Flow over an airfoil

AIM:

To do a flow analysis over a NACA Airfoil at different angle of attacks using SOLIDWORKS.

THEORY:

The NACA Airfoils are airfoil shapes for aircraft wings developed by the National Advisory Committee for Aeronautics. The shape of the NACA airfoils is describes using a series of digits following the word ‘NACA’. The parameters in the numerical code can be entered into equations to precisely generate the cross-section of the airfoil and calculate its properties.

An airfoil shaped body moving through a fluid produces an aerodynamic force. The component of this force perpendicular to the direction of the motion is called lift. The component parallel to the direction of the 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.

The NACA four digit wing sections define the profile by:

• First digit describes maximum camber as per percentage of the chord.
• Second digit describes the distance of camber from the airfoil leading edge in tens of percent of the chord.
• Last two digits describe maximum thickness of the airfoil as percent of the chord.

The NACA 0018 airfoil is symmetrical; the 00 indicates that it has no camber. The last two digits 15 indicate that the airfoil has a 17% thickness to the chord length ratio; it is 17% as thick as it is long.

PROCEDURE:

• Start with choosing an airfoil profile from --- Here I have used NACA0018 profile.
• Now load the profile in Solidworks by clicking curves and then select the text file for loading the curve profile. Then rotate the sketch for 2, 4, 6, 8, and 10 degrees. Then use “Convert Entity” for creating a sketch and then extrude it.
• Start with the flow simulation, click on “Wizard” and then select the external flow, the fluid used here is Air, and velocity is 600 m/s.
• Now adjust the computational domain to an appropriate length.
• Now set the surface goals, force in x-direction is the drag force and in y-direction is the lift force.
• Now create a local mesh for finer refinement near the surface of the airfoil. Now run the simulation.

RESULTS:

FOR 0 DEGREE ANGLE OF ATTACK

FOR 2 DEGREE ANGLE OF ATTACK

FOR 4 DEGREE ANGLE OF ATTACK

FOR 6 DEGREE ANGLE OF ATTACK

FOR 8 DEGREE ANGLE OF ATTACK

FOR 10 DEGREE ANGLE OF ATTACK

PLOT OF AVERAGE DRAG AND AVERAGE LIFT vs ANGLE OF ATTACK

CONCLUSION:

We can see from the last graph that lift forces and drag forces both increases as the angle of attack increases. Also it can be seen that the lift forces increases linearly as the angle of attack increases, whereas the drag force increases parabolically. The maximum lift force is attained at 10 degree angle of attack. There is no or negligible lift force at 0 degree angle of attack but the drag force is quite high.