meshing a pipe attached to a channel floor

Discussion about meshing issues.

meshing a pipe attached to a channel floor

Postby aelghany » Mon Apr 08, 2013 12:47 am

Hi
I am new to Cubit. I am designing a mesh for a 3D pipe with circular cross section that is attached to the bottom surface/floor of a 3D duct/channel with rectangular cross section. I can only uses hex/quad elements and structured mesh.
My problem is designing a transition region to transition from the pipe mesh to the channel mesh. My pipe mesh is generated by meshing one surface ( let say the pipe inlet outside the duct) using a circle scheme with nice control over the number of outer circles and the fraction of the interior mesh..etc) and it looks good and I then sweep it to the outlet of the pipe which lies on the channel floor.
reset
brick x 11 y 2 z {2.0*PI}
volume 1 move x 5.5
create cylinder height 1 radius 0.1
rotate volume 2 about x angle 90
move volume 2 location x 1 y -1.5 z 0

since my channel floor is hexes/quads, I realized there will be a transition region around the circular inlet. How can I make this transition? also it seems if I swept the channel floor mesh to its top surface then I will need to define a virtual circular surface on the top surface of the channel

- I will also have to locally refine the mesh around the circular inlet section over a volume extending into the channel may be up to the center of the channel or a bit higher or all the way to the top surface. The horizontal base of this volume will contain the circular part plus the transition region..etc. I might also refine through a volume/region inside that volume/region..etc


thanks a lot
aelghany
 
Posts: 5
Joined: Mon Apr 08, 2013 12:02 am

Re: meshing a pipe attached to a channel floor

Postby csimsoft Moderator » Tue Apr 09, 2013 9:44 am

If I understand correctly, this might help:

To control the transition you can add an additional piece of geometry and control the mesh in that location.

In this example, I created an additional cylindrical volume around the cylinder. I used a scheme hole on the surface bounding the cylinder (note that the -2 bias indicates that the small bias will be close to the center of the hole).

reset
brick x 11 y 2 z {2.0*PI}
volume 1 move x 5.5
create cylinder height 1 radius 0.1
rotate volume 2 about x angle 90
move volume 2 location x 1 y -1.5 z 0

webcut volume 1 with cylinder radius .5 axis y center 1 -2 0
imprint all
merge all

Curve 14 interval 16
surface 9 scheme circle fraction 0.5
Volume 2 size 0.1

surface 17 scheme hole rad_intervals 7 bias -2
vol all scheme auto
mesh vol all
csimsoft
csimsoft Moderator
 
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Joined: Tue Feb 14, 2012 5:59 pm
Location: American Fork, UT

Re: meshing a pipe attached to a channel floor

Postby aelghany » Tue Apr 09, 2013 1:51 pm

Thanks for getting back to me.
it seems for better control one should subdivide the channel into multiple blocks. The worst of which would be the one containing the circular piple. but if that block is symmetric it is possible to get a really smooth mesh. So by meshing the surfaces of those blocks and then sweeping them all the way to the top; that might potentially be a very good solution. For the bottom surface meshes of couple of those blocks have a look at this
reset
create surface rectangle width 3 zplane
create surface circle radius 1 zplane
subtract volume 2 from volume 1 keep
move surface 1 location X 3 nomerge
surface 1 interval size 0.075
surface 3 interval size 0.075
surface 1 scheme auto
surface 2 scheme circle
surface 3 scheme hole
imprint all
merge all
mesh surface 3
mesh surface 1
mesh surface 2
thanks
Ammar
aelghany
 
Posts: 5
Joined: Mon Apr 08, 2013 12:02 am


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