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Peter Devitt (peter_d)
New member
Username: peter_d

Post Number: 1
Registered: 07-2008
Posted on Tuesday, July 22, 2008 - 04:31 pm:   

I'm trying to model heat flow through a layered object but when I try to run the script I get the following error message: Cell 303 Nabor 427 Nonreceiprocal! Mesh is tangled near (0.220833,0.0295667)

Why is it doing this?

text/plainHeat Flow Model
Heat Flow.pde (4.3 k)
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Marek Nelson (mgnelson)
Moderator
Username: mgnelson

Post Number: 53
Registered: 07-2007
Posted on Tuesday, July 22, 2008 - 11:11 pm:   

The core of the problem is the way you have overlaped limited regions. A limited region in a layer cannot be cut by a region boundary in an adjacent layer. (The projections of the regions can share edges but cannot intersect.)

If you run your script with the "domain review", stop at "Layer 'inconel' Region1 'slabs' boundary shell" and rotate the grid, you can see how this error manifests itself. The grid seen from the top is not the same as the grid seen from the bottom. This causes the gridder to report a 'tangled mesh' error.

The attached simplified scripts 'bad_corner' and 'fixed_corner' show this in one of your checkerboard boxes. If you run the domain review as before, you can see that the error has been fixed in the second script. Unfortunately this means rewriting your definitions of the 'checkerboard' region.

------------------------

While looking at your script I noticed a few other unrelated things:
1)
You have declared two regions that have the same projection in the xy plane. In this case the first declaration is ignored. You should combine the two declarations. If you want different parameter properties and/or BCs you can prefix them with a layer qualifier.
2)
You have restated identical BCs on consecutive boundary path segments. This is not necessary. A stated BC applies to all following segments until explicitly changed.
3)
Similarly, if you have several regional parameter definitions in the same layer, you do not need to restate the layer qualifier.

In the attached script 'Heat_Flow2' I have changed these so you can take a look (though it still has the original error that needs to be fixed.)

application/octet-stream
bad_corner.pde (0.7 k)
application/octet-stream
fixed_corner.pde (0.9 k)
application/octet-stream
Heat_Flow2.pde (4.1 k)

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Peter Devitt (peter_d)
New member
Username: peter_d

Post Number: 2
Registered: 07-2008
Posted on Wednesday, July 23, 2008 - 11:30 am:   

Thanks for the help

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