Error in the formula for internal extrusion

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Error in the formula for internal extrusion

Postby gagliar » 10 Feb 2017, 16:25


I think there is a small error in the formula to compute the space between nodes when using the internal extrusion with the keyword "Extruded Mesh Ratio".

By definition in the documentation, Extruded Mesh Ratio is the ratio between the first and the last element and the element size is assumed to follow a geometric progression.

I made a test with
Extruded Mesh Levels = Integer 11
Extruded Mesh Ratio = Real 4.0
which do correspond to 10 layers and I expect that h_1 / h_10 = 4

The different h_i are
h_1 0.172599
h_2 0.150257
h_3 0.130805
h_4 0.113873
h_5 0.099133
h_6 0.086299
h_7 0.075128
h_8 0.065403
h_9 0.0569369
h_10 0.0495661
which is a geometric progression of common ration r = 1.1487

The ratio h_10/h_1 is 3.48 (which is r^(n-1)) where I would expect it to be 4 (and 4 = r^n)

Solution is in MeshUtils.F90 at lines 9816 and 9820 where 1.0_dp/n should be modified by 1.0_dp/(n-1)

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Re: Error in the formula for internal extrusion

Postby raback » 14 Feb 2017, 01:30

Hi Olivier

Ok. This is now fixed.

The "Extruded Mesh Levels" has been somewhat difficult keyword as it refers to node levels rather than elements levels. So I added also the keyword "Extruded Mesh Layers" that is one smaller i.e. it reflects always the number element layers.

Thanx for reporting!

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