Hi Olivier,
the TUBE you contructed describe no closed volume:
TUBE 4 , 4 , 16 + 32 ,
0 , 0 , 0 ,
0 , 0.015 , 0 ,
0.005 , 0.015 , 0 ,
0.005 , 0 , 0 ,
0 , 0 , 0 , 0 ,
0 , 0 , 0 , 0 ,
0 , 0 , REF_X , 0 ,
0 , 0 , 1 , 0
What you think does "16+32" mean? I dont'nt know!
Try this:
TUBE 4 , 4 , 1+ 2
0 , 0 , 0 ,
0 , 0.015 , 0 ,
0.005 , 0.015 , 0 ,
0.005 , 0 , 0 ,
0 , 0 , 0 , 0 ,
0 , 0 , 0 , 0 ,
0 , 0 , REF_X , 0 ,
0 , 0 , 1 , 0
1 + 2 ... means:
Masking
mask = j1 + 2*j2
with j1, j2 may be 0 or 1
j1 (1): surface at the beginning of the tube is present
j2 (2): surface at the end of the tube is present
Look at the "Output and Messages"-Control in Editor!
You get a good help there, if you klick the TUBE-command in the script.
With this usage of TUBE the GROUP_DIFF works fine (see enclosed test_group_tube1.smt)
Regards Jörg