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-   -   [DesignModeler] 3d irregular volume from XYZ coordinates? (http://www.cfd-online.com/Forums/ansys-meshing/101640-3d-irregular-volume-xyz-coordinates.html)

Bennp2000 May 9, 2012 14:05

3d irregular volume from XYZ coordinates?
 
1 Attachment(s)
Hi
I'm trying to firstly create a geometry that represents a natural channel (pond) that we have survery data for.

I have X Y Z coordinates in a txt file which I can import via Create, point etc. but from then on I'm not sure how to make that into a surface and then a volume (as I would have in Gambit?).

I basically need to level off the data to create a closed volume, the bottom of which is the shape of the natural channel, then specify an inlet and outlet and a few different fluid zones so I can control the permeability independantly.


The survey data is on a regularly spaced grid as shown in the attached image. Any help (or pointing me at videos etc.) is greatly appreciated.

Paul

Bennp2000 June 1, 2012 07:15

1 Attachment(s)
Right, I got a little bit further but once again I'm having issues:

I took my XYZ data and manipulated it using Matlab to give me one file containing all of the points within which the fluid should flow. Each contour of a given X was assigned a group.

This was read into DesignModeler as a 3D curve, leaving me with 50 or so curves. I joined the edges using "line from points", and then joined the high points on each section of constant x and then used each contour to create the bottom surface, and each line between the high points to create the top of the model.

This seems and looks fine, however, it won't mesh?
"The mesher did not generate any nodes"

In Gambit I would need to make a volume out of the faces (surfaces) I've created, have I missed a step?

Bennp2000 June 21, 2012 21:05

A last desperate bump? please? :confused:

jsm June 26, 2012 04:55

Hi Bennett,

It looks like you are creating surface from lot of points data and meshing this surface in ansys mesher.

From the image shown by you, I could not see any mistakes. Could you please check the model by edge connectivity. These small surfaces might not be connected with each other. Also could you tell me what kind of error you are getting when meshing?

For volume mesh generation, you need to have some closed surfaces. Otherwise it is not possible to create the volume mesh.

Bennp2000 June 26, 2012 05:56

Thanks for the reply.

I actually managed to generate a mesh in this last night, however I was missing a step:

Create points
Create edges from points
Create surfaces from edges
Body Operation -> Sew -> Create solid

Despite this I'm still having trouble sectioning off parts of the mesh to specify as seperate interior zones (so they can be made porous).

What I tried was generating a primitive (cube), and using a boolean operation to split the volume. This is then changed from solid to fluid on the LHS body menu.

This leaves me with two bodies but when I open it in fluent, the zone I'd like to be porous is surrounded by a wall. I've got one idea in mind to fix this (specifying a named selection as 'interior', but this didn't work due to overlapping selections) but do you have suggestions? (Thanks for taking the time to reply).

Paul

jsm June 26, 2012 07:53

Hi,

You are almost done. So you have two bodies separately right?
Just select both bodies in DM and right click and select "form new part" (I dont remember exact word). Then refresh the geometry in ansys mesher and check the geometry by connectivity. You should see single surface between two volumes.

Then mesh and export in to fluent. You can define that face as interior.

Bennp2000 June 26, 2012 08:16

Thanks for your help but unfortunately that doesn't appear to work (if i'm doing it correctly)?

I've produced the two bodies, then formed a part. However, when I open fluent there is still a wall boundary surrounding the porozous zone (i.e. a bondary/wall for each body that forms the part as well as an interior zone).

(I can post images if that would help?)

jsm June 26, 2012 08:31

Hi,

Did you checked this ? In Fluent boundary condition panel, for this particular surface, you can click the "Type" pop down menu and check there is interior option is available.

If not, then post geometry image in wireframe (with connectivity option) in ansys mesher.

PSYMN June 26, 2012 08:38

It looks to me like JSM had the right answer... Form a multibody part and then remesh... The new mesh will be conformal. I suppose you may also need to create Named selections for easy selection of the zones. Then when you get to Fluent, setup your internal walls, etc...

If you are still having troubles, we will need other details.

Bennp2000 June 26, 2012 08:48

3 Attachment(s)
Unfortunately I am; each section of the part still creates a wall boundary, there's no option for changing this to interior as suggested by JSM.


Quote:

If you are still having troubles, we will need other details.
No problem, I've attached a few screenshots to hopefully clarify a few things.

My named selections:
inlet - is one surface
outlet - another surface
freesurf - represents the free surface and is the top surface of both bodies in my part.

essentially I just need to remove the "nonvegetated wall" boundary.

I also tried using named selections for the fluid and porous zones as per 6:36 on this (your?) video: http://www.youtube.com/watch?v=-6Z2v8geroQ but again the wall appears around the 'porous' region.

Thanks for all the help so far btw, its very much appreciated.

jsm June 26, 2012 09:22

Hi,

You should have four named selections - inlet, outlet, outerwall and free surface (interior face - that you are telling between two bodies). But you have only three parts. It gives some confusion.

First you need to check named selection and then both bodies are connected well in DM.

Please check and if you could not find any things. then let me know.

If it is urgent, send the DM geometry file. I will look and come back to you.

Bennp2000 June 26, 2012 09:29

Quote:

Originally Posted by jsm (Post 368371)
Hi,

You should have four named selections - inlet, outlet, outerwall and free surface (interior face - that you are telling between two bodies). But you have only three parts. It gives some confusion.

First you need to check named selection and then both bodies are connected well in DM.

Please check and if you could not find any things. then let me know.

If it is urgent, send the DM geometry file. I will look and come back to you.

They are well connected. To generate the second body I subtracted a primitive from the main body (leaving a hole). I then built the second body from edges > surfaces > body operation, sew, create solid, to fill that hole. I need to be able to do this as in the future these shapes will be far more complex than primitives would allow.

I can email the geometry file (or upload it somewhere?) if people feel that'd be useful.


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