Can I assign values at nodal points for boundary condition?

Hi, I am working on a 2-D thermal modeling problem for a rectangular region. It is a simple conduction heat equation(elliptic) and I am solving using the pdetool. Except for the top surface other 3 boundaries follow neumann boundary conditions. For the top surface the values are constant , non zero and vary with every point. But the values don't follow any curve either, they are random values. When I initialize mesh, it assigns some nodal points on the top surface and I wish to assign numerical values to these nodal points. Can anyone please tell me how do I do that?

Answer 1

[Bill Greene]

This is not a standard function in PDE Toolbox but it can be done if you’re willing to do some programming.

One way to do this is by performing at least the solution phase in a MATLAB script rather than in pdetool. You can define your geometry, mesh, BCs (for now with a zero Neumann at the top), and PDE coefficients in pdetool and then export these to MATLAB. Or you could define the entire model in the script.

In the script, you first make a call to assempde with this form: [K,M,F,Q,G,H,R]=assempde(b,p,e,t,c,a,f); Then add an entry to the H and R matrices for each node on the top edge(I’ll assume you know how to identify the top-edge nodes where you want to prescribe values). Then call this form of assempde: u=assempde(K,M,F,Q,G,H,R);

Bill