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3D meshing in Ga,bit

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Old   August 16, 2005, 15:09
Default 3D meshing in Ga,bit
  #1
Aly
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My question is related to meshing in GAMBIT. It is a 3d geometry circular pipe geometry with 2 inlets one at the bottom (water) and other at 1m from base (for air). Geometry is made from Pipe-pipe intersection by thin rectangular brick.

outlet

| |

| |

| |

| |

| airinlet (90 degree inlet)

| |

| |

waterinlet

when i try to edge mesh (inlet circular domain) before putting boundary layer .............the inlet surface (consisting of 5 segments) meshes in nonuniform manner i.e. each segment makes different nodes.

Is there any option or procedure in gambit through which i can uniformly distribute nodes over entire inlet circular surface (let say 60 nodes over all circular domain)i.e. while circular domain consists of 5 segemnts.

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Old   August 16, 2005, 15:42
Default Re: 3D meshing in Ga,bit
  #2
Jason
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You can specify how many nodes you want on any edge. There's a drop down box next to where you put the interval size and you can change that to interval count. You can select all the edges you want to have the same number of nodes and mesh them all at the same time by specifying the interval count. Is that what you were looking for? Or is the node spacing non-uniform along the edge segment (i.e. the first node spacing on the edge is .1m, but the next node spacing is .2m or something like that)?

Good luck, Jason
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Old   August 16, 2005, 18:51
Default Re: 3D meshing in Ga,bit
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Aly
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thanks for the reply.

Yes i did the same way as u have said but it did not work due to geometry made of three volumes two pipes at 90dgree joined by thin rectangular brick.

This means if u look from top (or down)) one will see 3 segment on the circular surface(diameter of pipe). if i select interval count and select all the edges than the distribtuion of nodes are uniform for 2 opposite sides i.e. small edges gives same number of clustered nodes which large edges gives uniform.

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Old   August 17, 2005, 09:43
Default Re: 3D meshing in Ga,bit
  #4
Jason
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Oh, so the edges have different lengths?

Not sure if there's an automatic way to do this then. If you can merge the edges then it'll space them evenly. Otherwise, you can get the arc length of each line segment (using the Summarize command in the Geometry-Edge operations... it looks like an i). Then you can calculalate how many nodes should be on each segement to get approximately even increments.

Nodes on i = Length of i / (sum of all L) * Total Number of Nodes on Loop

You'll have to round the numbers to even integers, but this might help.

Hope this helps, and good luck, Jason
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Old   August 18, 2005, 15:55
Default Problem importing a .cas file from gridgen
  #5
derick
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I am working on an electrostatic precipitator and started of with a simple 2D mesh. I was trying to load this in Fluent and it gives me an error: "invalid section id". can someone please tell me what the problem is.

thanks in advance
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Old   August 18, 2005, 16:02
Default Re: Problem importing a .cas file from gridgen
  #6
Miqdad
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Derick,

Have you tried creating blocks for each domain? I know its a bit stupid the way Gridgen works but you can try that and let me know if it works.

Many thanks, Miqdad
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Old   August 19, 2005, 11:10
Default Re: Problem importing a .cas file from gridgen
  #7
derick
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hey Miqdad,

i got the thing rectified...well it was some problem with the way i was exporting the .cas file. thanks for the help. but surely more to come!! derick
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Old   August 19, 2005, 14:49
Default Re: Problem importing a .cas file from gridgen
  #8
Miqdad
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No problems at all,

Let me scare you a bit. After you read the mesh in Fluent, check your grid for negative volume to make sure its a proper grid. If you see any negative volume there then some thing is not right!

Thanks, I know there is more to come.

Good luck and keep posting.
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Old   August 19, 2005, 15:38
Default Re: Problem importing a .cas file from gridgen
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sam
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yeah negative volume means inverted volumes. and wat is inverted volume i dont know :S i think it is something to do with singularity . am i right ?
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