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Offline Novice  
#1 Posted : 10 July 2017 21:54:49(UTC)
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Hi
I need a help for "FindRoot" function.(See attached file)

Also I got an error sample file(Inst_Colebrook_pipe_data.sm) which was downloaded from this forum.

Please, guide me to solve this error.

Novice

FindRoot_test_0.sm (41kb) downloaded 12 time(s).
Inst_Colebrook Pipe Data.sm (61kb) downloaded 11 time(s).Findroot_error.PNG

Edited by user 10 July 2017 22:03:29(UTC)  | Reason: Not specified

Offline Davide Carpi  
#2 Posted : 12 July 2017 01:19:08(UTC)
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Hello Novice Offline

An important thing is that Q1 must be undefined while you define the system of equations - and as for now even when you call FindRoot; there is a buil-in function Clear(...) for this.

Secondly as for now when there are numerical functions involved in the evaluation of the unknowns this plugin has issues (in this case the issue is in if(f(Q1), that can be replaced by cases(...), however the algorithm then fails to solve for the given initial guess);

FindRoot_test_0.sm (39kb) downloaded 12 time(s).

I'm working to improve both these things.

Edited by user 12 July 2017 01:43:22(UTC)  | Reason: Not specified

Best regards,

Davide

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thanks 1 user thanked Davide Carpi for this useful post.
on 12/07/2017(UTC)
Offline Jean Giraud  
#3 Posted : 12 July 2017 16:09:15(UTC)
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Originally Posted by: Novice Go to Quoted Post
Please, guide me to solve this error.


You MUST draw the diagram first !
Get inspired from NDTMA Collab [Colebrook Node].

Comments:

1. The "GivenFind" solver does not necessarily solves.
I have recollection solving for 22 variables in Mathcad 11.
It was necessary to constrain some variables, and this was
possible from some existing models, in fact: just refining
within the "solvability" of the system.

2. You have 7 'Q' indexed: that's not viable.
Instead: Q1, @2, Q3, ... Q7

3. Please rework the project to ease reading/understanding.

Jean

Inst_Colebrook MOODY.sm (22kb) downloaded 8 time(s).
Inst_Colebrook Pipe Data.sm (60kb) downloaded 6 time(s).
Solve Given_Find [UN Frobenius C1, C2].sm (72kb) downloaded 6 time(s).
FindRoot_test_0 Revisit.sm (42kb) downloaded 7 time(s).
Inst_Colebrook Pipe Data [Solve Node Flow].sm (150kb) downloaded 8 time(s).
Inst_Colebrook.sm (192kb) downloaded 6 time(s).
Inst_Colebrook.sm (192kb) downloaded 6 time(s).
Offline Novice  
#4 Posted : 15 July 2017 13:56:58(UTC)
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Dear Jean,

Thank you very much for your advice and examples
It is helpful to me.

Thank you!

MS
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