[Date Index]
[Thread Index]
[Author Index]
Re: partial differential equation of diffusion
*To*: mathgroup at smc.vnet.net
*Subject*: [mg88377] Re: partial differential equation of diffusion
*From*: "Ali YILDIRIM" <ayildirim10 at hotmail.com>
*Date*: Sat, 3 May 2008 06:17:34 -0400 (EDT)
*References*: <BLU129-DS716E7490C4367AC35F1EEA8DB0@phx.gbl> <22d35c5a0805012309s10c21a53me6a645fcb0be5a64@mail.gmail.com>
Dear Jean Marc Gulliet,
>>When I put my equation as D[M[r, t], t] == a*(D[M[r, t], r, r] +
>>(2/r)*D[M[r, t], r]) - k*M[r, t] in to mathematica
>and initial and boundary condition as M[r, 0] == M0, D[M[0, t], t] == 0,
>M[R, t] == Ms
>It can not solve. The mathematica notebook is given in attachment.
>Best regards
> > dM/d t =a[d^2 M//dr^2 +(2/r) (dM/dr)]-kM
>> > The differentials are partial differentials.
>> > a and k are constants.
>>>
>>
> Do you mean that you do not know how to multiply expressions with
> Mathematica? If this is the case you should familiarize yourself with
> the basis of Mathematica syntax, this will really help you and be a
> time saver in the future.
>
> D[M[r, t], t] ==
> a*(D[M[r, t], r, r] + (2/r)*D[M[r, t], r]) - k*M[r, t]
>
>> >Best Regards..
>> >
>> >
>> Ã?Ä?r.GÃ¶r. Ali YILDIRIM
>> Gaziantep Ã?niversitesi
>> Nizip Meslek YÃ¼ksekokulu
>> GÄ±da Teknolojisi ProgramÄ±
>> 27700-Nizip-Gaziantep/TÃ¼rkiye
>> ayildirim at gantep.edu.tr
>> > -----------!!!----!!!!
>> > Not sure for what this D stands here. I discarded it in the example
>> > below. Also you have a spurious backslash. So you could write your
>> > equation as
>> >
>> > D[M[r, t], t] == D[M[r, t], r, r] + 2/r D[M[r, t], r] - k M[r, t]
>> >
>> >> Boundary conditions are:
>> >>
>> >> 1-) at t=0, M= Mo
>> >
>> > M[r, 0] == M0
>> >
>> >> 2-) r = 0, dM/dr=0
>> >
>> > D[M[0, t], t] == 0
>> >
>> >> 3-) at r = R, M = Ms
>> >
>> > M[R, t] == Ms
>> >
>> > Then you can use DSolve or NDSolve as in
>> >
>> > DSolve[{D[M[r, t], t] ==
>> > D[M[r, t], r, r] + 2/r D[M[r, t], r] - k M[r, t], M[r, 0] == M0,
>> > D[M[0, t], t] == 0, M[R, t] == Ms}, M, {r, t}]
>> >
>>
>>
>>
>
>
> Regards,
> -- Jean-Marc
>
Prev by Date:
**Re: Convert funcion**
Next by Date:
**Problem/bug with ends of thick lines in graphics**
Previous by thread:
**Re: partial differential equation of diffusion**
Next by thread:
**Fit data with range**
| |