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4-Participant

## Problems with odesolve: The Integral-System may have two solutions but odesolve find the wrong one

Hi everybody,

the integral-System I'ld like to solve do have more than one solution. Once odesolve found the right solution, but in the most cases the unphysical soltution is found. Do anybody know this Problem or has a idea how I can tell odesolve, that I'am searching the other solution ?

Big thanks to everybody who can help me.

David

7 REPLIES 7
23-Emerald I
(To:dahu)

@dahu wrote:

Hi everybody,

the integral-System I'ld like to solve do have more than one solution. Once odesolve found the right solution, but in the most cases the unphysical soltution is found. Do anybody know this Problem or has a idea how I can tell odesolve, that I'am searching the other solution ?

Big thanks to everybody who can help me.

David

4-Participant
(To:Fred_Kohlhepp)

the System of equations is very hughe. I have 5 Integral equations and 2 algebraic equations. Once a time odesolve found the right solution, but in the most cases odesolve finds the wrong solution. So I'm sure, that the System of equations isn't wrong because sometimes odesolve is doing right. But the most of the time it isn't so have you any idea how I can adapt the solve block or anything else to find the right solution everytime ?

24-Ruby V
(To:dahu)

You may add additional appropriate constraints in the solve block and see if that helps.

4-Participant
(To:Werner_E)

I added one initial condition  for each equation. Do yuo have any idea how to add more constraints than equations ? I tried this while adding an inequation and it doesn't work

24-Ruby V
(To:dahu)

> Do yuo have any idea how to add more constraints than equations ?

No. We don't see what you are doing, we don't know what kind of ODE you are dealing with. We don't know why you think that is has more than one solution and we don't know what the difference between the correct and the wrong solution may be.

Sorry, but our clairvoyant balls aren't that good 😉

I am not sure if we could help when you show your worksheet, but I am pretty sure we can't without more information. So I would advise that you attach your worksheet if possible. Because of a bug in the foum software you may have to zip it before you ar able to attach it here.

4-Participant
(To:Werner_E)

The problem is, that it isn't possible to show you the worksheet because I'm not allowed to. It is the Topic of my master thesis and their are some confidential informations. So I hopped that maybe anybody of you had the same problem in the past.

I knwo that their must be more than one solution, because sometimes mathcad is doing right. But in most of the time the solution is wrong, without changeing anything on the equations or the programm.

21-Topaz II
(To:dahu)

Oh, bye! give an example that is even remotely similar...........

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