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posted by Thomas Nilsson at Feb 2, 2009 2:21 PM
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Hello dear SPIS comminty,

I'm currently working on simulations of Langmuir probes and I noticed the files Langmuir5.geo & Langmuir6.geo which are included with the SPIS package. (...Spis3_7RCDataExamplesOfCAD as well as the old version ...Spis3_6DataExamplesOfCAD).

Both have been written by Julien Forest during his time at IRF-K. (The Swedish Institute of Space Physics in Kiruna) and both of them have some small errors.

First of all, both versions of Langmuir6.geo lacks one point (It should be Point(1)={2,0,0,0.3};).

Secondly both Langmuir5.geo and Langmuir6.geo have two identical surfaces, (Line Loop (1000046) = {48, -128, 46, -51}; Ruled Surface (46) = {1000046}; Line Loop (1000047) = {48, -128, 46, -51}; Ruled Surface (47) = {1000047};).

The last of them, Surface 47, can be removed without any problems. Be sure to also remove the number 47 from Physical Surface 8 as well, it could be exchanged for 46 if you then remove physical surface 17!

Once this is done, one can easily see that the volume defined is incorrect. It does not exclude the Langmuir probe and this is due to the fact that Mr. Forest missed the surface 46 or 47 when he was choosing surfaces to be excluded as a hole in the volume. This requires the volume to be re-done! Most easily this is done in Gmsh, but it could of course be done manually.

The correct volume to be used is the following: Surface Loop(1100000) = {157, 155, 151, 153, 159, 161}; Surface Loop(1100001) = {25, 28, 32, 33, 37, 36, 30, 29, 35, 34, 31, 26, 27, 38}; Surface Loop(1100002) = {21, 22, 20, 24, 23, 19}; Surface Loop(1100003) = {53, 13, 65, 64, 8, 52, 51, 55, 67, 43, 45, 60, 10, 5, 3, 4, 2, 49, 40, 6, 7, 41, 14, 18, 16, 17, 15, 42, 44, 56, 57, 39, 58, 54, 9, 62, 59, 63, 46, 11, 61, 12, 48, 66, 50, 1}; Volume(165) = {1100000, 1100001, 1100002, 1100003};

And then it could be finished of with: Physical Volume(166) = {165};

The following is the OLD version which is to be replaced: Surface Loop (1000165) = {151, 153, 155, 157, 161, 159, 23, 22, 21, 20, 24, 19, 25, 28, 32, 33, 37, 36, 30, 29, 35, 34, 31, 26, 27, 38}; Volume (165) = {1000165}; Surface Loop (1099999) = {19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 151, 153, 155, 157, 159, 161, 38};

(Please note; Surface Loop 1099999 was not used at all.)

You may want to update these files for future releases of the SPIS package.

Best regards,

Thomas Nilsson

thomas.nilsson@m-sys.se

("Master of Science in Engineering Physics"-student, currently doing my final project work at IRF-U, The Swedish Institute of Space Physics in Uppsala)