressure contour

B) Velocity contour

C) Goal plot for Drag Force

D) Goal plot for Lift Force

E) Table for 10 degree Angle of Attack

Goal Name	Unit	Value	Averaged Value	Minimum Value	Maximum Value	Progress [%]	Use In Convergence	Delta	Criteria
SG Force (X) 1	[N]	996.038	995.723	994.203	996.709	100	Yes	0.148	18.327
SG Force (Y) 1	[N]	4034.082	4033.199	4027.911	4037.246	100	Yes	0.746	60.955

Comparisons

• Averaged Drag Force vs Angle of Attack

• Averaged Lift Force vs Angle of Attack

Conclusions

1. We can see that the pressure region below the airfoil turns to light blue as the angle of attack increases. This indicates increase in pressure below aerofoil as angle of attack increases.The pressure region above the airfoil turns to dark blue as the angle of attack increases. This indicates decrease in pressure above aerofoil as angle of attack increases.
2. So ineffect the pressure difference between above and below airfoil is increasing as angle of attch increases.This is the reason for the increase in lift force.
3. 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.
4. The increase in lift force with increase in angle of attack is almost linear while that of drag is nonlinear. Similary same effect can also be seen in velocity contour. When more air flows through the upper region of airfoil compared to lower region, velocity will be more in this upper region and pressure will drop in this area. This will create a suction which causes the lift force.
5. We can see the increase in the size of the wake region as the angle of attack increases.