Hello,

I have a question about the implementation of stress free BC, actually i have a system of equations with 6 unknown (u1,u2…u6), i want to impose this BC on the u2 and u4.

dn(u1)=-u2/(4*r0) with dn the normal derivative of u1

and dn(u4)=2(r-r0)*u4/(r *r0)

Is it possible to implement this two conditions at the same time with FreeFem++ ?

Any help,

Thank you,