Difference between revisions of "OpenFOAM/C3/Turbulent-Flow-in-a-Lid-driven-Cavity/English"

Learning Objectives

• Solving turbulent case in OpenFOAM and
• Plotting streamlines in ParaView

System Requirement

• Linux operating system Ubuntu version 12.04
• OpenFoam version 2.1.1
• ParaView version 3.12.0

System Requirement

• The tutorials were recorded using the versions specified in previous slide

• Subsequently the tutorials were edited to latest versions

• To install latest system requirements go to Installation Sheet

Prerequisites

• Turbulence modelling
• Knowledge of how to solve flow in a Lid driven cavity
• If not so please refer to the relevant tutorial on our website.

Set up working Directory

Please make a note - this problem is already set up in pisoFoam solver in OpenFoam directory.

The boundary conditions are the Lid velocity U is 1 m/s

And we are solving this for a Reynolds number Re =10000

Type cd tutorials

Now type cd space tutorials and press Enter.

Two Folders les and ras

Cavity folder inside RAS

In this you will see two folders les and ras

Our problem is setup inside ras folder which is called as reynolds averaged stress.

ls

Now type cd space ras and press Enter.

Now type ls and press Enter.

ls

Type cd space cavity and press Enter.

Now type ls and press Enter.

Boundary and Initial conditions

0 folder

The initial conditions are specified within the files in the '0' directory.

Let us take a look at the files in the '0' directory.

Type ls

Now type ls and press Enter.

These files are to be kept as default until the inlet parameters don't change.

If any changes are to be done please refer to the tutorial on Simulating flow in a channel using OpenFoam, to calculate these values.

Let me clear this off.

Type ls

To do this type cd space constant and press Enter.

Now type ls and press Enter.

• the geometry of the case inside blockMeshDict
• and the fluid properties.

Let us open these two files.

Scroll down.

RASProperties contain the Reynolds average stress model for this case, which is kept as kEpsilon

Close this.

Scroll down.

The simulation type model for this case is kept as RASModel.

Close this.

Change the value of viscosity

To do this, in the terminal type gedit space transportProperties and press Enter.

The transportModel we are using here is Newtonian and the Viscosity is kept as 1 e raise to -4

Close this.

The system folder is to be kept default

So we need not go inside the polyMesh folder and look at the blockMeshDict file.

It can be kept as it is.

We will keep the system folder default as there are no changes inside it.

blockMesh

Meshing is done

We can mesh the geometry.

To do this in the terminal window type blockMesh and press Enter.

Meshing has been done.

To do this in the terminal type pisoFoam and press Enter.

The iterations running can be seen in the terminal window.

It may take some time for the iterations to stop.

To visualize the results let us open the ParaView window.

To do this in the terminal type paraFoam and press Enter.

This will open the ParaView window.

Lid driven cavity geometry

Change the drop down menu from solid color to U

You can see the lid driven cavity geometry.

A common visualization is surface plots.

Change the display to Surface in the column and from the drop down menu change from solid colour to U

You can see the initial condition of velocity.

Toggle on the color legend

Click on the Play button.

You can see the motion of the fluid inside the cavity.

You can also toggle on the colour legend on the left hand side top of ParaView active variable control menu.

Click on it. You can see the colour legend.

Filters > Common > Stream Tracers

• On top of the menu bar of ParaView
• Go to Filters > Common and Stream Tracers
• Click on it

You can see the stream lines at the centre of the lid driven cavity.

To do this , scroll down.

You can see the seed type.

Click on the Y axis

Click on the X axis

Delete this.

Select any one of these axis in which you would like to view the stream lines.

I will select the Y axis and click Apply.

You can see the streamlines along the Y axis.

Similarly you can select the X axis and plot the streamlines along the X axis.

Now delete this.

Save as .csv format

To do this go to Filter > Data Analysis and Plot over line.

Save the data as dot csv file from the file menu.

Click on Save Data.

Validate the results with Ghia et.al.

For Re= 10000

Now let me switch back to the slides.

The results obtained can be validated by using results of Ghia et.al for Reynolds Number , Re is equal to 10000

Summary

Let us summarise.

• Turbulent Flow in a Lid Driven Cavity
• and plotting stream lines in ParaView

This brings us to the end of the tutorial.

• Modify the grid size of the cavity

• Change it to (100 100 1)

• And visualise the results in ParaView using streamlines

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