Search All of the Math Forum:

Views expressed in these public forums are not endorsed by NCTM or The Math Forum.

Topic: Boundary conditions in PDE solver ?
Replies: 1   Last Post: Mar 15, 2013 3:55 AM

 Messages: [ Previous | Next ]
 Torsten Posts: 1,684 Registered: 11/8/10
Re: Boundary conditions in PDE solver ?
Posted: Mar 15, 2013 3:55 AM

> 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.

Date Subject Author
3/14/13 DRG
3/15/13 Torsten