Slicing a Solid with a Contoured Surface
Slicing a Solid with a Contoured Surface
(OP)
I am attempting to run a CFD analysis on a car. I have been able to convert the 3ds Max file into a *.dxf, which imports to NX3 as a faceted body. I then "sewed" the multiple faces together, extracted geometry, and got a surface/sheet, which imports to Fluent.
The car's body is essentially one sheet, but it is approximated by flat surfaces instead of smooth curves, as it was built with polygons.
What I am trying to do is build a very large block of air (10x the characteristic length of the vehicle) around the vehicle, and have the sheet that represents the car's body slice the block of air, so a mesh and boundary conditions can be applied to it.
I can not split the block of air, it gives me the error "non manifold solid." I can not trim the block of air. I can not thicken the sheet, it tells me to lower the thickness. I can not use the sheet to solid assistant, as it tells me to use a smaller tolerance in relation to the thickness, but i went down several orders and this didn't do anything.
A picture can be uploaded later.
The car's body is essentially one sheet, but it is approximated by flat surfaces instead of smooth curves, as it was built with polygons.
What I am trying to do is build a very large block of air (10x the characteristic length of the vehicle) around the vehicle, and have the sheet that represents the car's body slice the block of air, so a mesh and boundary conditions can be applied to it.
I can not split the block of air, it gives me the error "non manifold solid." I can not trim the block of air. I can not thicken the sheet, it tells me to lower the thickness. I can not use the sheet to solid assistant, as it tells me to use a smaller tolerance in relation to the thickness, but i went down several orders and this didn't do anything.
A picture can be uploaded later.





RE: Slicing a Solid with a Contoured Surface
"Good to know you got shoes to wear when you find the floor." - Robert Hunter
RE: Slicing a Solid with a Contoured Surface
How am I supposed to find it with 16000 faces in the body???
RE: Slicing a Solid with a Contoured Surface
Best Regards
Hudson
www.jamb.com.au
Nil Desperandum illegitimi non carborundum
RE: Slicing a Solid with a Contoured Surface
RE: Slicing a Solid with a Contoured Surface
Best Regards
Hudson
www.jamb.com.au
Nil Desperandum illegitimi non carborundum
RE: Slicing a Solid with a Contoured Surface
I did a test case, one with a sinusoidal sweep that resulted in a 3-dimensional curve, and the other with a bunch of triangles (much like my geometry of the car) that were turned into sheets, sewed, and then attempted to thicken. The one like my car i'm trying to model, with all the triangles, will NOT thicken, and the complex 3-D curve will.
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RE: Slicing a Solid with a Contoured Surface
RE: Slicing a Solid with a Contoured Surface
Now as I said if you can find the area/s that cause problems sometimes it may be as simple and effective as removing an offending sheet from the sew in order to get the thicken to work. Depending on your specific needs you may be happy enough with that or easily able to fix the problem.
In examine geometry analysis alone is not sufficient to meet your needs then by all means trimming the body with planes in half and half again until you have isolated the offending area sometimes helps to focus in on small problems with large models.
Best Regards
Hudson
www.jamb.com.au
Nil Desperandum illegitimi non carborundum
RE: Slicing a Solid with a Contoured Surface
The thicken surface feature will work if i apply edge blends to each edge in the faceted body, creating a "smooth flow" from one face to the next.
I think what is happening is it attempts to thicken one face and it collides with the next face over, and creates discontinuities in the geometry. The edge blend worked for my test model, although I had to do most of the blending manually and separately. This will take a long time to do on a model that has 16,000 faces.
Once a solid is created, i can then subtract the geometry from the fluid block and apply my mesh!
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RE: Slicing a Solid with a Contoured Surface
I have tried to export a few parts out of NX with the .dxf option, but the result was unusable. If the surface was modeled with smooth curves, perhaps a different export option would take care of the problem. The first choice would be parasolid (.x_t) if it is available, otherwise STEP (.stp or .step) or IGES (.igs or .iges).
RE: Slicing a Solid with a Contoured Surface
Conversely in the same vein I have seen surfaces from other systems come in to NX in such a fashion though I have never seen NX create such a thing because of a translation. The only cases where I found NX making the equivalent of faceted surfaces was a degree 1 cloud of points surface with multiple patches.
Best Regards
Hudson
www.jamb.com.au
Nil Desperandum illegitimi non carborundum
RE: Slicing a Solid with a Contoured Surface
RE: Slicing a Solid with a Contoured Surface
Best Regards
Hudson
www.jamb.com.au
Nil Desperandum illegitimi non carborundum