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-   -   ANSYS CFX Tutorial 7 (http://www.cfd-online.com/Forums/cfx/26871-ansys-cfx-tutorial-7-a.html)

Sam January 6, 2009 19:32

ANSYS CFX Tutorial 7
 
Hi,

I am working through the tutorials ad have come to tute 7 whihc is the free surface flow over a 2d bump. This tutorial is very applicable to what i would liek to do my thesis on.

When I try to solve the problem I get an error message which reads, "The density-difference buoyancy model is being used, but the buoyancy reference density has not been specified"

I have tried loading the session file supplied but it also comes up with the error when I try to solve it

Has anyone had a similar problem or any advice on how to resolve the problem?

Regards,

Sam

Rogerio Fernandes Brito January 7, 2009 07:29

Re: ANSYS CFX Tutorial 7
 
I did some meshes of this case. IF YOU WANT TO use these grids...

http://www.4shared.com/file/65772301..._Mr_Brito.html

http://www.4shared.com/file/65770211..._Mr_Brito.html


Sam January 7, 2009 17:03

Re: ANSYS CFX Tutorial 7
 
Thayou I will have a play,

I am very much learning CFD and know quite little about the topic at this stage, I have read a few books Do you know of any other ways to better understand using CFD to generate free surface flows?

I feel the problem may be in the setting up of my problem rather than the meshing but I will try again.

Thanks again,

Sam

Glenn Horrocks January 7, 2009 18:34

Re: ANSYS CFX Tutorial 7
 
Hi,

I agree the problem likely to be the setup, not the mesh. The error message refers to the buoyancy reference density - have you set it as it requests?

What version of CFX are you using?

Glenn Horrocks

Sam January 7, 2009 19:03

Re: ANSYS CFX Tutorial 7
 
I am currently using v11

I am about to have been reading CFX help

"For a flow containing a continuous phase and a dilute dispersed phase, you should set the buoyancy reference density to that of the continuous phase"

My understanding is that the reference density should be that of the water. Do you believe this is correct?

Regards,

Sam

Glenn Horrocks January 8, 2009 17:23

Re: ANSYS CFX Tutorial 7
 
Hi,

Yes, you are correct.

Glenn Horrocks

Peter January 15, 2009 08:10

Re: ANSYS CFX Tutorial 7
 
Did you select both "Air at 25C" and "Water" in the fluid list when defining the domain?

Leandro Resende January 24, 2009 20:48

Re: ANSYS CFX Tutorial 7
 
Hi Sam,

Besides what Peter said, you should also set density reference (under gravity force vectors) as the one of the lighter fluid.

In The density difference model only the heavier fluid suffers the gravity force.

See at Help how this model works.

hope was helpful


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