Simulating Flow over an airfoil using SolidWorks

AIM

To model flow over NACA airfoil for angle of attack of 0,2,4,6,8,10 degrees.

THEORY

Airfoil is defined as cross section of a body that is placed in an airstream in order to generate useful aerodynamic force. NACA stands for national Advisory Committee for Aeronotics. The NACA airfoils are airfoil shapes for aircraft wings.

Angle of Attack

It is the angle at which relative wind meets the airfoil. It is the angle formed by the chord of the airfoil and the vector representing the relative motion between aircraft and the atmosphere.

PROCEDURE

i) The data for an airfoil is selected. In order to generate the curve of the airfoil in SolidWorks, the data needs to be editted as the data contains only the x and y values of the curve. However, we need z coordinate as well. Therefore, z coordinate for every point of the curve is set to 0.

ii) Once the curve is imported, front plane is selected to sketch and convert entity is used to get the sketch of the curve on the front plane. Line tool is used to join the open ends of the curve.

iii) The curve is rotated about the origin as per the angle of attack, i.e. for angle of attack =2, the angle of rotation is set to `-2^o` and so on.

iv) After the desired settings are made, the curve is extruded and the part is saved.

v) External flow simulation is set to the airfoil with air as the fluid. A velocity of 600 m/s is provided to the X-direction.

vi) Rigth clicking on the computational domain, edit definition is clicked and 2-D simulation is selected on the XY plane. The size of the computational domain is selected such that there is a space of about 10-15 times the chord length in front and about 5 times the chord length at the back of the airfoil. Suitable vertical directions are also selected.

vii) A local mesh is inserted to the upper surface of the airfoil with finer grain structure for better results. Global and surface goals are provided.

viii) Simulation is run. Since the flow is in supersonic region, the simulation needs to be stop manually after a near constant value of the goal plot (lift force taken in this case) is achieved.

ix) Cut plots for pressure and velocity and goal plots (drag and lift force) for different angles of attack is generated.

RESULTS

Angle of attack = 0

Angle of Attack = 2 degrees

Angle of attack = 4 degrees

Angle of attack = 6 degrees

Angle of attack = 8 degrees

Angle of Attack = 10 degrees

Comparison of drag force for different angles of attack

Comparison of lift force for different angles of attack

CONCLUSION

i) With increase in angle of attack, the number of iterations required to achieve the results decreases.

ii) With increase in angle of attack, increase in lift force is higher as compared to increase in drag force. Drag force increases at a slower rate.

iii) The velocity over airfoil increases with increase in angle of attack.