OpenFOAM/C2/Supersonic-flow-over-a-wedge/English

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Title of script: Supersonic flow over a wedge using OpenFOAM.


Author: Rahul Ashok Joshi

Keywords: Video Tutorial,Computational Fluid Dynamics (CFD)

Click here for the slides

Visual Cue Narration
Slide 1

Hello and welcome to the spoken tutorial on Supersonic flow over a wedge using OpenFOAM.

Slide 2: Learning Objective In this tutorial I will show you

How to solve a compressible flow problem of supersonic flow over a wedge

How to Post process the results in paraView.

Slide 3: System Requirement To record this tutorial

I am using Linux Operating system Ubuntu 10.04

OpenFOAM version 2.1.0

ParaView version 3.12.0

Slide 4:Prerequisites To practice this tutorial you should have some basic knowledge of

Compressible flows and Gas Dynamics

Slide 5

Let us now solve supersonic flow over a wedge using OpenFOAM and see the shock structure formed using paraview.

The problem consists of a wedge with semi-angle of 15 degrees kept in a uniform supersonic flow

The Inlet velocity is 5 m/s

The boundary conditions are set as shown in the figure.

Slide 6 Solver

The type of solver I am using here is rhoCentralFOAM

It is a Density-based compressible flow solver

It is based on central- upwind schemes of Kurganov and Tadmor

Open a new terminal window

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

In the command terminal type the path for supersonic flow over the wedge

In the terminal Type 'run' and press enter.

Now type cd space tutorials and Press Enter 

                cd space compressible and Press Enter
                cd  space rhoCentralFoam and Press Enter
                cd space wedge15Ma5 this is the name of the folder of supersonic flow over a wedge in rhoCentralFoam and Press Enter

Now type ls and Press enter

You will see three folders: 0,constant and system.


Open the blockMeshDict file,

To do this type cd space constant and press enter

cd polyMesh -Note that M here is capital and Press enter

type ls and press enter

You can see the blockMeshDict file

To view the blockMeshDict file type gedit space blockMeshDict -Note that M and D here are capital and press enter

Let me drag this to capture area

Scroll down

In this you need to calculate the co -ordinates for the wedge

This has been already calculated and set up in the problem

The rest of the data remain the same.

In boundary patches the boundaries are set as shown in the figure

Close the blockMeshDict file

In the command terminal type cd space .. twice to return back to wedge folder

Now open the 0 folder

To do this type cd space 0 and press enter

Now type ls and press enter

This contains the initial condition for pressure, velocity, temperature etc.

Type cd space .. (dot dot) and press enter

Mesh the geometry using blockMesh utility To do this in the command terminal type blockMesh and Press Enter

Meshing has been done

Now to View the geometry in the command terminal type paraFoam and press enter

This will open the paraview window.

On the left hand side of the object inspector menu click APPLY

In this you can see the geometry is which is a rectangular section upstream and changes to a wedge downstream

Close the paraview window

Now run the solver 'rhoCentralFoam'

To do this in the command terminal type rhoCentralFoam and Press Enter.

The iterations running can be seen in the terminal window.

The iteration running will stop after it converges or at the end of the time step.

Now the solving has been done

To visualise the results let us open the paraview window once again

In the command terminal, type “paraFoam” and press Enter

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

On the left side top in active variable control menu you can see the drop down menu showing solid color.

Now click on it and Change from solid color to capital U.

Now make the color legend ON by clicking on left hand side top of active variable control menu.

Make the color legend ON

Click on it

On top of the paraview window you can see the VCR control.

Click on the play.

You can see the final results of U velocity

Now scroll down the properties in the object inspector menu on the left hand side

Now click on display besides Properties

Scroll down and click on rescale to size

You can see the final result of velocity magnitude.

Similarly you can select pressure

You can see the final value of pressure

Now close the paraview window

You can also calculate the Mach number for the flow

To do this we can use the openfoam utility by typing “Mach” in the command terminal

Type Mach- Note that M here is capital and press enter

You will see that the Mach number is calculated 

for each time step.

Again open the paraview window by typing in the command terminal paraFoam and press enter

Click Apply

Scroll down

In volume fields check the Mach number (Ma) box and again click apply.

On top of the active variable control menu click on solid color and change it to Ma

Again on the VCR control click play and make to color legend ON

You can thus see the mach number in the color legend and the corresponding colors.

We notice here that:

When the wedge is kept in a supersonic flow

produces a shock across which the flow properties

like temperature, pressure and density drastically changes.

Slide 7:

Now let me switch back to the slides

The solved tutorial can be validated with exact solution

available in basic books of aerodynamics by John D Anderson

Slide 8:

In this tutorial we learnt:

Solving a compressible flow problem

Velocity and pressure contour for the wedge

OpenFOAM utility for calculating Mach number

Slide 9: Assignment

Assignment:

Vary the wedge angle between 10 ° to 15 ° to view the shock characteristic for the flow

This bring us to the end of the tutorial

Slide 10 :About Spoken Tutorial

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.

Slide 11:Acknowledgement 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.org

More information on the same is available at this URL http://spoken-tutorial.org/NMEICT-Intro

About the contributor

The script is provided by Arvind N and This is Rahul Joshi from IIT Bombay signing off Thnks for joining

Contributors and Content Editors

Chandrika, DeepaVedartham, Nancyvarkey, Rahuljoshi

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