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

Learning Objectives

Solving turbulent flow case in OpenFOAM

Plotting streamlines in Paraview

System Requirement

OpenFoam version 2.1.1

Paraview version 3.12.0

Prerequisites

Turbulence modelling

Knowledge of how to solve flow in a Lid driven cavity

If not so please refer to the revelent tutorial on our website

Set up working Directory

conditions to the 'Lid Driven Cavity' problem discussed in the

basic level tutorial.

Please make a note this problem is already set up in

pisoFoam solver in OpenFoam directory.

The boundary conditions are Lid velocity , U =1m/s

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

turbulent flow of Newtonian fluids.

It is called pisoFoam

To do this press Ctrl+Atl+t keys simultaneously on your keyboard.

Go to the pisoFoam folder

Now type cd tutorials and press enter

type cd incompressible and press enter

type cd pisoFoam (Note that F here is capital ) and press enter

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

Now type cd ras and press enter

Now type ls and press enter

You can see the cavity folder

type cd cavity and press enter

Now type ls and press enter

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.

ls to view the files inside this folder

Do not edit the files unitil inlet parameters don't change

Refer to the earlier tutorial on channel flow for calculating these values

cd 0 and press enter

Now type ls and press enter

You can see files named as epsilon, k, nut, nutilda,p,R and U.

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

Let us open the constant folder.

To do this type cd constant and press enter

Now type ls and press enter

of the case inside blockMeshDict

And the fluid properties.

In this case you will see two more files

other than transportProperties named as

RASProperties and turbulenceProperties

Let us open these two files

Let me drag this to the capture area

Scroll Down

RASProperties contain the Reynolds average stress model for this case.

Which is kept as kepsilon

close this

gedit (space) turbulentproperties and press enter

turbulentProperties contain the turbulent model ,

Simulation type model for this case is kept as RASModel

Close this

Change the value of viscosity

In the terminal window type transportProperties and press enter.

The transportModel we are using here is Newtonian and

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

In the terminal type cd .. and press enter

We will keep the system folder default

As there are no changes inside it

blockMesh

Meshing is done

Now we can mesh the geometry

To do this in the teminal 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 till the iterations 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 visualisation is surface plots.

Change the display to Surface in the column and

from the drop down menu change from solid color to U

You can see the initial condition of velocity

Toggle on the color legend

Click the play button

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

You can also toggle on the color legend on the left hand side top

of paraview active variable control menu.

Click on it

Filters > Common > Stream Tracers

On the top menu bar of paraview

Go to Filters > Common > Stream Tracers

Click on it

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

You can also change the orientation in which the stream lines are viewed.

To do this , scroll down

You can see the seed type

Let me shift this to the right

and change the seed type from point source to line source

Click on the Y axis

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 streamlines along the X axis

Now delete this

Save as .csv format

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

Save the data as .(dot) csv file from 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 results obtained by Ghia et.al for Reynolds No , Re= 10000

Summary

Let us summarise

In this tutorial we learnt Turbulent Flow in a Lid Driven Cavity

And plotting streamlines in paraView

This brings us to the end of the tutorial

Modify the grid size of the cavity

Change it to (100 100 1)

Visualise the results in paraview using streamlines

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