CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > OpenFOAM Programming & Development

reactingFoam fvOption ignition

Register Blogs Members List Search Today's Posts Mark Forums Read

Like Tree2Likes
  • 2 Post By khalifa

Reply
 
LinkBack Thread Tools Display Modes
Old   September 20, 2015, 21:03
Default reactingFoam fvOption ignition
  #1
New Member
 
Join Date: Apr 2015
Posts: 25
Rep Power: 3
khalifa is on a distinguished road
Hello dear Foamers,

I am simulating 1-d premixed laminar flame with reactingFoam and need to ignite the process using fvOption file. I need to set the ignition strength of 5 e9 J/m3Ěs for 0.0002 s. how can I translate these paramters to fvOption file ?

Thanks
khalifa is offline   Reply With Quote

Old   September 25, 2015, 21:05
Question ignition parameters
  #2
New Member
 
kai wiseel
Join Date: Sep 2015
Posts: 4
Rep Power: 3
kaaaixx is on a distinguished road
Hello khalifa,

I am stucking nearly at the same point.. Did you find a answer of how the ignition parameters are linked to "the real" ignition energy?

Thanks in advance,
Kai
kaaaixx is offline   Reply With Quote

Old   September 30, 2015, 05:52
Default
  #3
New Member
 
Join Date: Apr 2015
Posts: 25
Rep Power: 3
khalifa is on a distinguished road
Quote:
Originally Posted by kaaaixx View Post
Hello khalifa,

I am stucking nearly at the same point.. Did you find a answer of how the ignition parameters are linked to "the real" ignition energy?

Thanks in advance,
Kai
Hello Kai,

actually I found this

Code:
-----------------------------*- C++ -*----------------------------------*\
| =========                 |                                                 |
| \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox           |
|  \\    /   O peration     | Version:  2.2.0                                 |
|   \\  /    A nd           | Web:      www.OpenFOAM.org                      |
|    \\/     M anipulation  |                                                 |
\*---------------------------------------------------------------------------*/
FoamFile
{
    version     2.0;
    format      ascii;
    class       dictionary;
    location    "system";
    object      fvOptions;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
source1
{
    type            fixedTemperatureConstraint;
    active          true;
    timeStart       1e-7;
    duration        1e-7;
    selectionMode   cellSet;
    cellSet         ignitionCells;

    fixedTemperatureConstraintCoeffs
    {
        mode            uniform;
        temperature     3000;
    }
}


/*energySource1
{
    type            scalarSemiImplicitSource;
    active          true;
    timeStart       0;
    duration        0.0002;
  selectionMode   cellSet; //cellSet // points //cellZone
    cellSet        ignitionCells;

    scalarSemiImplicitSourceCoeffs
    {
        volumeMode      absolute;
        injectionRateSuSp
        {
            h           (10 0);
        }
    }
}

but to be honest , both criteria (modifieng h or t) did not deliver reasonable results at the end. I mean , combustion occurred, but I think the energy equation was effected and the final temperature that I got is not really correct. in addition, I really dont know what is the unit of 10 in h (10 0); I just kept trying value until the mixture ignited without exceeding the 3000 k limit.

could you please try it and share your experience with it ?
khalifa is offline   Reply With Quote

Old   September 30, 2015, 06:00
Default
  #4
Senior Member
 
mkraposhin's Avatar
 
Matvey Kraposhin
Join Date: Mar 2009
Location: Moscow, Russian Federation
Posts: 330
Rep Power: 11
mkraposhin is on a distinguished road
Hi, if i'm right, then you want to insert energy source in energy equation.

You can do this with next two types of fvOption objects:
- SemiImplicitSource
- CodedSource
mkraposhin is offline   Reply With Quote

Old   September 30, 2015, 06:15
Default
  #5
New Member
 
Join Date: Apr 2015
Posts: 25
Rep Power: 3
khalifa is on a distinguished road
Quote:
Originally Posted by mkraposhin View Post
Hi, if i'm right, then you want to insert energy source in energy equation.

You can do this with next two types of fvOption objects:
- SemiImplicitSource
- CodedSource
Thank you for your kind response.

Actually this is what I am trying to do, and this is the energy source implementation in my fvOptions file

Code:
/*energySource1
{
    type            scalarSemiImplicitSource;
    active          true;
    timeStart       0;
    duration        0.0002;
  selectionMode   cellSet; //cellSet // points //cellZone
    cellSet        ignitionCells;

    scalarSemiImplicitSourceCoeffs
    {
        volumeMode      absolute;
        injectionRateSuSp
        {
            h           (10 0);
        }
    }
now if you colud please help me further, as I am still a beginner with openFoam, is it correct to specify h as the energy source ? wont it be confused with any other term of the energy equationo ? and secondly, do you know what is the 0 value stands for ?
khalifa is offline   Reply With Quote

Old   September 30, 2015, 06:37
Default
  #6
Senior Member
 
mkraposhin's Avatar
 
Matvey Kraposhin
Join Date: Mar 2009
Location: Moscow, Russian Federation
Posts: 330
Rep Power: 11
mkraposhin is on a distinguished road
Quote:
Originally Posted by khalifa View Post
Thank you for your kind response.

Actually this is what I am trying to do, and this is the energy source implementation in my fvOptions file

Code:
/*energySource1
{
    type            scalarSemiImplicitSource;
    active          true;
    timeStart       0;
    duration        0.0002;
  selectionMode   cellSet; //cellSet // points //cellZone
    cellSet        ignitionCells;

    scalarSemiImplicitSourceCoeffs
    {
        volumeMode      absolute;
        injectionRateSuSp
        {
            h           (10 0);
        }
    }
now if you colud please help me further, as I am still a beginner with openFoam, is it correct to specify h as the energy source ? wont it be confused with any other term of the energy equationo ? and secondly, do you know what is the 0 value stands for ?
Well, sorry, i didn't saw piece of code, related to energy.

So, you must select options as follows:
1. volumeMode should be changed from absolute to specific, because, as i see from starting post, your source have dims: J/m3/s
If you will leave volumeMode as absolute, then values of sources will be normalized by volume of cell sets, that you specified in cellSet.

2. h specifies only name for which balance equation is applied. energy equation can be applied both to specific internal energy (e) or specific enthalpy (h). You can check correct variable in file thermophysicalProperties:
energy sensibleEnthalpy; - that means, that you are solving energy equation with primary variable specific enthalpy
3. Values in brackets are sources:
- first value is an explicit source (Su), must be 5 e9 J/m3Ěs, but you specified 10 J/s
- second value is an implicit source (Sp), it will be substituted to equation of energy as follows: Dh/Dt = Sp*h

Last edited by mkraposhin; September 30, 2015 at 06:39. Reason: grammar
mkraposhin is offline   Reply With Quote

Old   September 30, 2015, 06:49
Default
  #7
New Member
 
Join Date: Apr 2015
Posts: 25
Rep Power: 3
khalifa is on a distinguished road
Quote:
Originally Posted by mkraposhin View Post
Well, sorry, i didn't saw piece of code, related to energy.

So, you must select options as follows:
1. volumeMode should be changed from absolute to specific, because, as i see from starting post, your source have dims: J/m3/s
If you will leave volumeMode as absolute, then values of sources will be normalized by volume of cell sets, that you specified in cellSet.

2. h specifies only name for which balance equation is applied. energy equation can be applied both to specific internal energy (e) or specific enthalpy (h). You can check correct variable in file thermophysicalProperties:
energy sensibleEnthalpy; - that means, that you are solving energy equation with primary variable specific enthalpy
3. Values in brackets are sources:
- first value is an explicit source (Su), must be 5 e9 J/m3Ěs, but you specified 10 J/s
- second value is an implicit source (Sp), it will be substituted to equation of energy as follows: Dh/Dt = Sp*h
Thank you alot.

this my thermophyiscalProperties related code

Quote:
thermoType
{
type hePsiThermo;
mixture reactingMixture;
transport sutherland;
thermo janaf;
energy sensibleEnthalpy;
equationOfState perfectGas;
specie specie;
}
so yes you are correct it uses sensibleEnthalpy. As far as I understood for what I should do , is to use this snesibleEnthalpy in the fvOptions file instead of h?

Code:
energySource1
{
    type            scalarSemiImplicitSource;
    active          true;
    timeStart       0;
    duration        0.0001;
  selectionMode   cellSet; //cellSet // points //cellZone
    cellSet        ignitionCells;

    scalarSemiImplicitSourceCoeffs
    {
        volumeMode      specific;
        injectionRateSuSp
        {
           h         (5e9 0);
        }
    }
}
Thanks again
khalifa is offline   Reply With Quote

Old   September 30, 2015, 06:52
Default
  #8
New Member
 
Join Date: Apr 2015
Posts: 25
Rep Power: 3
khalifa is on a distinguished road
Quote:
Originally Posted by khalifa View Post
Thank you alot.

this my thermophyiscalProperties related code



so yes you are correct it uses sensibleEnthalpy. As far as I understood for what I should do , is to use this snesibleEnthalpy in the fvOptions file instead of h?

Code:
energySource1
{
    type            scalarSemiImplicitSource;
    active          true;
    timeStart       0;
    duration        0.0001;
  selectionMode   cellSet; //cellSet // points //cellZone
    cellSet        ignitionCells;

    scalarSemiImplicitSourceCoeffs
    {
        volumeMode      specific;
        injectionRateSuSp
        {
           h          (5e9 0);
        }
    }
}
Thanks again

I guess I got it now, it should be kept h. and the solver will solve it for sensible enthalpy. sorry for the too many silly questions

I really appreciate your help . it works perfect
wayne14 and SH_Zhong like this.
khalifa is offline   Reply With Quote

Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
how to achieve ignition of premixed flame using ReactingFoam Dan1788 OpenFOAM Running, Solving & CFD 23 November 20, 2015 07:56
reactingFoam: ignition point? Jui OpenFOAM Running, Solving & CFD 8 September 9, 2014 15:50
Doubt in code ignition reactingFoam RCB123456 OpenFOAM Running, Solving & CFD 0 August 16, 2014 05:30
Ignition in reactingFoam pas32 OpenFOAM Programming & Development 4 August 13, 2014 09:00
Ignition point in reactingFoam? lfgmarc OpenFOAM Programming & Development 0 July 11, 2011 18:00


All times are GMT -4. The time now is 11:40.