plot gradient of pde

Hi,

1) I solved the laplace equation and found the electric field using:

 u= assempde(b,p,e,t,c,a,f); %laplace equation on rectangle geometry
 [Ex,Ez] = pdegrad(p,t,-u); %find electric field
 ugrad = [Ex;Ez];

how to plot Ex and Ez as a function of (x,z) (seperatly, not as a quiver plot)?

• using tri2grid and plot it with "surf" is not an opption becouse the grid is very very large and it takes a lot of time to execute "tri2grid".

2) how can I find the values of Ex,Ez,U at the boundaries without using "tri2grid"?

• eventualy I need just the solution of U,Ex,Ez at the bounderies

Answer 1

[Alan Weiss]

Use pdeplot with the xydata name-value pair set to Ex or Ez. You could even set xydata to Ex and zdata to Ez.

Alan Weiss

MATLAB mathematical toolbox documentation

[d]

But as I understood, Ez is evaluated at the center of each triangle t.

when I'm Using

 pdeplot(p,e,t,'xydata',Ex);

doesn't it supposed to plot the values at the POINTS p?

[Alan Weiss]

Did you try my suggestion? It works for me:

[p,e,t] = initmesh(@lshapeg);
u = assempde(@lshapeb,p,e,t,1,0,1);
[ux,uy] = pdegrad(p,t,u);
pdeplot(p,e,t,'xydata',ux,'zdata',uy)

Look in the documentation, you see that you can give point OR triangle data to pdeplot.

Alan Weiss

MATLAB mathematical toolbox documentation