Flow over an airfoil

Objective :

To simulate the flow over a NACA0017 airfoil and for the angle of attacks 0,2,4,6,8,10 compare the lift and drag forces

About airfoil :

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 flight 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. Most foil shapes require a positive angle of attack to generate lift, but cambered airfoils can generate lift at zero angle of attack. This "turning" of the air in the vicinity of the airfoil creates curved streamlines, resulting in lower pressure on one side and higher pressure on the other. This pressure difference is accompanied by a velocity difference, via Bernoulli's principle, so the resulting flowfield about the airfoil has a higher average velocity on the upper surface than on the lower surface. The lift force can be related directly to the average top/bottom velocity difference without computing the pressure by using the concept of circulation and the Kutta–Joukowski theorem.

Modelling :

For the NAAC0017 airfoil, we get the data from

http://airfoiltools.com/airfoil/naca4digit?MNaca4DigitForm%5Bcamber%5D=0&MNaca4DigitForm%5Bposition%5D=0&MNaca4DigitForm%5Bthick%5D=17&MNaca4DigitForm%5BnumPoints%5D=81&MNaca4DigitForm%5BcosSpace%5D=0&MNaca4DigitForm%5BcosSpace%5D=1&MNaca4DigitForm%5BcloseTe%5D=0&yt0=Plot

In this data there is absence of z coordinate therefore, we edit the data file and put the value of z-coordinate as zeros so that Solidworks reads the data and forms the spline so we use this entity to generate the sketch and build a 3D model of the airfoil

Flow simulation :

1. Create a wizard in flow simulation
2. set the flow as external flow and give the time dependence input according to the length of the computational domain we plan to put
3. Set the input velocity in the x-direction as 600 m/s
4. As default computational domain is very short to simulate the results therefore we vary the computational domain to have more accurate results
5. also, we use the 2D domain so that it consumes the less time
6. now we put the global mesh size to a higher number and local mesh to the surface of the airfoil which will increase the accuracy of the result
7. Now we put the goals as the surface goal for force in x and y-direction
8. set the results for the cut plot of velocity and pressure and put the goal plot
9. Run the simulation for different conditions of the angle of attack

Results :

The pressure at the angle of attack

• 0

• 2

• 4

• 6

• 8

• 10

Velocity at the angle at attack

• 0

• 2

• 4

• 6

• 8

• 10

force in x and y-direction at an angle of attack

• 0 :

Goal Name	Unit	Value	Averaged Value	Minimum Value	Maximum Value	Progress [%]	Use In Convergence	Delta	Criteria
SG Force (X) 1	[N]	6.9560856	6.946572942	6.908279157	6.975717245	100	Yes	0.003951669	0.172527647
SG Force (Y) 2	[N]	0.092047524	0.075262395	-0.013152077	0.163838812	31	Yes	0.011221851	0.003481858

• 2

Goal Name	Unit	Value	Averaged Value	Minimum Value	Maximum Value	Progress [%]	Use In Convergence	Delta	Criteria
SG Force (X) 1	[N]	7.022655147	7.025101383	6.985715036	7.05926994	100	Yes	0.005091747	0.172999722
SG Force (Y) 2	[N]	-3.226904944	-3.236133032	-3.323680172	-3.148556802	100	Yes	0.010178817	0.072240429

• 4

Goal Name	Unit	Value	Averaged Value	Minimum Value	Maximum Value	Progress [%]	Use In Convergence	Delta	Criteria
SG Force (X) 1	[N]	7.351604745	7.383659962	7.34870619	7.418156832	100	Yes	0.005080714	0.180264358
SG Force (Y) 2	[N]	-6.73234737	-6.729352434	-6.783888128	-6.680614295	100	Yes	0.011620683	0.135433101

• 6

Goal Name	Unit	Value	Averaged Value	Minimum Value	Maximum Value	Progress [%]	Use In Convergence	Delta	Criteria
SG Force (X) 1	[N]	7.836343818	7.867316112	7.814909774	7.927209945	100	Yes	0.013495645	0.189396468
SG Force (Y) 2	[N]	-9.989185218	-10.06551739	-10.13137451	-9.969313155	100	Yes	0.121672388	0.198893105

• 8

Goal Name	Unit	Value	Averaged Value	Minimum Value	Maximum Value	Progress [%]	Use In Convergence	Delta	Criteria
SG Force (X) 1	[N]	8.634287962	8.63337656	8.578485666	8.706215902	100	Yes	0.019625098	0.204748518
SG Force (Y) 2	[N]	-13.38322771	-13.38478121	-13.48057972	-13.26515157	100	Yes	0.052691728	0.256882475

• 10

Goal Name	Unit	Value	Averaged Value	Minimum Value	Maximum Value	Progress [%]	Use In Convergence	Delta	Criteria
SG Force (X) 1	[N]	9.523739147	9.50844663	9.45509981	9.559490007	100	Yes	0.005932437	0.224167979
SG Force (Y) 2	[N]	-16.61366511	-16.57666144	-16.66660321	-16.50420836	100	Yes	0.162394845	0.315963808

Conclusion :

From the cpmparision graph we can say that with respect to angle of attack drag force is increasing slowly showing parabolical pathway and lift force increses linearly