[ff3d-users] Robin boundary conditions

[Benoit_Desjardins]

Hello Stephane

thanks a lot for the vtk reader. It works perfectly !

I tried recently to use Robin type boundary conditions
for simple academic problems like:

vector n = (100,10,10);
vector a = (0,0,0);
vector b = (1,1,1);
mesh M = structured(n,a,b);
solve(u) in M
memory(matrix=none),
method(type=penalty)
{
pde(u)
-div(grad(u)) = 0;
dnu(u) + u = 2. on M xmax;
u=0. on M xmin;
};
save(vtk,"temperature",u,M);

it computes the right solution. But as soon
as I try to multiply "u" by something, I get
a syntax error.

dnu(u) + 3*u = 2. on M xmax;

maybe I missed something with the way the
boundary conditions have to be expressed ?

thanks for your advice

Best regards

Benoit

[Stephane Del Pino]

Hello Benoit.

Yes. There is a stupid bug in the parser that is not easy to fix about that.
You must declare a function alpha

function alpha = 2;

then write the robin condition this way

alpha*u + dnu(u) = 2. on M xmax;

Best regards,
Stéphane.