non orthogonality of mesh due to curvature of nsurfaceLayer in snappyHexMesh
 

hello to everybody
In snappyHexMesh i need to generate 5 layers of 4 mm thickness around a halved cyrcle (as shown in attachemet). but by increasing thickness (even for one layer), the whole mesh becomes like curvature because it wants to take the shape of the halved cyrcle. this curving (non orthogonality of the mesh) makes the field of velocity and ... to changed and even to divergence.
finally in "addLayersControl" i found that "featureAngle" effect on orthogonality. but by reducing the angle to 5 degree, the whole layers will be losen.
does any one have any suggestion how i can have forexample 5 layers paralel to the radius of my cyrcle while keeping the rest of mesh ortho?
thanx a lot