Difference between revisions of "OpenFOAM/C3/Creating-and-Meshing-aerofoil-in-Gmsh/English"

• How to create an aerofoil using Gmsh
• Mesh the created aerofoil

If not, for Gmsh please see the tutorial on Installing and running Gmsh on the spoken tutorial website.

System Requirement

• Ubuntu Linux Operating system version 14.04 and
• Gmsh version 2.8.3

Aerofoils are streamline shaped wings which are used in airplanes and turbo machinery.

These shapes are such that the drag force is a very small fraction of the lift.

The dat file

Download the dat file and Python script

I will download the .dat file and Python script from this url:

http://community.dur.ac.uk/g.l.ingram/download.php

http://community.dur.ac.uk/g.l.ingram/download.php

Open the Downloads folder

Download the .dat file and the Python script and go to the Downloads folder.

This file contains the calculated X and Y coordinates for each point that defines the aerofoil.

Z coordinate is kept as zero.

We need the X, Y and Z coordintes in Gmsh acceptable format.

This can be done manually but this is time consuming.

This Python script

• converts the data in the .dat file
• and gives the ouput in a separate file which is understood by Gmsh.

Type cd space Desktop

python dat2gmsh.py

naca5012xyz.dat

Now type ls.

We can see that a new file by the name naca5012xyz.dat .geo will be generated.

This contains the co-ordinates in Gmsh format.

Here nac_lc is the characterstic length which is defined in the first line which is 0.005

I will change this to 0.5

This is because we need a coarser mesh.

You can change this value according to your mesh requirement.

Now save this file.

This opens gmsh with the aerofoil.

You will note that the aerofoil has an open trailing edge.

Scroll down.

Now above spline, enter

Point(1046) = { 1.005, -0.0005, 0.00000, nac_lc};

Spline(1000) = {1000:1046,1000};

Save the geo file.

Enter these coordinates and change the prescribed mesh element size to 0.5

Press Enter.

(4 3 0)

(4 -3 0)

(-4 -3 0)

(-4 3 0)

(4 3 0)

(4 -3 0)

(-4 -3 0)

(-4 3 0)

Translate>extrude surface

Go to Translate >> Extrude Surface.

Click on boundary surface

• enter the coordinates for Z direction as 1
• and click on the boundary of the surface.

You can see that the geometry has been extruded.

Close the gmsh window

Layers{1};

Recombine;

Save this file.

This will ensure that the mesh is one element thick.

Gmsh automaticaly generates the mesh of the defined geometry.

Click on 1D mesh, 2D mesh and 3D mesh.

The mesh has been generated.

A new window will appear. In the drop down, change to the mesh format.

And type the name the file as aerofoil.msh

Note that here msh stands for the file type mesh.

Click Ok

Again click Ok

As an assignment create another aerofoil by using different dat file for different aerofoil shapes.

• How To create an aerofoil in Gmsh.
• How to do meshing in Gmsh

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