In solver theory guide the continuity equation is set to be equal to 0, but in some papers related to the phenomena I want to model, the continuity equation is set to be equal to a mass source term.
Dear Lucas,
Usually in Fluent ansys we can define a macro for source which can be incooparated using a UDF.
Ok, your question was rather about ANSYS CFX, instead of ANSYS Fluent.
In ANSYS CFX you can add a mass source/sink term to the continuity equation, if you previously define a subdomain. The subdomain can be identical to the full fluid domain as well. Than, either by an expression or an additional variable, you can define a source term for any solved equation in ANSYS CFX.
Please have in mind, that it helps to propperly linearize the source term. Otherwise the convergence behavior of the solver might be deteriorated by this source term, depending upon the stength and sign of it.
Regards,
Dr. Th. Frank.
Thomas Frank, Thank you very much for your reply.
I followed your instructions, but since my fluid is a pair of gases and only one component is adsorbed by a porous medium. In the settings of Sources (in the subdomain I created) I can only add the source term to the continuity and it seems that I am adding the source term to the global continuity equation. Is there a way to add a source to the continuity equation for just one component of my fluid?
If you have a homogeneous mixture of two gases, than only one continuity equation for the mixture is solved. Instead you should be able to add a source/sink term to the mixture fraction transport equation for the species of your mixture, which is actually not the "constraint" component.
Thomas Frank, thanks for the quick reply. The mixture is homogeneous. When you say that I " should be able to add a source/sink term to the mixture fraction transport equation for the species of your mixture", you mean the mass fraction option that appears in the settings of Sources that appears in the subdomain section?
Can I add the continuity source term to the specific specie that are adsorbed via FORTRAN? I am reading CFX documentation but so far, I haven't got any answers to my doubts.
Yes, I think so. Maybe it is not documented in the publically available documentation, because it is a rather special topic. But it should be possible. The sink term could be specified in CCL as well, if the numerical recipe could be formulated in CCL language terms.
For the expression ΔT/Δy= -Rate×Enthalpy/λ some authors used -Rate×Enthalpy as Flux (makes sense as we just taking λ to LHS of equation) and some used T_wall=((-Rate×Enthalpy) Δy/λ)+T_fluid where ΔT=T_wall - T_fluid I guess T_fluid is T in ANSYS CFX-Pre. But how can I determine Δy which I think is distance between boundary cells and boundary? For now I am just taking 300th of channel height.
Also, how can I apply (in CFX Pre) T_wall as it is a variable temperature?
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