Finding root of a function

hjasak · May 7, 2008, 10:27

Dear All,

I have just implemented root-finding operations of a function f(x) = 0. If someone is interested, have a look at the SVN - it currently lives in the ODE library.

Enjoy,

Hrv

ngj · July 15, 2008, 08:25

Hi

I am about to be solving 4 sets of non-linear equations on each face on certain boundary-patches. As far as I can see, the function implemented by Hrv is for 1 equation!?!
Is there anywhere in OF implemented some kind of solver for N non-linear set of equations?
If not, could you please suggest to me a suitable open-source implementation, preferable in C++.

Best regards,

Niels

P.S. Thank you for an utterly fantastic workshop.

sabago · June 1, 2015, 16:05

Dear all,

Has anyone been able to use the BisectionRoot, or RiddersRoot or the NewtonSecant methods in the "findRoot" folder on the svn?

Say I want to solve for x in

0 = -3 + 4(Exp(2x)-Exp(3x))

I have the findRoot folder in src/ODE and added the path to my /make for the solver.

How, then do I implement any of the findRoot methods to get x?

Best regards,
Sandra

sabago · November 1, 2015, 12:23

I fixed my issue on this link : http://www.cfd-online.com/Forums/ope...ng-method.html

Quote:

Originally Posted by sabago

Dear all,

Has anyone been able to use the BisectionRoot, or RiddersRoot or the NewtonSecant methods in the "findRoot" folder on the svn?

Say I want to solve for x in

0 = -3 + 4(Exp(2x)-Exp(3x))

I have the findRoot folder in src/ODE and added the path to my /make for the solver.

How, then do I implement any of the findRoot methods to get x?

Best regards,
Sandra

Saideep · August 10, 2016, 11:16

Hi guys;

I guess my post is best fitted to this thread.

I am trying to solve 2 non-linear equations simultaneously using Newton-secant method.

As Niels had asked the "findRoot" is tested over one equation. How can I couple and use two equations in order to find the solution roots? Any example case already implemented in Foam-extend?

Additionally is it possible to write the number of iterations taken in order to reach the tolerance?

Thanks,
Saideep

May 7, 2008, 10:27	Finding root of a function	#1
hjasak Senior Member Hrvoje Jasak Join Date: Mar 2009 Location: London, England Posts: 1,905 Rep Power: 33	Dear All, I have just implemented root-finding operations of a function f(x) = 0. If someone is interested, have a look at the SVN - it currently lives in the ODE library. Enjoy, Hrv sabago likes this. __________________ Hrvoje Jasak Providing commercial FOAM/OpenFOAM and CFD Consulting: http://wikki.co.uk

July 15, 2008, 08:25	Hihttp://www.cfd-online.com/Op	#2
ngj Senior Member Niels Gjoel Jacobsen Join Date: Mar 2009 Location: Copenhagen, Denmark Posts: 1,900 Rep Power: 37	Hi I am about to be solving 4 sets of non-linear equations on each face on certain boundary-patches. As far as I can see, the function implemented by Hrv is for 1 equation!?! Is there anywhere in OF implemented some kind of solver for N non-linear set of equations? If not, could you please suggest to me a suitable open-source implementation, preferable in C++. Best regards, Niels P.S. Thank you for an utterly fantastic workshop. __________________ Please note that I do not use the Friend-feature, so do not be offended, if I do not accept a request.

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June 1, 2015, 16:05		#3
sabago Member Sandra Join Date: Oct 2014 Posts: 58 Rep Power: 11	Dear all, Has anyone been able to use the BisectionRoot, or RiddersRoot or the NewtonSecant methods in the "findRoot" folder on the svn? Say I want to solve for x in 0 = -3 + 4(Exp(2x)-Exp(3x)) I have the findRoot folder in src/ODE and added the path to my /make for the solver. How, then do I implement any of the findRoot methods to get x? Best regards, Sandra

August 10, 2016, 11:16		#5
Saideep Senior Member Saideep Join Date: Apr 2015 Location: INDIA Posts: 203 Rep Power: 12	Hi guys; I guess my post is best fitted to this thread. I am trying to solve 2 non-linear equations simultaneously using Newton-secant method. As Niels had asked the "findRoot" is tested over one equation. How can I couple and use two equations in order to find the solution roots? Any example case already implemented in Foam-extend? Additionally is it possible to write the number of iterations taken in order to reach the tolerance? Thanks, Saideep