[Hamilton]

Dear friends,
I have a question about Variable Composition Mixture (VCM) model. The composition of phases in this method (VCM) how can be changed ? In fact I simulated a flow containing two phase with different molar mass in a rotating geometry but the composition of phases did not change.

Regards

[ghorrocks]

It can be changed by interaction with fluid with a different composition (then you will get convection and diffusion effects), source terms and phase change.

How can you have two phases with different molar masses? Can you explain that please?

[Hamilton]

Dear Glenn
In fact I have prepared a new material using Variable Composition Mixture model which is contained two gases with different molar mass. The geometry is rotating and I expected that the gases be separated from each other due to centrifugal force but it is not occurred.

Regards

[Hamilton]

Originally Posted by ghorrocks

It can be changed by interaction with fluid with a different composition (then you will get convection and diffusion effects), source terms and phase change.

How can you have two phases with different molar masses? Can you explain that please?

Dear Glenn
In fact I have prepared a new material using Variable Composition Mixture model which is contained two gases with different molar mass. The geometry is rotating and I expected that the gases be separated from each other due to centrifugal force but it is not occurred.

Regards

[Opaque]

Dear Hamilton,

Separation of species within a multicomponent fluid due to pressure gradient cannot be modeled using ANSYS CFX. If you look at the documentation for the transport equation for species, you will see that there is no "pressure diffusion" contribution included in the species mass flux.

You can find the details of the pressure diffusion contribution in transport phenomena books such as Stewart, Bird and Lighfoot's book ( http://en.wikipedia.org/wiki/Transport_Phenomena_(book) ). There are some copies on the Internet such as:

http://www.icheh.com/Files/Posts/Por...2ed-part-2.pdf

See page 769, Eqn 24-2-8.

or the following presentation by Pietro Asinari ( http://staff.polito.it/pietro.asinar...Part1_v1.5.PDF )

See slide 33.

Hope the above helps

[Hamilton]

Originally Posted by Opaque

Dear Hamilton,

Separation of species within a multicomponent fluid due to pressure gradient cannot be modeled using ANSYS CFX. If you look at the documentation for the transport equation for species, you will see that there is no "pressure diffusion" contribution included in the species mass flux.

You can find the details of the pressure diffusion contribution in transport phenomena books such as Stewart, Bird and Lighfoot's book ( http://en.wikipedia.org/wiki/Transport_Phenomena_(book) ). There are some copies on the Internet such as:

http://www.icheh.com/Files/Posts/Por...2ed-part-2.pdf

See page 769, Eqn 24-2-8.

or the following presentation by Pietro Asinari ( http://staff.polito.it/pietro.asinar...Part1_v1.5.PDF )

See slide 33.

Hope the above helps

Dear Opaque,
Thank you very much for very good guidance, sorry for consuming your time, let me ask you two questions:
1- Is it possible to add a subroutine to CFX for containing the centrifugal force? (solving the modified transport equation)
2- Do you know the other CFD software such as FLUENT has this limitation or not? I mean does fluent contain the centrifugal force term in the transport equation?

Regards

[Antanas]

Originally Posted by Hamilton

Dear Opaque,
Thank you very much for very good guidance, sorry for consuming your time, let me ask you two questions:
1- Is it possible to add a subroutine to CFX for containing the centrifugal force? (solving the modified transport equation)
2- Do you know the other CFD software such as FLUENT has this limitation or not? I mean does fluent contain the centrifugal force term in the transport equation?

Regards

I'm interested in the same issues. Can anyone help?