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-   -   Subtracting 2 volumes (http://www.cfd-online.com/Forums/fluent/38106-subtracting-2-volumes.html)

 Vidya Raja October 4, 2005 21:03

Subtracting 2 volumes

Hi, I have an imported geometry of a solid model from ProE and I'm trying to create a cylinder around it and then subtract the volume of the solid from that of the cylinder to get the flow domain within and around the solid. But when I tried to subtarct the two volumes, I get an error message which says " CAN'T OPERATE ON VOLUME 2 WITH ASSOCIATED NON- REAL GEOMETRY". What does this mean and is there a way to solve this problem?

Thanks, Vidya

 zxaar October 4, 2005 21:16

Re: Subtracting 2 volumes

it means the volume imported has some virtual elements, gambit will not allow you to substract virtual volume from real one and give you a real volume. it seems that when you import gambit creates this. try importing in another form, till you get completely real volume after import. Avoid virtual volumes as much as possible, since they restrict lot of operations. Use virtual volumes only in the end when you are sure that everything is fine and you just need to mesh. Virtual volumes are great help in meshing, but not good help in preparing geometry for meshing.

 Sachin October 5, 2005 02:34

Re: Subtracting 2 volumes

In case you are not be able to get the real volumes through pro-e, just import the major dimentions and by extruding it in gambit you can easily made the volume. OR delete the virtual volume keeping lower geometry alive. and produce the volume again this will solve youir problem.

 Vidya Raja October 5, 2005 15:25

Re: Subtracting 2 volumes

If I retain the LOWE GEOMETRY option, and delete the cylinder, how will I produce it again for meshing? How can I create the symmetry plane, split it and do all thos eoperations?

 zxaar October 5, 2005 17:47

Re: Subtracting 2 volumes

i think what he means is delte only the volume but not the surfaces and vertices. Then out of remaining things construct the volume again by stiching the faces. well you can do so, but main problem is if the surface is virtual, then you need to delete them too, and create them again from surrounding edges. finally when you have all real surfaces make the volume out of them. In theory its perfect plan but in practical i doubt, most probably gambit will stop at some operation.

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