[kordou]

Hi!

I am trying to model a windtunnel experiment and i have to apply a wall roughness on the ground equal to 1.53m.

In cfx for rough wall you need to specify the equivalent sand grain rougthness which is about 30*1.53. (according to this http://www.mi.uni-hamburg.de/fileadm...5-2007-www.pdf).

In the cfx manual there is the a notation about the cell size of the first cell. it says that the center of the first cell must not be smaller than the sand grain roughness. So for a wind tunnel of hight 200m (full scale) i have to have a fisrst cell with size 22.95m which is extremely hight.

any recomentation about how create this mesh?

P.S. the geometry is an empty simple rectangular box
P.S2. the ground material on the wind tunnel have roughness 0.0045m (full scale) of 0.0002 m (wind tunnel scale)

Thank you in advanced