Element dimensions

JavyGlez · July 22, 2016, 13:54

Hi everybody:
I want to know the width, length and height of an specific element in an hexahedral mesh. Somebody can tell me how to obtain that information?
Thanks in advance!

mprinkey · July 22, 2016, 15:01

Unstructured meshes are built up from vertices -> edges -> faces -> cells. So, the dimensions that you are looking for are determined by the vertex locations. You will need to find the list of eight vertex location vectors and deduce the relevant length scales by considering the different edge lengths on the side.

You should also realize that there is not a single length, width, and height associated with general hexahedra. There can be no axis alignment assumed, opposite edges of a given face will not have the same length, etc.

JavyGlez · July 25, 2016, 09:48

Quote:

Originally Posted by mprinkey

Unstructured meshes are built up from vertices -> edges -> faces -> cells. So, the dimensions that you are looking for are determined by the vertex locations. You will need to find the list of eight vertex location vectors and deduce the relevant length scales by considering the different edge lengths on the side.

You should also realize that there is not a single length, width, and height associated with general hexahedra. There can be no axis alignment assumed, opposite edges of a given face will not have the same length, etc.

Hi Michael, thanks for your reply. In fact, that is my query, how to obtain that list of vertex location? Is there any kind of output file with this information?

mprinkey · July 25, 2016, 10:07

There is, but it is going to be different for each CFD code or mesh file. FLUENT has macros that allow you to loop over all of the vertices (nodes) on a face or cell:

Code:

c_node_loop(c,t,n)
 {   .   .  
  node = C_NODE(c,t,n); 
  .   . 
  }

Similar constructs likely exist for Star CCM+ and OpenFOAM.

JavyGlez · July 25, 2016, 10:11

I am using CFX, is the same as FLUENT?

mprinkey · July 25, 2016, 12:47

I have never coded for CFX, so I don't know those details. But the solver likely has access mechanisms similar to FLUENT and OpenFOAM. It is just a matter of reviewing the documentation.

JavyGlez · July 25, 2016, 13:20

Ok Michael, thank you very much for your information!

July 22, 2016, 13:54	Element dimensions	#1
JavyGlez New Member Javier Join Date: Jul 2016 Posts: 6 Rep Power: 9	Hi everybody: I want to know the width, length and height of an specific element in an hexahedral mesh. Somebody can tell me how to obtain that information? Thanks in advance!

July 25, 2016, 10:07		#4
mprinkey Senior Member Michael Prinkey Join Date: Mar 2009 Location: Pittsburgh PA Posts: 363 Rep Power: 25	There is, but it is going to be different for each CFD code or mesh file. FLUENT has macros that allow you to loop over all of the vertices (nodes) on a face or cell: Code: c_node_loop(c,t,n) { . . node = C_NODE(c,t,n); . . } Similar constructs likely exist for Star CCM+ and OpenFOAM.

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July 22, 2016, 15:01		#2
mprinkey Senior Member Michael Prinkey Join Date: Mar 2009 Location: Pittsburgh PA Posts: 363 Rep Power: 25	Unstructured meshes are built up from vertices -> edges -> faces -> cells. So, the dimensions that you are looking for are determined by the vertex locations. You will need to find the list of eight vertex location vectors and deduce the relevant length scales by considering the different edge lengths on the side. You should also realize that there is not a single length, width, and height associated with general hexahedra. There can be no axis alignment assumed, opposite edges of a given face will not have the same length, etc.

July 25, 2016, 10:11		#5
JavyGlez New Member Javier Join Date: Jul 2016 Posts: 6 Rep Power: 9	I am using CFX, is the same as FLUENT?

July 25, 2016, 12:47		#6
mprinkey Senior Member Michael Prinkey Join Date: Mar 2009 Location: Pittsburgh PA Posts: 363 Rep Power: 25	I have never coded for CFX, so I don't know those details. But the solver likely has access mechanisms similar to FLUENT and OpenFOAM. It is just a matter of reviewing the documentation.

July 25, 2016, 13:20		#7
JavyGlez New Member Javier Join Date: Jul 2016 Posts: 6 Rep Power: 9	Ok Michael, thank you very much for your information!