# Math Help - robin boundary condition

1. ## robin boundary condition

I have the robin bc --- u(1,t) + 2u_x(1,t) = 0, t>0.

What is the physical meaning of the boundary condition?

2. Originally Posted by CarmineCortez
I have the robin bc --- u(1,t) + 2u_x(1,t) = 0, t>0.

What is the physical meaning of the boundary condition?
The flux (the flow of heat) is $k u_x$. No flux boundary conditions (i.e. $u_x = 0$) says there is no flow of heat - insulated. So saying

$u_x = c u$ is saying the flux is proportional to the heat - the larger the heat the larger the flow.

3. so if u(1,t) <0 then flux >0 which means heat is flowing into the rod?