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John August 24, 2005 18:56

'Surface Sources'
 
Hi,all,

In CFX, we can define point sources. I was wondering if it is also possible to define 'surface sources'?

I think about this because I try to find an alternative way to define the multiple gas inlets for a gas-liquid problem. Thus the geometry building up and meshing may be much easier.....

Any idea about this?

Thanks in advance!

John


Rui August 24, 2005 20:21

Re: 'Surface Sources'
 
Hi,

<u>In CFX-10</u> (the new version already available for download) <u>it's now possible to define boundary mass sources</u>.

In CFX-5.7 and 5.7.1 it was possible to define boundary sources only for scalar equations, and boundary mass sources were not included. These boundary sources had to be specified by editing the .ccl file. Take a look at the CFX-5.7 or 5.7.1 documentation (Solver Modelling, Basic Capabilities Modelling, Sources, Boundary Sources)

Regards,

Rui

John August 24, 2005 23:26

Re: 'Surface Sources'
 
Thanks Rui for you comment. It helps a lot to me.

What I exactly want to do is that, I want to define a face in cfx-pre similar as defining a source point source. Then define a source(ie. mass+momentum+additional variables sources) on this face(or faces). This face should not be a predefined boundary and can be at any locations in the domain.

In another word, I want to define gas inlets with sources, instead of defining boundary conditions.

Is it possible to do this in CFX10 or CFX5.7.1?

Best regards!

John

Rui August 25, 2005 18:28

Re: 'Surface Sources'
 
Hi,

You cannot define boundary mass neither momentum sources in CFX-5.7.1. In CFX-10 you can.

I still haven't worked with boundary sources, but I'm sure you have to associate a boundary source to a boundary.

For what I understood from your first post, you have a wall with many gas inlets, and you don't want to define these inlet locations as surfaces. If you don't define them as surfaces you cannot define them as boundaries in Pre. But if you have not defined the inlet loacations as boundaries you cannot define boundary sources there.

The only way I can see to do what you want is by defining boundary sources for the whole wall, and defining the sources as expressions (probably making use of step functions) so they are zero outside the inlet locations.

But remember that when you are specifying a momentum source you are not specifying the velocity, you are specifying a force per unit volume (volume source) or per unit area (boundary source).When you specify a mass source you have automatically to specify the velocity, so this would be enough to "create" an inlet. But I think you should contact CFX support and ask them what they think about your idea. I don't know how CFX will manage the case when you a have a no-slip wall (velocity=0) together with a mass source (velocity=U).

I'm sorry if I haven't helped very much.

Regards,

Rui

Rui August 25, 2005 19:42

Re: 'Surface Sources'
 
Hi,

I checked the CFX-10 documentation, and boundary momentum sources are not included in CFX-10.However, as I said, you don't need boundary momentum sources to "create" an inlet

http://www-waterloo.ansys.com/downlo...FXMod.book.pdf , page 39

Neale August 25, 2005 23:49

Re: 'Surface Sources'
 
Boundary sources in CFX 10 must be applied to a pre-existing boundary condition.

In the GUI the types of boundary conditions are restricted to walls and interfaces.

Boundary sources can be applied on other boundary types as well but this is a CCL only feature.

Neale.

John August 25, 2005 23:51

Re: 'Surface Sources'
 
Thanks a lot, Rui. Your comments do open my mind. I will take a look at the new version's help file and see if it worth to do this way.

Best regards!

John



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