# Thin Layer Modelling

Hi ,

I have recently started using FreeFEM for my PhD studying, but I have encountered a problem when I am trying to model very thin domains in 2D.

I am trying to define a really thin rectangular shape (length 0.2 mm and width 20 micrometer), but I constantly get the following error:

Exec error : Error points border points to close < diameter*1e-7

I am using the following code:

include “ffmatlib.idp”
int C1=1;
int C2=2;
real tapeWidth=0.012;
real thicknessAgEpoxy=2010^-6;
border C11(t=0., 1.){x=tapeWidth
t; y=0;label=C2;}
border C12(t=0., 1.){x=tapeWidth; y=thicknessAgEpoxyt;label=C2;}
border C13(t=1., 0.){x=tapeWidth
t; y=thicknessAgEpoxy;label=C2;}
border C14(t=1., 0.){x=0; y=thicknessAgEpoxyt;label=C2;}
int n=10;
mesh Th=buildmesh(C11(15
n)+C12(1)+C13(5*n)+C14(1));
plot(Th);

Am I missing some definition? The algorithm works when I define higher width values, so I assume there must be a definition of the minimum clearance that I have to do, but I couldn’t find something in the documentation/forum.

Thank you!

Regards,
Alex

I don’t know what you are doing but I think there is a typo,
After fixing the copied text and making this change it creates a coarse
mesh at both ends tapered towards the top.

``````    4 : real tapeWidth=0.012;
5 : //real thicknessAgEpoxy=2010^-6;
6 : real thicknessAgEpoxy=2010e-6;

``````
1 Like

Hi,

Thank you! That line should have been:
real thicknessAgEpoxy=20*10^-6;

I do not know why the multiplication sign between 20 and 10 did not show up. Yes it look like if I change to 20e-6 it does converge, but it is wired why when multiplying by 10^-6 would give an error.