Week 8 - Simulation of a backward facing step in OpenFOAM

HERE IS THE BOUNDARY CONDITION SPECIFICATION:

PROCEDURE:

So to start the simulation processwe need to start the terminal after starting we can see window here we have to simulate our problem

1 start with 'tut' its a tutorial short commandin openfoam tutorial directory here we need to type 'ls' which means list of tutorials present in it.

2 we have to solve the incompressible flow simulation for the problem so to select we need to type 'cd incompressible' after this we need to type again 'ls' to check the list of tutorial present init

3 we need to solve laminar viscous flow here we will select ' cd icoFoam' again in that we need to type 'ls' to check in

4 we can see two option both are the part of icoFoam solver and cavity section use to create domain and blockmesh so select 'cavity folder' by 'cd cavity'

5 in cavity we are again going to use cavity folder where we have to define domain and generate block mesh, but we are not going to make any changes here in toturial file .so we sre going to       copy this cavity folder by typing 'cp -r cavity $FOAM_RUN/cavity_test'.

6 and after that open run folder by typing '$FOAM_RUN' where we can see cavity_test file.

7 here now we can make any changes to cavity test file which we not affect the open foam 

8 by againg typing 'ls' we can see the script file inside it we can make changes in it by typing 'gedit in front of any script'.

9 so to make changs in blockmeshdict type 'gedit blockmeshdict' which will open the script file and can do changes in it as per shown below

10 so the next step is to navigate the controldict folder where we can specify the simulation time as we need .

11 after this again go back one step by typing 'cd ..' again we are here a one step back where we can 3 directory we can go into '0' where we see two script file 'u' 'p' for velocity and pressure we can again type 'gedit p' and make changes in it also same way to script file 'u'.

12 after all this we need to type 'blockmesh ' keep it run for while if there is any error we can see it.

13 after that we need to check mesh by typeing 'checkMesh' and we can se mesh is run and it is ok. if any error occur we need to identify the error solve it again run the same procedure.

14 after this we can type 'paraFoam' where we can see the goemetry .

CODE:

BOLCKMESHDICT

with out applying the grasing factor.

/*--------------------------------*- C++ -*----------------------------------*\
  =========                 |
  \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
   \\    /   O peration     | Website:  https://openfoam.org
    \\  /    A nd           | Version:  9
     \\/     M anipulation  |
\*---------------------------------------------------------------------------*/
FoamFile
{
    format      ascii;
    class       dictionary;
    object      blockMeshDict;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

convertToMeters 0.01;

vertices
(
    (0 0 0)
    (8 0 0)
    (8 0.5 0)
    (0 0.5 0)
    (8 1 0)
    (0 1 0)
    (20 1 0)
    (20 0.5 0)
    (20 0 0)
    (20 -1 0)
    (8 -1 0)
    
    (0 0 0.6)
    (8 0 0.6)
    (8 0.5 0.6)
    (0 0.5 0.6)
    (8 1 0.6)
    (0 1 0.6)
    (20 1 0.6)
    (20 0.5 0.6)
    (20 0 0.6)
    (20 -1 0.6)
    (8 -1 0.6)
    
);

blocks
(
    hex (0 1 2 3 11 12 13 14) (80 10 1) simpleGrading (1 1 1)
    hex (3 2 4 5 14 13 15 16) (80 10 1) simpleGrading (1 1 1)
    hex (2 7 6 4 13 18 17 15) (120 10 1) simpleGrading (1 1 1)
    hex (1 8 7 2 12 19 18 13) (120 10 1) simpleGrading (1 1 1)
    hex (10 9 8 1 21 20 19 12) (120 20 1) simpleGrading (1 1 1)
);

edges
(
);

boundary
(
    inlet
    {
        type patch;
        faces
        (
            (0 11 14 3)
            (3 14 16 5)
        );
    }
    outlet
    {
        type patch;
        faces
        (
            (9 8 19 20)
            (8 7 18 19)
            (7 6 17 18)
        );
    }
    frontAndBack
    {
        type empty;
        faces
        (
            (0 3 2 1)
            (11 12 13 14)
            (3 5 4 2)
            (13 15 16 14)
            (2 4 6 7)
            (13 18 17 15)
            (1 2 7 8)
            (12 19 18 13)
            (10 1 8 9)
            (21 20 19 12)
        );
    }
    
    noslipwall
    {
        type wall;
        faces
        (
            (4 5 16 15)
            (4 15 17 6)
            (0 1 12 11)
            (9 20 21 10)
            (1 10 21 12)
            
         );
         }   
            
);

mergePatchPairs
(
);

// ************************************************************************* //

with applyinf the grading factor 0.2

/*--------------------------------*- C++ -*----------------------------------*\
  =========                 |
  \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
   \\    /   O peration     | Website:  https://openfoam.org
    \\  /    A nd           | Version:  9
     \\/     M anipulation  |
\*---------------------------------------------------------------------------*/
FoamFile
{
    format      ascii;
    class       dictionary;
    object      blockMeshDict;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

convertToMeters 0.01;

vertices
(
    (0 0 0)
    (8 0 0)
    (8 0.5 0)
    (0 0.5 0)
    (8 1 0)
    (0 1 0)
    (20 1 0)
    (20 0.5 0)
    (20 0 0)
    (20 -1 0)
    (8 -1 0)
    
    (0 0 0.6)
    (8 0 0.6)
    (8 0.5 0.6)
    (0 0.5 0.6)
    (8 1 0.6)
    (0 1 0.6)
    (20 1 0.6)
    (20 0.5 0.6)
    (20 0 0.6)
    (20 -1 0.6)
    (8 -1 0.6)
    
);

blocks
(
    hex (0 1 2 3 11 12 13 14) (80 10 1) simpleGrading (0.2 5 1)
    hex (3 2 4 5 14 13 15 16) (80 10 1) simpleGrading (0.2 0.2 1)
    hex (2 7 6 4 13 18 17 15) (120 10 1) simpleGrading (5 0.2 1)
    hex (1 8 7 2 12 19 18 13) (120 10 1) simpleGrading (5 5 1)
    hex (10 9 8 1 21 20 19 12) (120 20 1) simpleGrading (5 5 1)
);

edges
(
);

boundary
(
    inlet
    {
        type patch;
        faces
        (
            (0 11 14 3)
            (3 14 16 5)
        );
    }
    outlet
    {
        type patch;
        faces
        (
            (9 8 19 20)
            (8 7 18 19)
            (7 6 17 18)
        );
    }
    frontAndBack
    {
        type empty;
        faces
        (
            (0 3 2 1)
            (11 12 13 14)
            (3 5 4 2)
            (13 15 16 14)
            (2 4 6 7)
            (13 18 17 15)
            (1 2 7 8)
            (12 19 18 13)
            (10 1 8 9)
            (21 20 19 12)
        );
    }
    
    noslipwall
    {
        type wall;
        faces
        (
            (4 5 16 15)
            (4 15 17 6)
            (0 1 12 11)
            (9 20 21 10)
            (1 10 21 12)
            
         );
         }   
            
);

mergePatchPairs
(
);

// ************************************************************************* //

CONTROLDICT

/*--------------------------------*- C++ -*----------------------------------*\
  =========                 |
  \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
   \\    /   O peration     | Website:  https://openfoam.org
    \\  /    A nd           | Version:  9
     \\/     M anipulation  |
\*---------------------------------------------------------------------------*/
FoamFile
{
    format      ascii;
    class       dictionary;
    location    "system";
    object      controlDict;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

application     icoFoam;

startFrom       startTime;

startTime       0;

stopAt          endTime;

endTime         3;

deltaT          1e-3;

writeControl    runTime;

writeInterval   0.2;

purgeWrite      0;

writeFormat     ascii;

writePrecision  6;

writeCompression off;

timeFormat      general;

timePrecision   6;

runTimeModifiable true;


// ************************************************************************* //

PRESSURE FILE

/*--------------------------------*- C++ -*----------------------------------*\
  =========                 |
  \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
   \\    /   O peration     | Website:  https://openfoam.org
    \\  /    A nd           | Version:  9
     \\/     M anipulation  |
\*---------------------------------------------------------------------------*/
FoamFile
{
    format      ascii;
    class       volScalarField;
    object      p;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

dimensions      [0 2 -2 0 0 0 0];

internalField   uniform 0;

boundaryField
{
    inlet
    {
        type            zeroGradient;
    }

    outlet
    {
        type            fixedValue;
        value            uniform 0;
    }

    frontAndBack
    {
        type            empty;
    }
    noslipwall
    {
        type            zeroGradient;
    }
        
}

// ************************************************************************* //

VELOCITY FILE

/*--------------------------------*- C++ -*----------------------------------*\
  =========                 |
  \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
   \\    /   O peration     | Website:  https://openfoam.org
    \\  /    A nd           | Version:  9
     \\/     M anipulation  |
\*---------------------------------------------------------------------------*/
FoamFile
{
    format      ascii;
    class       volVectorField;
    object      U;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

dimensions      [0 1 -1 0 0 0 0];

internalField   uniform (0 0 0);

boundaryField
{
    inlet
    {
        type            fixedValue;
        value           uniform (0.066 0 0);
    }

    outlet
    {
        type            zeroGradient;
    }

    frontAndBack
    {
        type            empty;
    }
    noslipwall
    {
        type            noSlip;
     }     
}

// ************************************************************************* //

 TRANSPORTPROPERTIES

/*--------------------------------*- C++ -*----------------------------------*\
  =========                 |
  \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
   \\    /   O peration     | Website:  https://openfoam.org
    \\  /    A nd           | Version:  9
     \\/     M anipulation  |
\*---------------------------------------------------------------------------*/
FoamFile
{
    format      ascii;
    class       dictionary;
    location    "constant";
    object      transportProperties;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

nu              [0 2 -1 0 0 0 0] 1e-4;


// ************************************************************************* //

OUT PUT

WITH OUT APPLYING ANY GRADING FACTOR THE BLOCKMESH

THE VELOCITY DIAGRAM WITH OUT APPLYING THE GRADING FACTOR

THE VELOCITY DIAGRAM WITH GRADING FACTOR 0.2

THE PRESSURE FLOW DIAGRAM WITH OUT APPLYING THE GRADING FACTOR

THE PRESSURE FLOW DIAGRAM WITH GRADING FACTOR 0.2

THE PLOT FOR THE VELOCITY AT 0.085 WITH OUT APPLYING THE GRADING FACTOR

THE PLOT FOR THE VELOCITY AT 0.085 WITH APPLYING THE GRADING FACTOR 0.2

CONCLUSION

Here by changing the simple mgrading factor from 0.2 to 1 the mesh become finer and the solution become accurate

over all the change in size of simplw grading factor the result remain the same as approximately.

execution time is lower for lower messhing grading factor.