How can I control the rate of mesh size away from the surface in ICEm CFD Tetra 10.0?
I have a surface with mesh size 2 and a volume mesh size of 16 say. Is there any way of controlling the rate that the tetra size increases from 2 through to 16 away from the surface? I know I could use density boxes with sizes 2, 4 & 8 but with a complex surface shape its not really an ideal option.
There is no direct way to get a nice smooth transition from your small cells to the larger background one. However, there are parameters which are available:
1) On the surface mesh control form is a value for Tetra size ratio ` this should control the rate of growth. It acts like a radius of influence as it extends the mesh control further into the domain, but still leaves the abrupt change in cell size.
2) On the tetra meshing form is a smooth transition whereby you should be able to set a value for the expansion. This switches the mesh technique from an Octree meshing approach to a Delauney. Once again the effect of doing this is still not very satisfactory.
Another two approaches, one which is as you suggested, is to use a density box, the other is to put an offset surface from the one with the mesh control and put a reduced mesh control on this surface.
In ICEM CFD 11.0 there will be the option to use the Advancing Front volume mesh algorithm which provides a much improved migration from small element sizes to the larger background size.