[zyzz]

Hi everyone,

I am trying to solve a problem regarding species transport without reactions. So I've turned on the species transport model and made my mixture material.

For my mixture properties I have:

• Density = ideal-gas
• Cp = mixing-law
• Thermal conductivity = ideal-gas-mixing-law
• Viscosity = ideal-gas-mixing-law

For each of the fluid materials that comprise the mixture I have:

• Cp = kinetic-theory
• Thermal conductivity = kinetic-theory
• Viscosity = kinetic-theory
• Note: there's no option to edit density, which I assume is due to the mixture density selected as ideal-gas

According to the user guide, this should be ok:
https://www.sharcnet.ca/Software/Ans...p_mixture.html

"Define the specific heat capacity for each of the fluid materials that comprise the mixture. You may define constant or (if applicable) temperature-dependent heat capacities for the individual species. You may also use kinetic theory for the individual heat capacities, if applicable."

However, when I ran the simulation, before every iteration, it says "Warning: Incorrect Specific Heat value" literally over 200 times.

If it is relevant, I am using the Pressure-Based Solver, solving the energy, standard k-e and species transport models with the coupled pressure-velocity coupling scheme. I am also using Fluent 18.0

Thanks for reading

[LuckyTran]

Honestly I don't see anything wrong with what you're doing. But when you select kinetic theory for transport properties, you must input give the Lennard-Jones parameters and degrees of freedom. Did you do this?

Originally Posted by zyzz

• Note: there's no option to edit density, which I assume is due to the mixture density selected as ideal-gas

That's correct. You selected ideal-gas so the density is calculated from the Molecular weight. The molecular weight user input plays the role of a user input for density.

[zyzz]

Originally Posted by LuckyTran

Honestly I don't see anything wrong with what you're doing. But when you select kinetic theory for transport properties, you must input give the Lennard-Jones parameters and degrees of freedom. Did you do this?

Thanks for your reply LuckyTran. I didnt change the L-J parameters or degrees of freedom for any material because all my materials were selected from the Fluent database. So by default, they already had values for the kinetic theory inputs (although degrees of freedom = 0 for every material).

[Muneeb]

Originally Posted by zyzz

Hi everyone,

I am trying to solve a problem regarding species transport without reactions. So I've turned on the species transport model and made my mixture material.

For my mixture properties I have:

• Density = ideal-gas
• Cp = mixing-law
• Thermal conductivity = ideal-gas-mixing-law
• Viscosity = ideal-gas-mixing-law

For each of the fluid materials that comprise the mixture I have:

• Cp = kinetic-theory
• Thermal conductivity = kinetic-theory
• Viscosity = kinetic-theory
• Note: there's no option to edit density, which I assume is due to the mixture density selected as ideal-gas

According to the user guide, this should be ok:
https://www.sharcnet.ca/Software/Ans...p_mixture.html

"Define the specific heat capacity for each of the fluid materials that comprise the mixture. You may define constant or (if applicable) temperature-dependent heat capacities for the individual species. You may also use kinetic theory for the individual heat capacities, if applicable."

However, when I ran the simulation, before every iteration, it says "Warning: Incorrect Specific Heat value" literally over 200 times.

If it is relevant, I am using the Pressure-Based Solver, solving the energy, standard k-e and species transport models with the coupled pressure-velocity coupling scheme. I am also using Fluent 18.0

Thanks for reading

Dear Marco Seid

I am encountering the same problem as you mentioned.
did you able to overcome the said problem?

[zyzz]

Originally Posted by Muneeb

Dear Marco Seid

I am encountering the same problem as you mentioned.
did you able to overcome the said problem?

Hi Muneeb,

Yes I did. The Cp value of each material should be piecewise-polynomial instead of kinetic theory.

Hope that helps.

[D.W.]

Hello,
You will get the message "Warning: Incorrect Specific Heat value" when you choose Cp : kinetic-theory if you leave the degrees of freedom = 0.
If you set degrees of freedom for air to 5, for example, then the message "Warning: Incorrect Specific Heat value" disappears.
In this case, cp would equal cp=1/2*(8.314/28.966e-3)*(5+2)=1004.6 J/(kg*K).

-DW