[Manideep304]

Hello,

I have been working with XiFoam solver for a simulating a combustion process. I wanted to know how the strength value in Combustion properties is used exactly in the simulation. I have gone through few threads in the forums regarding this issue but could not find the answer. I am assuming that the strength value is used in the Energy equation but I do not know exactly how. If anyone has an answer, kindly do reply. Thank you in advance.

[dlahaye]

What is "strenght" here?

Energy equation used by XiFoma (EaEqn.H) is here:

https://github.com/OpenFOAM/OpenFOAM...XiFoam/EaEqn.H

[Manideep304]

In the combustion properties of XiFoam solver, we need to define the ignition properties such as diameter of ignition, duration of ignition, and strength of ignition.

Beqn is written as......
bEqn = beqn + ((strength * cellVolume * rhou) / duration ) / (b[ignSite] + 0.001)

Where bEqn is the flame propagation. When I try to determine the units of strength, i get s/kg

I find this strength term difficult to understand? Kindly comment if anyone knows the answer.

[casseer15]

Originally Posted by Manideep304

In the combustion properties of XiFoam solver, we need to define the ignition properties such as diameter of ignition, duration of ignition, and strength of ignition.

Beqn is written as......
bEqn = beqn + ((strength * cellVolume * rhou) / duration ) / (b[ignSite] + 0.001)

Where bEqn is the flame propagation. When I try to determine the units of strength, i get s/kg

I find this strength term difficult to understand? Kindly comment if anyone knows the answer.

This is an old thread, But I will provide an answer as per my understanding for anyone else who might be having similar problem. I too had great trouble understanding XiFoam (I still haven't understood) due to the lack of documentation, so would like to help anyone starting to use this.



BEqn is the transport equation of regress variable 'b' in XiFoam (Weller Model).

B Equation is actually

fvm::ddt(rho, b) + mvConvection->fvmDiv(phi, b) + fvm::div(phiSt, b) - fvm::Sp(fvc::div(phiSt), b) - fvm::laplacian(thermophysicalTransport->alphaEff(), b)
== fvModels.source(rho, b)

For the exact equation, refer H. G. Weller, "Development of a New Flame Area Combsution Model Using Conditional Averaging," Department of Mechanical Engineerig, Imperial College of Science Technology and Medicine, 1993.


Strength parameter is used in the ignition process, to start the reaction. At the ignition, the BEqn is modified as
bEqn = beqn + ((strength * cellVolume * rhou) / duration ) / (b[ignSite] + 0.001)


This sort of starts the combustion, (by injecting a value less that one to b), which then propagates as per the transport equation for b.

strength, location and duration basically specifies the ignition.