Flow over an airfoil

AIM: To perform the external flow simulation over NACA airfoil for different angle of attack and compare the results

Theoritical background:

Air foil

An airfoil or aerofoil is the cross-sectional shape of a wing, blade, or sail. 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.

Angle of Attack

In fluid dynamics, angle of attack () is the angle between a refrence line on a body (often the chord line of an airfoil) and the vector representing the relative motion between the body and the fluid through which it is moving. Angle of attack is the angle between the body's reference line and the oncoming flow.

In aerodynamics , angle of attack specifies the angle between the chord line of the wing of a fixed wing aircraft and the vector representing the relative motion between the aircraft and the atmosphere. The lift coefficient of a fixed wing aircraft varies with angle of attack. Increasing angle of attack is associated with increasing lift coefficient up to the maximum lift coefficient, after which lift coefficient decreases.

Modelling:

Meshing

Computational Domain:

Case 1: Angle of attack = 0 degree

Velocity contour

Pressure contour

Case 2: Angle of attack = 2 degree

Velocity contour

Pressure Contour

Case 3: Angle of attack = 4 degree

Velocity Contour

Pressure contour

Case 4: Angle of attack = 6 degree

Velocity Contour

Pressure contour

Case 5: Angle of attack = 8 degree

Velocity Contour

Pressure contour

Case 5: Angle of attack = 10 degree

Velocity Contour

Pressure Contour

TABULATION:

The results of Average value of drag and lift forces for different angle of attack are tabulated below

Observations:

As the angle of attack increases the drag force also increases , but the lift force decreases and reaches a negative trend. Here the lift force is acting in the perpendiular direction to that of the drag force. Angle of attack changes the airflow direction, which causes variation in pressure and velocity of boundary layer separation.