Hello Hagar Bernad
                            
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                                                Posted:
                            
                                1 decade ago                            
                            
                                20 juil. 2014, 17:32 UTC−4                            
                        
                        
                                                    Hello, 
You might have figured this out already, but you can do a right mouse click on "Geometry" and select "cylinder." Once you model the first cylinder, you can then place a second cylinder of smaller diameter on the same cartesian axis coordinates as the first cylinder. 
If you make the outside cylinder shorter than the internal cylinder, you can probably design two cones, one for each end, that closes the gap between the two cylinders. 
With that said, I am not sure "why" you "might" want a cylinder within a cylinder to model flow. If you are trying to develop a "thickness," in order to model the muscle layers of an artery, you can probably adjust the thickness of the cylinder and then attempt to apply a specific material type with properties. I have not done this though so I cannot say it is possible.                                                 
                                                
                            Hello, 
You might have figured this out already, but you can do a right mouse click on "Geometry" and select "cylinder." Once you model the first cylinder, you can then place a second cylinder of smaller diameter on the same cartesian axis coordinates as the first cylinder. 
If you make the outside cylinder shorter than the internal cylinder, you can probably design two cones, one for each end, that closes the gap between the two cylinders. 
With that said, I am not sure "why" you "might" want a cylinder within a cylinder to model flow. If you are trying to develop a "thickness," in order to model the muscle layers of an artery, you can probably adjust the thickness of the cylinder and then attempt to apply a specific material type with properties. I have not done this though so I cannot say it is possible.