reactingFoam with variable diffusivity
 

Hi nakul,

thanks for your posts.
could you please send me some information about implementing reactingFoam with variable diffusivity. I am Modeling methane turbulent flame and in part of my research I want to assess Variable diffusivity effect on my results.

sincerely yours

Hi

Implementing the feature of variable diffusivity right from the scratch may be quite long and difficult. But I think that you may find some thing on the net in this regard. I haven't checked but if you come across something do post it here. Stuff you may find on net may not be even for reactingFoam but you would get an idea of editing existing thermodynamic models which is the fundamental way of implementing variable diffusivity.

Alternatively you may assume a constant value for Lewis no. and multiply it with alpha which can be "variable" in OF. This way you would be able to have variable diffusivity in a much simpler way as far as reactingFoam is concerned.

-Nakul

XiFoam output files
 

As a continuation of the previous discussion regarding calculation of temperature when using XiFoam. I am quite new to OpenFoam and as per my understanding, please correct if I am mistaken, for each file in the 0 directory there is an associated IOobject contained within the code.

For example within the /0 folder in the XiFoam tutorial there are the files: alphat, b, epsilon, k, mut, p, Su, T, Tu, U, Xi

Therefore it is my understanding that within the code there is an IOoject for each of these parameters.

For example within createFields.H of the XiFoam solver (contained in applications/solvers/combustion/XiFoam) we have:

volvectorField U
(
IOobject
(
“U”,
runtime.timeName(),
mesh,
IOobject::MUST_READ,
IOobject::AUTO_WRITE
),
mesh
);

I have been able to track down the associated IOobject for each of the parameters which are saved to file apart from b, p and T.

I notice in createFields.H, there is:

volScalarField& p = thermo.p();

and

volScalarField& b = composition.Y(“b”);

and in previous releases of OpenFoam, createFields.H also contained: const volScalarField& T = thermo.T();

Can you please comment on how/where b, p and T are calculated and saved to file and where their associated IOobject, if it exists, is located.

Many thanks,

James

Calculate Temperature in hhuMixtureThermo
 

Hi Ehsan your post was very helpful but I've a doubt about temperature calculation in library hhuMixtureThermo.C; I'd like to ask you if temperature is calculated with TH() function or based on Tb and Tu using products and reactans JANAF coefficients i.e.
T= Tu(b) + Tb(1-b).
Thanks in advance, Vito

Hallo,

I'm working with XiFoam and I have the same understanding problem about calculating T.
In XiFoam there is an equation for "h" which I'm pretty sure Its the total enthalpy, so that means for an adiabatic case it would not be used.

In my understanding, theoretically If we have the adiabatic temperature of the flame we can calculate the tempreture as function of "b" every where.
I can imagine that we can find out the adiabatic temperature using formation enthalpy of reactant and product and the "cp" and "mass fraction" of fuel.

I could not see the links that nakul sent, and its still an open question for me.
It would be very nice if you guys could help me to understand that.


thx

XiFoam-Hydrogen
 

Hi guys,

I was using rhoreactingFoam for ddt of Hydrogen, and now I want to switch to the XiFoam. Can you please tell me how can I have the Hydrogen properties and coefficients for simulating Hydrogen DDT?
Moreover, I used to set high temperature circle for ignition in setFields, can you please tell me whether I can use the same way or no I should use the ignition in combustion properties?

Cheers,
Reza