# How to divide the region for 3D geometry in ANSYS CFD Post

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November 26, 2014, 21:21
How to divide the region for 3D geometry in ANSYS CFD Post
#1
Member

Naimah
Join Date: Nov 2011
Posts: 58
Rep Power: 12
Hi,

I have a complex and irregular shape of the geometry (Please find the attached file)
May I know, how to divide the geometry into different region and calculate for the volume for each region.

Thank you

Naima
Attached Images
 CFD Post2.jpg (56.9 KB, 23 views)

 November 27, 2014, 09:22 #2 New Member   Koen Join Date: Jan 2014 Posts: 11 Rep Power: 10 Hi, Any chance you divided the domains before the simulation? In CFX Post you can put "=volume()@S1" in a table to calculate the volume of a domain, where 'S1' is your domain name. If it is just one domain, then I don't know how to do this in Post.. If you have the CAD-files where they are specified as different parts, you could specify them as different domains in CFX-pre and then run the simulation. Then you can gather information for a specific domain.

November 27, 2014, 23:23
#3
Member

Naimah
Join Date: Nov 2011
Posts: 58
Rep Power: 12
Thank you KWG for the useful information.

I have tried out the example of equation that you had given.
Let say I want to calculate the volume of velocity lambda-2 in a domain name as volume 2.

But the error message pop up (Please find the attached file).
May I know, how to solve for this.

Thank you again

Naimah
Attached Images
 image 1.jpg (42.5 KB, 15 views) image 2.jpg (51.2 KB, 11 views)

November 28, 2014, 03:45
#4
New Member

Koen
Join Date: Jan 2014
Posts: 11
Rep Power: 10
Hi,

Your second picture (which says syntax error) is because you shouldn't use the ''='' when you write an expression. Your first picture, from what I understand, is that CFX is expecting zero arguments in the formula for volume. You put "velocity lambda-2" in the expression, but you should just leave it blank.

You can either write the formula in a table (picture 1) or as an expression (picture 2) to calculate the volume of a domain. Note that in the expression you don't use the "=".

Let me know if this is exactly what you want and if this solves your problem.
Attached Images
 1.jpg (20.1 KB, 12 views) 2.png (9.3 KB, 13 views)

November 28, 2014, 04:24
#5
Member

Naimah
Join Date: Nov 2011
Posts: 58
Rep Power: 12
Hi KWG,

It is very helpful. Thank you so much.

I have 1 more question,let say I have region of interest (ROI)(as in the circle in the attached file).
I can calculate the volume of that region based on the method that you showed.
If I want to calculate the volume of variable eg velocity lambda-2 at certain threshold at that ROI, how i am going to do that? Is that Possible?

Thank you

Naima
Attached Images
 Image 3.jpg (35.3 KB, 8 views)

 November 28, 2014, 04:43 #6 New Member   Koen Join Date: Jan 2014 Posts: 11 Rep Power: 10 I don't think that is possible. From what I found in the CFX reference guide is that you cannot define any argument in the volume formula. I am also not familiar with this variable velocity lambda-2, what does it represent? From the CFX Reference Guide: 14.5.29. volume Calculates the volume of a 3D location. volume()@ where: • is any 3D region (such as a domain or subdomain). An error is raised if the location specified is not a 3D object. For details, see volume (p. 177).

 November 28, 2014, 04:54 #7 Member   Naimah Join Date: Nov 2011 Posts: 58 Rep Power: 12 Thank you KWG, As far that I understand lambda-2 is the indication which part is consider as a vortex. Actually my main interest is to know whether the volume of this lambda-2 at certain part can be calculated or not.