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Torsten
Posts:
1,674
Registered:
11/8/10


Re: Boundary conditions in PDE solver ?
Posted:
Mar 15, 2013 3:55 AM


D R G <grimesd2@gmail.com> wrote in message <5eb70b4f9f30460e87c0b12526e7ad47@googlegroups.com>... > I'm having some difficulty understanding the required input for matlab PDE boundary conditions. Essentially, I have a function U that has the following boundary conditions; > > U(r) = 0 > dU/dr(r) = 0 > > how can I code these up into the form > > pl = > ql = > pr = > qr = > > I understand they must be the the p(x,t...) + q(x,t...).. = 0 form, but I am not sure how to proceed..
Put your boundary conditions in the required form: u=0 can be written as u+0*f = 0, thus p=u and q=0 ; du/dr=0 can be written as 0+1*f=0, thus p=0 and q=1 (assuming that f=constant*du/dx for your system of pdes). Thus pl=0, ql=1, pr=ur, qr=0 (if u=0 is the boundary condition at the right end of your domain and du/dr=0 is the boundary condition at the left end of the domain).
Best wishes Torsten.



