[ICEM] Meshing Size Problem

eRzBeNgEl · April 14, 2011, 08:48

HI Guys

I am using Icem CFD 12.1 and I need help with following problem.

My standard Model consists of 500.000 Elements.
My Global Size Setup is:
Skale Factor: 1
Global Mesh Size: 32
Proximity Based Refinement - Activated : Min Size Limit 1

For getting a higher mesh resolution I created a Density and set the Size to 16! Now i got a Mesh of 750000 elements.

Well the next step is to increase the mesh size to 1.000.000 elements. When I enter now in the Density Mesh size 15. the total number of elements increases to 22.000.000! I don't get it? What I am doing wrong?

Thanks for help

PSYMN · April 16, 2011, 11:56

Octree refinement works in Powers of 2... Actually powers of 2 based on your minimum size, and then multiplied by your scale factor...

If you change the max size in your density from 16 down to 15, it drops to the next power of 2, which is 8. In 3D space, and worse with tetras in clumps of 12, that very quickly increases your number of elements.

If you just want to tweak your mesh size a little, use the scale factor. Change it from 1.0 down to 0.9 and see how it goes...

This would mean that your size 16 would become 16*0.9 = 14.4...

You can read more about Octree powers of two in the help or on many other cfd-online postings.

eRzBeNgEl · April 17, 2011, 15:53

Thanks a lot! I got it now :-)

April 14, 2011, 08:48	Meshing Size Problem	#1
eRzBeNgEl Senior Member Join Date: Dec 2010 Posts: 135 Rep Power: 15	HI Guys I am using Icem CFD 12.1 and I need help with following problem. My standard Model consists of 500.000 Elements. My Global Size Setup is: Skale Factor: 1 Global Mesh Size: 32 Proximity Based Refinement - Activated : Min Size Limit 1 For getting a higher mesh resolution I created a Density and set the Size to 16! Now i got a Mesh of 750000 elements. Well the next step is to increase the mesh size to 1.000.000 elements. When I enter now in the Density Mesh size 15. the total number of elements increases to 22.000.000! I don't get it? What I am doing wrong? Thanks for help

April 16, 2011, 11:56	Octree Powers of 2	#2
PSYMN Senior Member Simon Pereira Join Date: Mar 2009 Location: Ann Arbor, MI Posts: 2,663 Blog Entries: 1 Rep Power: 47	Octree refinement works in Powers of 2... Actually powers of 2 based on your minimum size, and then multiplied by your scale factor... If you change the max size in your density from 16 down to 15, it drops to the next power of 2, which is 8. In 3D space, and worse with tetras in clumps of 12, that very quickly increases your number of elements. If you just want to tweak your mesh size a little, use the scale factor. Change it from 1.0 down to 0.9 and see how it goes... This would mean that your size 16 would become 16*0.9 = 14.4... You can read more about Octree powers of two in the help or on many other cfd-online postings. __________________ ----------------------------------------- Please help guide development at ANSYS by filling in these surveys Public ANSYS ICEM CFD Users Survey This second one is more general (Gambit, TGrid and ANSYS Meshing users welcome)... CFD Online Users Survey

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April 17, 2011, 15:53		#3
eRzBeNgEl Senior Member Join Date: Dec 2010 Posts: 135 Rep Power: 15	Thanks a lot! I got it now :-)