[Gmsh] Boundary layers on a box

[Aditya Kommajosula]

Hello,

I am trying to create boundary layers on a 3D object - a box - and I was
having trouble creating it on select faces.

To be more specific, I am running Gmsh 3.0.2, and I have a box, 4 of whose
6 faces I would like to have boundary layers on. This is to capture
near-wall gradients as I'm trying to simulate fluid flow through a square
channel (the 4 faces being the channel walls). The code that I have for
creating boundary layers on a single face works and is as follows (a
template):

*Field[1] = BoundaryLayer;*
*Field[1].EdgesList = {1,2,3,4};*
*Field[1].NodesList = {1,2,3,4};*
*Field[1].hfar = 10;*
*Field[1].hwall_n = 2;*
*Field[1].ratio = 1.1; // default*
*Field[1].thickness = 1;*

I can do this for the 4 faces separately, but I do not know how to impose
all the fields at once on the meshing, since the 'Background Field' option
takes only one argument. I've also tried collapsing all fields into a
single field using 'Restrict', or 'Min', and then using this field as the
'Background Field', but this does not give me what I want. Finally, I've
also just tried specifying all the nodes and edges involved with the
'BoundaryLayer' field, but the mesh turns out to be uniformly refined all
over.

I'm out of ideas currently and I'd be grateful if you could help me with
this.

Thank you!

Regards
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