Setting problem of the bubble induced turbulence in CFX

zhubohong · January 3, 2019, 11:32

Hello, guys, anyone can help me? My questions is as follows:
CFX has its own model (Sato model) to predict the bubble induced turbulence.
However, I want to use the another way to do it. That is modifing the source of k-e turbulence model accroding to Pfleger and Becker's work.
The equation can be found in attached figure.

So, My problem is how to add this equation in CFX, how to edit this equation?
For example, how to edit the item of total interphase force.

ghorrocks · January 4, 2019, 01:51

You can add extra equations as a turbulence source term. But you cannot edit the fundamental turbulence equations.

zhubohong · January 4, 2019, 02:02

Quote:

Originally Posted by ghorrocks

You can add extra equations as a turbulence source term. But you cannot edit the fundamental turbulence equations.

Thanks for your reply.
Currently, the major problem for me is how to edit the attacted equation in CFX expression.

For example, the attacted equation is a function of total interphase force, I don't know how to edit it in expression. I checked the "ANSYS CFX reference Guide", but I still find a sovled method.

ghorrocks · January 4, 2019, 02:08

The equation was not attached. Please post the attachment again.

zhubohong · January 4, 2019, 02:20

Quote:

Originally Posted by ghorrocks

The equation was not attached. Please post the attachment again.

Please check the attached figure. Just add these two equations in the source of k-e turbulence model.
The equations come from the reference"D.Zhang et al. Chem. Eng. Sci., 2006, 61, 7593"

ghorrocks · January 4, 2019, 05:51

Defining the terms might help...... What is S_K,BIT and S_E,BIT?

zhubohong · January 4, 2019, 06:06

Quote:

Originally Posted by ghorrocks

Defining the terms might help...... What is S_K,BIT and S_E,BIT?

Sorry for this, please check the new attached figure. Thanks

ghorrocks · January 5, 2019, 05:24

They appear to be just source terms on the k and e equations. So just add them as a source term.

zhubohong · January 5, 2019, 06:11

Quote:

Originally Posted by ghorrocks

They appear to be just source terms on the k and e equations. So just add them as a source term.

I got the point. Thanks. By the way, is it added a sub-domain for introducing the equation?

ghorrocks · January 5, 2019, 17:07

Yes, you apply source terms in sub-domains. Sub-domains can be the whole domain if you like.

zhubohong · January 6, 2019, 08:23

Quote:

Originally Posted by ghorrocks

Yes, you apply source terms in sub-domains. Sub-domains can be the whole domain if you like.

Thanks, the attched figure shows my new question. May you give me some tips?

ghorrocks · January 6, 2019, 17:46

Yes, your Argon to Liquid relative velocity vector is a vector (obviously), and the k source term must evaluate to a scalar field (obviously, k is a scalar field). So you are going to have to convert your vector to a scalar somehow. You are going to have to determine the appropriate way to do that as there are many ways. The reference you got this function from will probably tell you how to do it.

The most obvious thing is to take the magnitude of the relative velocity vector, but this might not be correct so it is up to you to choose the best method.

January 3, 2019, 11:32	Setting problem of the bubble induced turbulence in CFX	#1
zhubohong Member zhubohong Join Date: Apr 2018 Posts: 37 Rep Power: 8	Hello, guys, anyone can help me? My questions is as follows: CFX has its own model (Sato model) to predict the bubble induced turbulence. However, I want to use the another way to do it. That is modifing the source of k-e turbulence model accroding to Pfleger and Becker's work. The equation can be found in attached figure. So, My problem is how to add this equation in CFX, how to edit this equation? For example, how to edit the item of total interphase force.

January 4, 2019, 01:51		#2
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,729 Rep Power: 143	You can add extra equations as a turbulence source term. But you cannot edit the fundamental turbulence equations. __________________ Note: I do not answer CFD questions by PM. CFD questions should be posted on the forum.

January 4, 2019, 02:08		#4
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,729 Rep Power: 143	The equation was not attached. Please post the attachment again. __________________ Note: I do not answer CFD questions by PM. CFD questions should be posted on the forum.

January 4, 2019, 05:51		#6
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,729 Rep Power: 143	Defining the terms might help...... What is S_K,BIT and S_E,BIT? __________________ Note: I do not answer CFD questions by PM. CFD questions should be posted on the forum.

January 5, 2019, 05:24		#8
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,729 Rep Power: 143	They appear to be just source terms on the k and e equations. So just add them as a source term. __________________ Note: I do not answer CFD questions by PM. CFD questions should be posted on the forum.

January 5, 2019, 17:07		#10
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,729 Rep Power: 143	Yes, you apply source terms in sub-domains. Sub-domains can be the whole domain if you like. __________________ Note: I do not answer CFD questions by PM. CFD questions should be posted on the forum.

January 6, 2019, 17:46		#12
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,729 Rep Power: 143	Yes, your Argon to Liquid relative velocity vector is a vector (obviously), and the k source term must evaluate to a scalar field (obviously, k is a scalar field). So you are going to have to convert your vector to a scalar somehow. You are going to have to determine the appropriate way to do that as there are many ways. The reference you got this function from will probably tell you how to do it. The most obvious thing is to take the magnitude of the relative velocity vector, but this might not be correct so it is up to you to choose the best method. __________________ Note: I do not answer CFD questions by PM. CFD questions should be posted on the forum.

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