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enigma July 14, 2010 20:55

Chemical Equilibrium Simulation using Fluent
G'day Gentlemen,

Iíd kindly like to ask you if you could assist here as I unfortunately havenít been able to figure out a solution myself yet. Iíd like to do a chemical equilibrium simulation using Fluent. Iím using AIR as test gas and do not want to split it up into its individual components (N2, O2), but want to run the simulation with one species (equilibrium AIR). Equilibrium AIR changes its properties with temperature. For chemical equilibrium calculations one requires all the following parameters to be functions of temperature:

-Specific heat capacity
-Molecular weight

I calculated the equilibrium air parameters, however, canít get Fluent to accept a variable molecular weight. The molecular weight changes due to dissociation of the gas at higher temperatures. I have written my own material database (.scm file) where molecular weight is specified as a function of temperature, however, when I want to use that species Fluent says that it cannot accept a variable molecular mass.

Can you think of a solution how to implement a variable molecular mass?

Thank you for your help!

ian.maes October 21, 2011 05:05

Same problem

Although this post is from two years ago and there have been no replies, I hope to get an answer to the above-mentioned question.

I have the similar problem in defining a user-defined molecular weight (in my case for argon and water). This is necessary to capture the influence of dissociation and ionization at high temperatures on the molecular weight.

Did you find a solution to this problem, Enigma (or anybody else)?

thank you in advance,


chor October 27, 2011 08:02

I did not find anything either

I could affirm that I am a serious fluent user (10 years), and I have found this problem 4 years ago. I did almost everything imaginable to implement equilibrium air, but was impossible to cope with the molecular weight problem.

I have also contacted fluent experts in combustion by that time, and they could not give me a feasible awnser (for the density solver). For the pressure based solver you can always try to deactivate species transport and manage to put the species you want. But this not very usefull for high mach number.

So ye, I am anxious to see If somebody did it. I took it personal...


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