Flow over an airfoil

Aim: To Perform Transient Flow analysis over NACA 0017 airfoil using Solidworks Flow Simulation.

Theory: Airfoil geometry can be characterized by the coordinates of the upper and lower surface. It is often summarized by a few parameters such as maximum thickness, maximum camber, the position of max thickness, the position of max camber, and nose radius. One can generate a reasonable airfoil section given these parameters. This was done by Eastman Jacobs in the early 1930's to create a family of airfoils known as the NACA Sections.

Mean Camber Line: Set of points halfway between upper and lower surfaces

Measured perpendicular to the mean camber line itself

Leading Edge: Most forward point of the mean camber line

Trailing-Edge: Most reward point of the mean camber line

Chord Line: Straight line connecting the leading and trailing edge

Chord, c: Distance along the chord line from leading to trailing edge

Chamber: Maximum distance between mean chamber line and the chord line

Measured perpendicular to the chord line

NACA (National Advisory Committee for Aeronautics) or NASA (National Aeronautics and Space administration) Identified different airfoil shapes with a logical numbering system. Before the NACA series, airfoil design was rather arbitrary with nothing to guide designers except experience with known shapes and experimentation with modified shapes.

NACA 4-digit series

NACA 5-digit series

NACA 1-series or 16-series

NACA 6-series

NACA 7-series

NACA 8- series

NACA Four-Digit Series

The first digit specifies maximum camber in the percentage of chord

The second digit indicates the position of maximum camber in tenths of chord

The last two digits provide a maximum thickness of airfoil in the percentage of the chord.

Reason for using Transient Simulation instead of Steady-State Simulation

The reason for using Transient Simulation is that Lift Coefficient is not necessarily a transient changing quantity, e.g. If we analyze the Laminar Flow over an airfoil under a 0-degree angle of attack than the result will not be changeable with respect to time.

But for Turbulent Flow and higher angle of attack, the flow around the airfoil is subjected to flow separation on the upper side of the airfoil, and separating flow will generate transient vortices, which are connected by the main airstream to downstream. This is causing the pressure field around the airfoil to transiently change with the movement of vortices and consequently lift coefficient is becoming a changeable quantity over time.

Procedure:

1. In this we will first download NACA airfoil coordinates from the airfoil tool which will be downloaded as CSV file and then we will open notepad and then we will copy the text X, Y and Z coordinates and the save it.
2. Now we will open Solidworks and then go for part modeling and then in a feature, we will go to curve and then we will browse the file and click on open and then ok to open the file.
3. Now our airfoil is produced, We will go to Front Plane and then we will click on convert entities to convert it into a sketch.

Note: If we have open airfoil then we have to add a line at the end of the airfoil and if it is a closed airfoil then there is no need to add anything.

4. Now since at first, we are designing for a 0-degree angle of attack we are not going to rotate the airfoil sketch.
5. Now we will go to features and then Extrude boss/base and then we will extrude it to 2mm using the midplane and then we will save our file.
6. Now we will go to Solidworks Flow Simulation and then we will go to the wizard and then we will define it as an external flow problem, switching on the time dependency the fluid will be air and X- velocity to be 600 m/s.
7. We will get an automatically generated computation domain and then we will edit the domain and we will keep a distance of 10-15 times from the leading edge and 20-25 times from the trailing edge to get a better plot of the contours.
8. We will now go to mesh and then insert local mesh and then select the top face of the airfoil and then refinement to 3.
9. Now we will add the goals and then we will go to Global goals and then we will add X Force, Y Force, X Frictional Force, and Y Frictional Force, and then we will go to Local goals and then we will add X Force and Y Force.
10. Now we will run the simulation for our results. Now after getting the results we will plot Pressure and Velocity Contour.
11. We will repeat the steps just the changes we will do that after converting the sketch we will rotate it in which the entities to rotate would be the sketch and then rotation about would be the front axle and degree would be -2 degree and simultaneously for all the cases.

Computation Domain:

Local Mesh:

Results and Plots:

0-Degree Angle of Attack

Model

Velocity Contour:

Pressure Countour:

Global Goal Force:

Global Goal Friction Force:

Surface Goal force:

Goal Report:

2-Degree Angle of Attack

Model

Velocity Contour:

Pressure Countour:

Global Goal Force:

Global Goal Friction Force:

Surface Goal force:

Goal Report:

4-Degree Angle of Attack

Model

Velocity Contour:

Pressure Countour:

Global Goal Force:

Global Goal Friction Force:

Surface Goal force:

Goal Report:

6-Degree Angle of Attack

Model

Velocity Contour:

Pressure Countour:

Global Goal Force:

Global Goal Friction Force:

Surface Goal force:

Goal Report:

08-Degree Angle of Attack

Model

Velocity Contour:

Pressure Countour:

Global Goal Force:

Global Goal Friction Force:

Surface Goal force:

Goal Report:

10-Degree Angle of Attack

Model

Velocity Contour:

Pressure Countour:

Global Goal Force:

Global Goal Friction Force:

Surface Goal force:

Goal Report:

Drag Force:

Lift Force:

Drag vs Lift

Observations:

1. It has been observed that with an increase in the angle of attack drag force increases and hence vice versa.
2. It has been also observed that an increase in the angle of attack lift force also increases and hence vice versa.
3. We can also find the drag and lift coefficient of the different airfoil and can choose the airfoil which suits in its application
4. If we do Transient analysis animation of different quantities, we will get behavior changes with respect to time.