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[ICEM] Double Y grid and single Y grid

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Old   July 21, 2009, 04:42
Default Double Y grid and single Y grid
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Ben
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Hi,

I am currently trying to mesh the appendages for a submarine hull form using ICEM,

I have found that Y gridding is the most effective, however as the fwd edge of the appendages is quit round a single y grid results in an elements with large angles (180 degrees) leading into the farfield from the nose, I found that to decrease this angle, 2 y grids can be used and the mesh elemnts are a good shape,

When I try to do this though I get strange errors, I usually get extra randomly orientated edges forming inside the submarine, I have attached pictures so you can see what i am mean. I managed to get 1 appendage out (the sail), but folloing the same method I can not seem to get the aft appendages (fins) to work.

Any suggestions would be very helpful,

Also when I create the y grid I delete the block and then create a new block using the create y grid function, is this the best method to create a y grid?


Ben
Attached Images
File Type: jpg 1 y grdis fwd 1 aft blocks.jpg (62.3 KB, 122 views)
File Type: jpg 2 y grdis fwd 1 aft blocks.jpg (65.7 KB, 94 views)
File Type: jpg poor cell on fwd edge -1 y grid.jpg (84.9 KB, 95 views)
File Type: jpg good cell on fwd edge double y grid.jpg (84.7 KB, 82 views)
File Type: gif Double edges.gif (8.6 KB, 70 views)
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Old   July 21, 2009, 04:45
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here is another picture of some more errors,

Ben
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File Type: gif extra edges.gif (19.1 KB, 55 views)
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Old   July 22, 2009, 12:18
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Simon Pereira
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These sorts of topologies must propagate completely thru the model. It looks like this is not the case here.

One way to check would be to save a copy and extend all the splits...
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Old   July 27, 2009, 07:32
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Thanks for your help simon,

I can see how propogating all the way through the opology would work for a single appendage, however for four fins at 90 degrees intervals around the hull the topology inside the hull where they all cross becomes extremly complex, especiailly with the C gridding sorrounding the appendages.

I extend the topology all the way to the limits of the Farfield but i terminate the splits at inside the hull. could this be the source of my errors?
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Old   July 27, 2009, 08:27
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It is fine if they terminate inside the hull, but they must propagate thru the hull first and terminate in the dead region. one of your pics made it look like you pinched it out against the hull, but still outside.

You may recall I predicted these issues when this question was first asked on another thread. There, I suggested how I have done geometries like this previously. I am not saying you can't still sort this out by moving forward, but if you do start over, perhaps trying that method will work for you.
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Old   July 27, 2009, 09:24
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Thanks mate, I will try to have a look at that previuos thread,

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