| Visual Cue
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Narration
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| Slide 1
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Hello and welcome to the spoken tutorial on Simulating Laminar Flow in a Channel using openfoam
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| Slide 2 : Learning Objectives
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In this tutorial I will show you
2D geometry of channel and initial boundary conditions
Meshing the Geometry
Solving and Post Processing results in Paraview
Validation with analytic result.
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| Slide 3:
System Requirement
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To record this tutorial
I am using GNU / Linux Operating system Ubuntu 10.04 .
OpenFOAM version 2.1.0
ParaView version 3.12.0
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| Slide 4: Prerequisite
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You should know how to create geometry using OpenFOAM
If not, please refer to the relevant tutorials on the Spoken Tutorial website
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| Slide 5 : About channel flow
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We simulate flow in a pipe so as to determine the flow development length along the downstream
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| Slide 6 : Diagram
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The boundary names and inlet flow is shown in this figure
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| Slide 7 :
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The flow develpoment length is given by the formula
L= 0.05 * Re * D
The pipe is of length 5 m and height 1 m.
Inlet velocity is 1 m/s.
Reynolds number ( Re ) is 100.
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| Solver: simpleFoam
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This is a steady state problem
Therefore we are using a steady state incompressible solver for this case
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| Demo:
SimpleFoam in incompressible flows
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We need to create a folder for our case.
The folders should be created inside the solver type you choose.
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| Demo
Create a floder and name it as channel in simpleFoam folder
copy 0,constant and system from pitzDaily to this channel folder
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I have already created a folder in simpleFoam folder of incompressible flow solvers
The folder is named as channel
Copy 0,Constant and System folders of any other case file in simpleFoam
Here i have copied the file structure of case of pitzDaily
Paste it in the channel folder created and make the necessary changes in the geometry,boundary faces and boundary condition
We will now see the file structure
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| Press Ctrl+Alt+t keys simultaneously
Type in command terminal
run and press enter
tutorial and press enter
incompresible and press enter
simpleFoam and press enter
channel and press enter
ls and press enter
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Open a command terminal by pressing Ctrl+Alt +t keys simultaneously on your keyboard.
In the command terminal type the path for channel case
Type run and press enter
type tutorials and press enter
type incompressible and press enter
type simpleFoam and press enter
type channel and press enter
now type ls and press enter
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| Type in command terminal
cd constant and press enter
ls and press enter
polymesh folder and 2 other files
gedit RASProperties and press enter
gedit transportProperties and press enter
In terminal type
cd polyMesh and press enter
in terminal type:
gedit blockMeshDict and press enter
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In this you will see three folders 0 , Constant and System
type cd constant and press enter
type ls and press enter
in this you will see files containing properties of fluid and a folder named polymesh
RASProperties containes Reynolds-averaged stress model
transportProperties contains transport model and
value of kinematic viscosity (nu) set at 0.001 m²/s.
Now type cd polyMesh and press enter
This contains the file blockMeshDict
To open the blockMeshDict file in the terminal type gedit blockMeshDict and press enter
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| Refer to earlier tutorial for creating simple geometry in OpenFOAM
in terminal cd space .. twice and press enter
In terminal type:
cd space 0 and press enter
type ls and press enter
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To set up the blockMeshDict file refer to the tutorial for creating simple Geometry in OpenFOAM.
The geomery is in meters so the convertTometers is set to 1
next we have defined the vertices of the pipe
we have used a 40 X 40 mesh size here and cell spacing of
( 1 1 1 )
next we have the boundary conditions and their types which are set as inlet ,outlet,top,bottom
Since it is a 2D problem frontAndBack is kept empty.
We have entered here the type of boundary and their faces
Arcs and mergePatch pair is kept empty.
Close the blockMeshDict file
Type cd ..(dot dot and press enter after each) twice to go back to the channel folder
Now type cd 0 (Time directory) and press enter
Type ls and press enter
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| In the terminal you can see the files
Slide 7 : formula to calculate epsilon and k.
Do not chnge the values of nu,nuTilde and R
Change only the boundary names
in terminal type : cd .. and press enter
System folder is kept default
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This contains the intial boundary conditions and wall functions for the channel case
It should contain various files named epsilon ,k, nu ,nuTilda which are the wall functions and
p , R and U are initial conditions of the flow
Calculate epsilon and k from the formula given in the
figure and enter it in the file.
Change only the boundary names in each of the above folder.
Note that the values in nu,nuTilde and R are to kept default
Changes are only made in boundary condition names.
Rest of the files should contain initial value for each of the boundary faces.
Now Type cd (space) ..(dot dot) and press enter
There is no change in the system folder
We need to mesh the geometry
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| In terminal type:blockMesh and press enter
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In the command terminal type blockMesh and press enter
Meshing is done
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| Slide 7 :simpleFoam
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The type of solver we are using here is simpleFoam
It is a Steady-state solver for incompressible, turbulent flow
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| Type simpleFoam and press enter
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In the command terminal type simpleFoam and Press enter
Iterations running will be seen in the terminal.
The iterations will stop once the solution is converged or it reaches end time value.
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| In terminal
type: paraFoam and press enter
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To view the results in paraview in the terminal
type paraFoam and press enter
This will open up the paraviw window
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| Demo
Solid color to U
initial state at inlet boundary
click on the play button
final contour of velocity
toggle color legend on from left hand side top
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On let hand side of the paraview window click Apply
The geometry can be seen here.
In top of active variable control menu change the drop down menu from solid color to capital U.
You can see the initial state of velocity magnitude at inlet.
On top of the paraview window click on the play button of VCR control menu
you can see the final value of velocity magnitude.
Also toggle on the color legend from left hand side top of active variable control menu.
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| Demo
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We can see that once the flow has fully devloped it attains a maximum uniform velocity at center.
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| Slide 8:Validation
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The results obtained can be validated with the analytical solution for laminar flow in a pipe which is u(max)=1.5 Uavg
Using openfoam we obatain a velocity of 1.48 m/s which is a good match.
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| Slide 9 : Summary
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In this tutorial we learnt
File structure of channel
Obtained solution using steady state solver
Viewed the geometry in paraview
Validation with analytic results
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| Slide 10 :
Assignment
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As an assignment:
Solve the problem for Reynold Number 1500 and validate it with the analytical result
this brings us to the end of the tutorial
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| Slide 11 :
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The video available at this URL:
http://spoken-tutorial.org/What_is_a_Spoken_Tutorial
It summarizes the Spoken Tutorial project.
If you do not have good bandwidth, you can download and watch it.
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| Slide 12 :
About Spoken tutorials
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The Spoken Tutorial Project Team
-Conducts workshops using spoken tutorials
-Gives certificates to those who pass an online test
-For more details, please write to contact@spoken-tutorial.org
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| Slide 13
Acknowledgement
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Spoken Tutorials are part of Talk to a Teacher project,
It is supported by the National Mission on Education through ICT, MHRD, Government of India.
This project is coordinated by http://spoken-tutorial
More information on the same is available at the following URL link http://spoken-tutorial.org/NMEICT-Intro
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| Slide 14:
About the contributor
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This is Rahul Joshi from IIT BOMBAY signing off.
Thanks for joining.
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