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Subject: Explicit Volume Creation With Internal Cavity?
Author: John Crawford
Date: 1999-09-03 11:11:00

Does anyone know how to explicitly create a volume with an inner cavity?
There is an undocumented command for creating areas with holes in them
(ALLP), but I can't find a similar command for creating a volume. My
problem is that I have a cooled turbine blade that I brought from CATIA
through CADFIX and into ANSYS. It has an internally contained cavity along
with the usual zig-zag array of cooling passages. CADFIX was able to create
the correct "body" (CADFIXese for a volume) with the internal cavity without
any problems. The ANF file was successfully read into ANSYS, and a VLIS
command showed the inner and outer loops which describe the volume.
However, if I select the volume and it's associated areas, delete the
volume, and then try to create the volume again from the selected areas,
ANSYS responds with the following error message.

*** ERROR *** CP= 4549.570 TIME= 07:13:48
Area list could contain multiple volumes.
Make sure areas enclose only one volume.

Since an undocumented command exists for creating areas with holes, I have a
slender thread of hope that a similar command exists for creating volumes
with cavities. Okay, so I'm a hopeless optimist. But if such a command
does not exist, one should be created, and it should be able to handle large
numbers of areas. For example, my volume has 11 areas on the inner cavity,
and 464 areas on the outer cavity. Maybe the command could use loop picking
to allow easy picking of the inner cavities and outer surface.

Of course, in an ideal world I'd just make a volume from the areas which
describe the outer surface, another volume from the areas which describe the
inner cavity, and then subtract the cavity volume from the outer volume.
But, in the real world we have the XOX geometry engine to deal with. I
tried this path and was greeted with the usual "Change BTOL and try again"
message. You know how this story ends.....

So, if anyone is aware of an undocumented command for making volumes with
cavities, I'd sure like to hear about it. In the mean time I'll return to
CADFIX, fix the area that is a little too warped for ANSYS to mesh, and then
start the process all over again.

One positive comment I have is that CADFIX seems to do a good job of
repairing geometry once you figure out how to use it. The terminology is
weird (SWARF is on the menu, but not in any American English dictionary I've
ever seen) and the menus aren't all that self explanatory. But the stuff
underneath works great. I've put through some pretty complicated geometries
and always managed to get something workable out of CADFIX. Maybe the best
part of this process is that CADFIX writes an ANF (ANSYS Neutral File)
format file which is read into ANSYS in /AUX15. This means that we avoid
ANSYS' IGES translator entirely, which isn't a bad thing. I've had very
good luck using CADFIX, and I am still not completely familiar with it. I
think as I continue using it I'll be able to do more and more things with
it. I can see why ANSYS Inc. is working on implementing CADFIX as a
geometry import front end to ANSYS, or so a recent press release says.

John Crawford
AlliedSignal Engines
Phoenix, AZ
john.crawford@a...

P.S. By the way, I was able to successfully import the blade model after I
cut it into 4 pieces in CATIA. I fixed it in CADFIX, and then read it into
ANSYS. Meshing wasn't a big deal, and everything went well. I was testing
the one volume method to see what it would take to successfully read it into
ANSYS and mesh it in one fell swoop.

Posts possibly associated with message #4415AuthorDateScore
4415Explicit Volume Creation With Internal Cavity?John Crawford1999/09/03 
4418Re: Explicit Volume Creation With Internal Cavity?Michael Hiller1999/09/03 
4433Re:Explicit Volume Creation With Internal Cavity?Dan McKenney dan.mckenney@1999/09/04