[Gmsh] transfinite surfaces

[Dr Colin J. Cotter]

Dear Gmsh,
	I'm trying to make a structured mesh that has fine vertical resolution
in a middle layer, and then gradually increasing resolution at the top
and the bottom. I thought I might be able to do this using the
transfinite surface algorithm, but what I got was that the mesh graded
the resolution at the sides, but adjusted to equispaced resolution in
the middle. What did I do wrong?

I have included the .geo file at the bottom of this email.

all the best
--Colin


lc = 0.05;
H = 1.0;
L = 10.0;
LayerH = 0.1;
BottomLeft = newp; Point(BottomLeft) = {0.0, -H, 0, lc};
BottomRight = newp; Point(BottomRight) = {L, -H, 0, lc};
TopRight = newp; Point(TopRight) = {L, H, 0, lc};
TopLeft = newp; Point(TopLeft) = {0.0,H,0,lc};
LayerBottomLeft = newp; Point(LayerBottomLeft) = {0.0, -LayerH, 0, lc};
LayerBottomRight = newp; Point(LayerBottomRight) = {L, -LayerH, 0, lc};
LayerTopRight = newp; Point(LayerTopRight) = {L, LayerH, 0, lc};
LayerTopLeft = newp; Point(LayerTopLeft) = {0.0,LayerH,0,lc};

Bottom = newl; Line(Bottom) = {BottomLeft, BottomRight};
BelowRightL = newl; Line(BelowRightL) = {BottomRight,LayerBottomRight};
LayerRightL = newl; Line(LayerRightL) = {LayerBottomRight,LayerTopRight};
TopRightL = newl; Line(TopRightL) = {LayerTopRight,TopRight};
Top = newl; Line(Top) = {TopRight,TopLeft};
TopLeftL = newl; Line(TopLeftL) = {TopLeft,LayerTopLeft};
LayerLeftL = newl; Line(LayerLeftL) = {LayerTopLeft,LayerBottomLeft};
BelowLeftL = newl; Line(BelowLeftL) = {LayerBottomLeft,BottomLeft};

AboveLayer = newl; Line(AboveLayer) = {LayerTopLeft, LayerTopRight};
BelowLayer = newl; Line(BelowLayer) = {LayerBottomLeft, LayerBottomRight};

Line Loop(1) = {Bottom,BelowRightL,-BelowLayer,BelowLeftL};
Plane Surface(1) = {1};
Line Loop(2) = {BelowLayer,LayerRightL,-AboveLayer,LayerLeftL};
Plane Surface(2) = {2};
Line Loop(3) = {AboveLayer, TopRightL, Top, TopLeftL};
Plane Surface(3) = {3};

layerwidth = 20;
outsidelayerwidth = 20;
domainwidth = 20;
outsideprogression = 1.1;

Transfinite Line{Bottom} = domainwidth+1;
Transfinite Line{Top} = domainwidth+1;
Transfinite Line{AboveLayer} = domainwidth+1;
Transfinite Line{BelowLayer} = domainwidth+1;
Transfinite Line{BelowRightL} = outsidelayerwidth+1 Using Progression
1.0/outsideprogression;
Transfinite Line{TopRightL} = outsidelayerwidth+1 Using Progression
outsideprogression;
Transfinite Line{BelowLeftL} = outsidelayerwidth+1  Using Progression
outsideprogression;
Transfinite Line{TopLeftL} = outsidelayerwidth+1  Using Progression
1.0/outsideprogression;
Transfinite Line{LayerLeftL} = layerwidth+1;
Transfinite Line{LayerRightL} = layerwidth+1;