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IgorBraz1-Visitor
1-Visitor
May 12, 2020
Question

Non linear coupled differential equation system

  • May 12, 2020
  • 5 replies
  • 3001 views

Hi, can anynone help me please?!

 

I'm trying to solve this sistem of two couple differential equations but I'm not getting sucess. (I guess that the error is in the red highlighted in the second equation)

5 replies

L
LucMeekes23-Emerald IV
23-Emerald IV
May 12, 2020

I don't think you can use a derivative in the function vector for a differential system solver.

You may need to expand the vector with one more element.

 

Success!
Luc

I
IgorBraz1-VisitorAuthor
1-Visitor
May 12, 2020

Hi LucMeekes, thanks for your answer.

 

But how to expand the vector? The problem have two defree of freedom, I don't know how to expand the vector using Rkfixed comand

A
AlanStevens19-Tanzanite
19-Tanzanite
May 12, 2020

I can't see your Prime file, but judging by the PNG file, you need to do something like the following:

 

g0.jpg

(for "exolicit" read "explicit" !!!)

 

Alan

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LucMeekes23-Emerald IV
23-Emerald IV
May 12, 2020

Hi Alan,

 

attached is the OP's file for Prime2.

I had to zip it, because the forum is running stupid again.

 

Luc

A
AlanStevens19-Tanzanite
19-Tanzanite
May 13, 2020

Thanks Luc,

 

Attached is my Prime 2 working version (no idea if the results make sense or not!!)

 

g0.JPGg1.JPGg2.JPG.

 

Alan

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