Flow over an airfoil

AIM: To Model the flow over a NACA0017 airfoil.

OBJECTIVE:

• To perform a flow stimulation over NACA0017 airfoil for various angle of attacks 0,2,4,6,8,10.
• To compare the lift and drag forces.

THEORY:

• Airfoil: Airfoil or Aerofoil is an aerodynamic shape which offers the best possible lift for the least amount of drag.They are primarily used for Aircraft wings, horizontal and vertical tail and the whole fuselage itself in a way is an airfoil shape. Apart from that you can see it for fan blades, compressor blades etc.

• NACA airfoil :NACA stands for National Advisory Committee for Aeronautics. This organization existed from 1915 to 1958, at which point its work was transferred to the newly formed NASA (National Aeronautics and Space Administration).NACA did a tremendous amount of work in developing our understanding of the behaviour of airfoils. They developed several series of standard airfoil shape families and tested them in wind tunnels. They started off with the “four-digit” family. These airfoils had a designation of something like NACA 2412.The last two digits give the thickness of the airfoil as a percentage of its chord. So that airfoil had a thickness that was 12% of its chord.The first digit of the four gives the height of the camber line at its highest point, also as a percentage of the chord. The second digit indicates where along the chord that maximum camber occurs. This time it’s in tenths of the chord. So the NACA 2412 has 2% camber occurring at 40% of the chord behind the leading edge and has a maximum thickness that is 12% of the chord. Here is a diagram showing it:

The red line is the camber line. That is the average between the upper and lower surfaces. The purple line shows what the upper surface would look like if there were no camber and the airfoil were symmetric top and bottom. That is, it is the upper surface of a NACA 2400 airfoil.

• Angle of attack: Angle of attack is the angle at which the oncoming air meets the wing.

In general, the greater the angle of attack, the more lift is generated by the wing. However, this is only true to a point. At some point the wing reaches its critical angle of attack,and at higher angles of attack the amount of lift generated drops dramatically. This is because the flow of air separates from the wing, forming turbulent eddies that destroy the ability of the wing to generate lift:

Beyond the critical angle of attack is the stalled region, where the wing is no longer effectively generating lift and the airplane is stalled.

PROCEDURE:

• Firstly we will copy the data file for NACA0017 from Airfoil database and save it in .txt format.
• Then we will add z co-ordinates as 0 since we want to get 2d sketch.
• Then we will go for creating a new part where we will first select MKS system and then insert the curve with the saved .txt file using the curve through XYZ option.
• Then we will create a proper sketch of the airfoil now we will rotate the sketch according to the angle of attack mentioned one by one (for each angle of attack create new part and sketch )and then extrude it.
• Now we will start the flow wizard and insert inputs like time and velocity i.e. 600m/s.
• Then we will adjust the computational domain in 2d and aslo set the length and height of the domain as required.
• Then we will insert the goals which are global goals - Force (x and y), friction force(x and y) and surface goals - force(x and y).
• Then we will insert the local mesh where we will set the refinement of mesh near the surface upto 3.
• Then we will run the stimulation and once the stimulation ends ,we will select a cut plot of velocity and also get the results of goals and get the plots for drag force(SG-X) and Lift force(SG-Y) as well.

OUTPUTS:

CASE 1: For angle of attack = 0 degree

Velocity cut plot:

Drag force:

Lift force :

Goal Summary :

CASE 2: For angle of attack = 2 degree

Velocity cut plot:

Drag force:

Lift force :

Goal Summary :

CASE 3: For angle of attack = 4 degree

Velocity cut plot:

Drag force:

Lift force :

Goal Summary :

CASE 4: For angle of attack = 6 degree

Velocity cut plot

Drag force:

Lift force :

Goal Summary :

CASE 5: For angle of attack = 8 degree

Velocity cut plot

Drag force:

Lift force :

Goal Summary :

CASE 6: For angle of attack = 10 degree

Velocity cut plot

Drag force:

Lift force :

Goal Summary :

CONCLUSION :

• so from the analysis we can say that as angle of attack increases the lift force also increases.
• At 0 degree angle of attack there is no lift force.