Flow over an airfoil

Aim:

To made a flow simulation on NACA airfoil and to analyse the various results on the airfoil by changing the angle of attack of the airfoil.

Objectives:

• To model the airfoil using the provided data.
• To made a time dependent external flow simulation on the airfoil with 0 degree angle of attack.
• To analyse the lift and drag force of the airfoil surface.
• To change the angle of attack to 2,4,6,8 and 10 degrees and to analyse the lift and drag force for all the cases.
• To compare the results of all the cases.

NACA airfoil:

The NACA stands for National Advisory Committee for Aeronautics. The NACA suggested a series of airfoil shaped wings for the aircraft. The made the nomenclature by initializing with NACA and followed by four digit numbers. The four digits has a specific nature. The first digit is ment for exhibiting the maximum camber as a percentage of chord. Camber is defined as the asymmetry between the two surfaces of the airfoil. The leading edge and the tailing edge of the airfoil is connected by a straight line called chord. The second digit explaines the length or distance of the maximum camber from the leading edge of the airfoil. The last two digits explains the maximum thickness of the chord.

The angle of attack is defined as the angle between the reference line of the body to the vector line indicating the relative motion of the body and the fluid.

NACA airfoil modelling:

The NACA airfoil is modelled based on the coordinate values obtained from the NACA airfoil data base. Initially, the simulation is done with the 0 degree of angle of attack. The airfoil is designed based on 6 types of angle of attack. The angle of attack is varied with the values of 0,2,4,6,8 and 10 degrees.

a) Airfoil with 0deg of Angle of attack:

The airfoil is designed with 0 deg of angle of attack.

b) Airfoil with 2deg of angle of attack:

The airfoil is designed with 2 deg of angle of attack.

c) Airfoil with 4deg of angle of attack:

The airfoil is designed with 4 deg of angle of attack.

d) Airfoil with 6deg of angle of attack:

The airfoil is designed with 6 deg of angle of attack.

e) Airfoil with 8deg of angle of attack:

The airfoil is designed with 8 deg of angle of attack.

f) Airfoil with 10deg of angle of attack:

The airfoil is designed with 10 deg of angle of attack.

Simulation setup:

The new wizard is opened and some basic simulation constraints are assigned. The external flow is mentioned along with the time dependent parameters. For all the cases, the fluid velocity is assigned as 600m/s along x-axis.

The computational domain is enlarged or changed to specific length and breadth to get the clear vision of the simulation. The computational domain is edited to 2D parameters in xy plane.

The global goals is assigned to get the plot of force along x and y directions. Also the global goals are assigned for friction force on x and y direction. The ultimate aim of the simulation is to find the lift and drag forces. To find the lift and drag forces the surface goal is assigned with friction force of x and y direction. The integral or surface force along y axis is called as lift force. The integral or surface force along x axis is called as drag force.

The refined mesh is assigned for the 2D apparatus. The local mesh is assigned on the surface of the airfoil in a refined way to get the very accurate results on the surface of the airfoil.

Results and discussions:

a) Airfoil with 0deg angle of attack:

The calculation setup for the airfoil explains the movement of the airfoil virtually by enabling the preview option.

The drag force and lift force plots of the airfoil is attached below,

Drag force:

The maximum drag force acted on the airfoil is about 160N for allowing the air with the velocity of 600m/s.

Lift force:

The lift force varies simultaneously and achieved a maximum force of about 3N.

Velocity plot:

The cut plot images of velocity with and without considering the mesh is shown below,

b) Airfoil with 2deg angle of attack:

The calculation window which has the preview of the airfoil motion is shown below,

Drag plot:

The maximum drag force of nearly 170N was attained by the airfoil with 2 deg angle of attack.

Lift plot:

The lift force is attained a maximum value of nearly 380N with 2 deg angle of attack.

Velocity plot:

The cut plot image which represent the velocity of the airfoil is shown below,

c) Airfoil with 4deg angle of attack:

The calculation image for the airfoil with 4 deg of angle of attack is shown below,

Drag force:

The drag force attained its maximum value of nearly 210N with the angle of attack of 4 deg in the airfoil.

Lift force:

The maximum lift force of the airfoil goes to the value of nearly 780 N at the airfoil with angle of attack of 4 deg.

Velocity plot:

The velocity cut plot of the airfoil with 4 deg of angle of attack is shown below,

d) Airfoil with 6deg angle of attack:

The calculation image with the motion preview of the airfoil with 6deg of angle of attack is shown below,

Drag force:

With the angle of attack of 6 deg, the drag force attained to the maximum value of nearly 280N.

Lift force:

The lift force riseup to the maximum extend of 1200N at 6deg angle of attack.

Velocity plot:

The cutplot that indicates the velocity of the airfoil is shown in the below image,

e) Airfoil with 8deg angle of attack:

The calculation image of the airfoil is shown below,

Drag force:

The drag force reaches its maximum value at nearly 370N in the airfoil with 8 deg angle of attack.

Lift plot:

The airfoil lift reaches its maximum value of 1600N with the angle of attack of 8deg.

Velocity plot:

The velocity cut plot of the airfoil with 8 deg of angle of attack is shown below,

f) Airfoil with 10deg angle of attack:

The calculation image of the airfoil with 10 deg angle of attack is shown in the figure,

Drag force:

The 500N is the maximum drag force attained by the airfoil with 10 deg angle of attack.

Lift force:

The 2000N is the maximum lift force attained by the airfoil with 10 deg of angle of attack.

Velocity plot:

The cutplot that indicates the velocity of the airfoil is shown below,

Results comparison:

The overall result values for all the cases are shown below,

a) Airfoil with 0 deg of angle of attack:

b) Airfoil with 2 deg of angle of attack:

c) Airfoil with 4 deg of angle of attack:

d) Airfoil with 6 deg of angle of attack:

e) Airfoil with 8 deg of angle of attack:

f) Airfoil with 10 deg of angle of attack:

From the results obtained in various cases various datas are obtained regarding drag and lift forces of the airfoil,

• The drag force increases with increase in the angle of attack.
• The drag force value increased from 158N to 494N by increasing the angle of attack from 0 to 10.
• The lift also increases with increase in angle of attack.
• The lift force value increased drastically from 3.18N to 1991N by increasing the angle of attack from 0 to 10.
• The drag force and the lift force are directly proportional to the angle of attack.
• The drag force increased because when the angle of attack increases, the area against air also increases.
• The greater angle of attack lift the airfoil to the maximum height.

Conclusion:

Thus, from the NACA airfoil simulation the importance of angle of attack in the drag and lift forces of the airfoil is analysed.