Large mesh expansion Faktor due to prism layer
 

Hello,
I'm trying to get a nice prism layer around the blade of a wind turbine using ICEM.

At first I only put prisms around the blade but that either resulted in a only one prism at the Trailing Edge with stair stepping or really ugly prism-elements at the TE without stairs.
So I build a plane in the back of the TE by copying the TE 1m to the back (1 m is to large I guess, 50cm wouldve been enough). I was going to do stair steps here as I read in a post, because then I get nice elements but the transition between the last stairstep, where the first Prism element (2mm) faces the first tet (10 cm) is really big, so I tried it again without stairstepping, which only gives me bad prism elements 1 m behind the wing which I guess is better.

But even though my last prism element is around 10 cm thick which also should be the size of the tets (it was the max size of surface elements) I still get huge mesh expansion factors (thousands of elements with Exp.Fact. larger than 1000 and a couple of Elements as high as a million. Without the prism layer the biggest Exp.fact. was 28.

Is it normal that prismlayers produce larger Exp.Factors? Is there a better way of meshing the Prisms? Thanks a lot!


Edit:
I created a surface-Tri-mesh, smoothed it, created an volume-Delauney-mesh, smoothed it (quality >0.35) and did then 12 layers of prism with ratios between 1.25 and 1.5
as part of looking for a solution I also tried creating first the prismlayer and then the volumemesh, but that never worked. Does this way have different requirements on surface mesh or geometry than the other?

Is there no way how to control or fix the mesh expansion factor? I've been searching on the internet for hours and days and tried a lot, but without success...