Difference between revisions of "OpenFOAM/C2/Simulating-flow-in-a-Lid-Driven-Cavity/English"

The Lid Driven Cavity file structure

Meshing the Geometry

Solving and post-processing results in Paraview

Plotting & validating results on a spreadsheet.

System Requirement

I am using Linux Operating system Ubuntu version 10.04 .

OpenFOAM version 2.1.0

ParaView version 3.12.0

About Lid Driven Cavity flow

case for validation of a CFD code

The boundary conditions remain the same.

A moving wall and three fixedwalls

We are solving this for Reynolds no (Re) = 100

The moving wall has a velocity of 1 meters per second

Now Open a command terminal and

To do this press Ctrl+Alt+t simultaneously on your keyboard

In the command terminal type the path for lid driven cavity

type run and press enter

cd (space) tutorials and Press enter

cd (space) incompressible and Press enter

cd (space) icoFoam (Note that F here is capital) and Press enter

type cd (space) cavity and Press Enter

type ls and press enter

In the file structure of cavity you will see 3 folders :

0 , constant , and system.

Now type ls and press enter

The constant folder contains another folder named polymesh

and a file describing the physical properties of fluid.

Now type cd (space) polymesh and Press Enter

Polymesh contains a file named blockMeshDict

Now type ls and press enter

You can see the blockMeshDict

To view the file type gedit blockMeshDict

(Note that M and D here are capital)

Now press enter

This will Open up the blockMeshDict file

Let me drag this to the capture area

This contains :

-cordinates for lid driven cavity

-blocking and meshing parameters

-and boundary patches.

Since there are arcs as well as no patches to be merged

edges and mergePatchPairs can be kept empty.

Now close this

do this twice

you will come back to the cavity folder

Now type cd (space) system and press enter,

Now type ls and press enter

this contains three files

controlDict, fvSchemes and fvSolutions

controlDict contains control parameters for start/end time.

fvSolution contains discritization schemes used in run time.

fvSchemes contains equation for solver,

tolerance etc.

Now type cd ( space ) 0 (zero) and Press enter

Now type ls and press enter

This contains the initial values for boundary conditions like

Pressure ,Velocity,Temperature etc.

Type cd ( space ) (dot dot) . . to return to the cavity folder.

We are using a course mesh here.

Mesh the geometry by typing blockMesh in the terminal.

Now type blockMesh (Note that M and D here is capital)

and press enter

The meshing is done.

If there is some error in the blockMesh file

it will be shown in the terminal.

To view the geometry

Type paraFoam , Note that F here is capital

and press enter

Now on the left hand side of the object inspector menu click on Apply.

You can see the lid driven cavity geometry

close this

Note that M here is capital

and press enter

you can see the the number of cells ,

skewness and other parameters

which are associated with the mesh

let me switch back to the slides.

icoFoam is a Transient solver for incompressible flow of newtonian fluids.

In the terminal type icoFoam

Note that F here is capital

and press enter

Iterations running will be seen in the terminal window.

type paraFoam in the terminal

to view the geometry and the results

click on Apply

Now Scroll down the properties panel

of the objector inspector menu

for time step,regions and volume fields etc

Check or uncheck these boxes in the mesh part

to view the different boundary regions of Lid driven cavity

Now after this on top of the active variable control

dropdown menu change from solid color to capital p or U

which are the initial conditions such as pressure or velocity

I will select capital U

Now this will show the initial condition of velocity

Now on top of the paraview window you can see the VCR control

Click on the play button

Now this is the final result of velocity for lid driven cavity

Toggle on the color legend by clicking on

top left of the active variable control menu

This is the color legend for U velocity

We need to validate the results obtained

To do this let us plot the U and V velocity

For this Go to Filters Menu > Data Analysis > Plot Over line

Click on it

You can see the X , Y and Z axis

Select the X & Y axis turn by turn.

I will select the X axis and click Apply

You can see the Pressure and velocity plots being plotted.

we need to plot the graph for u/U v/s y/L for Reynolds number =100

To do this in Plot Data click on the Y-axis

And click APPLY

You can see the plot

In menu bar go to File > Save Data

Give and appropriate name to your file

I will give this as cavity

The file will be saved as .csv file

Now click ok

Again click ok

Now go to the cavity folder of openfoam directory.

Scroll down you can see the cavity.csv file

Open it in Open office or LibreOffice Spreadsheet

In the libreoffice spreadsheet copy

the U0 (u velocity) and to the right points1(Y-axis) columns

in another spreadsheet

Now divide both these coloumns

that is u zero by capital U and points 1 by capital L

Plot the results in libreoffice charts option on top of the menu bar.

Now let me switch back to the slides

Results obtained from Fluent.

Summary

File structure of Lid Driven cavity

Solved lid driven cavity.

Post-processing of results

Validation

Assignment

Change some parameters in the lid driven cavity

• Velocity Magnitude in the 0 folder
• Kinematic viscosity in transportPorpoerties in constant folder

Plot the results of u/U and y/L

This brings us to the end of the tutorial.

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