Mesh deformation & Porous Domain

Pled · July 10, 2018, 04:39

Hello everyone,

how can I model a porous domain to be able for mesh deformation?

ghorrocks · July 14, 2018, 08:17

Do porous domains not allow you to have mesh motion? I can understand why - it will introduce all sorts of new physics which you don't get otherwise. For instance, think about squeezing a wet sponge - it squeezes all the water out. This is new physics which you don't get in stationary meshes.

So if it is not allowed, it is for good reason.

If you still want to have a porous moving mesh domain: The porous domain is simply a source term added to the momentum equation. You can simply add this source term yourself to a moving mesh domain. Of course, if you do this, it is entirely up to you to ensure the model is appropriate, suitable and secondary effects are adequately handled.

Pled · July 18, 2018, 05:53

Thank you,
I agree that it will introduce new porous features and fluid ejection out of it, but still I need to model all of these.

But, how can I relate a momentum source with the porosity that I am aware of? Is there any bibliography that you know, or a cfx manual special for this?

ghorrocks · July 18, 2018, 07:24

When you add models on top of each other (eg porous + moving mesh) you get lots of high order terms in the equations. CFX does not have these high order terms. If you want to include these high order terms you will probably need to derive these high order terms and write your own solver.

If you can convince yourself the high order terms are not significant you can implement it in CFX. The CFX theory manual gives the equations used in the built it porous models, you just have to implement those as your own source terms.

July 10, 2018, 04:39	Mesh deformation & Porous Domain	#1
Pled Member Dimitrios S. P. Join Date: Jan 2018 Posts: 63 Rep Power: 8	Hello everyone, how can I model a porous domain to be able for mesh deformation?

July 14, 2018, 08:17		#2
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,870 Rep Power: 144	Do porous domains not allow you to have mesh motion? I can understand why - it will introduce all sorts of new physics which you don't get otherwise. For instance, think about squeezing a wet sponge - it squeezes all the water out. This is new physics which you don't get in stationary meshes. So if it is not allowed, it is for good reason. If you still want to have a porous moving mesh domain: The porous domain is simply a source term added to the momentum equation. You can simply add this source term yourself to a moving mesh domain. Of course, if you do this, it is entirely up to you to ensure the model is appropriate, suitable and secondary effects are adequately handled. __________________ Note: I do not answer CFD questions by PM. CFD questions should be posted on the forum.

July 18, 2018, 07:24		#4
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,870 Rep Power: 144	When you add models on top of each other (eg porous + moving mesh) you get lots of high order terms in the equations. CFX does not have these high order terms. If you want to include these high order terms you will probably need to derive these high order terms and write your own solver. If you can convince yourself the high order terms are not significant you can implement it in CFX. The CFX theory manual gives the equations used in the built it porous models, you just have to implement those as your own source terms. __________________ Note: I do not answer CFD questions by PM. CFD questions should be posted on the forum.

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July 18, 2018, 05:53		#3
Pled Member Dimitrios S. P. Join Date: Jan 2018 Posts: 63 Rep Power: 8	Thank you, I agree that it will introduce new porous features and fluid ejection out of it, but still I need to model all of these. But, how can I relate a momentum source with the porosity that I am aware of? Is there any bibliography that you know, or a cfx manual special for this?