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Torsten
Posts:
1,626
Registered:
11/8/10


Re: Solving an unusual system of ODES
Posted:
Apr 10, 2013 2:44 AM


D R G <grimesd2@gmail.com> wrote in message <ea631802c9414e7898323561e21842bf@googlegroups.com>... > > On Tuesday, April 9, 2013 2:15:07 PM UTC+1, Torsten wrote: > > D R G <grimesd2@gmail.com> wrote in message <5c50216110e948639e7657617f33fb35@googlegroups.com>... > > > > > Yes, that is what I want to solve; however, the case you're referring to is I believe the trivial case; we have already solved for when k = 0, and got a nontrivial solution. As K is small, this will be close to it and there will be non zero solutions. > > > > > > > > > > Regards > > > > > > > > > > DRG > > > > > > > > > > > > > No, y=0 is the only solution that satisfies your differential equation together with the two boundary conditions  also for the case K and/or J not equal to 0. > > > > You will have to change the boundary conditions to get a solution different from y=0. > > > > > > > > Best wishes > > > > Torsten. > > Hmm.. that is quite unexpected! Alright, so can we extend this for the case > > C(RN) = 0 > dC/dr (RN) =! 0 ? > > Thanks in advance > > DRG
In the case dC/dr (RN) not equal to 0 you will get a nontrivial solution. When you use ODE45 to solve, just interpret the time variable as the space variable:
dX(1) = X(2) dX(2) = J*X(1)/(X(1) + K)  2/t*X(2)
Usually stationary secondorder ODEs are boundary value problems  i.e. one boundary condition is given at RN and the second at RO. Are you sure the physics of your problem leads to two boundary conditions at RN ?
Best wishes Torsten.



