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-   -   Excel like goal-seek type functionality in OpenFOAM (http://www.cfd-online.com/Forums/openfoam/75623-excel-like-goal-seek-type-functionality-openfoam.html)

benk April 30, 2010 16:02

Excel like goal-seek type functionality in OpenFOAM
 
This is a long shot, but is there an excel like goal-seek functionality in OpenFoam?

In one of my custom made solvers I have a non-linear algebraic equation and I need to iterate for a value inside the equation, like:

Val = [exp(b*a) + exp(-c*a)]

I know everything except a, which I want to find.

benk April 30, 2010 16:40

I guess I'm looking for a built in Newton's method in OpenFoam. It's fairly easy to implement actually (as long as the analytical derivative is known).

chegdan April 30, 2010 16:46

Root finding
 
Openfoam has a root finding method that I have never used but noticed while looking around in the source. Take a look at:

/OpenFOAM/OpenFOAM-1.5-dev/src/ODE/findRoot/BisectionRoot
and
/OpenFOAM/OpenFOAM-1.5-dev/src/ODE/findRoot/RiddersRoot

of course this is in your particular version, mine being the 1.5-dev type. You could also do some sort of newton-raphson type root finding or many others that are in the Numerical recipes books with:

lhs-rhs=0 and find the root of your function of a.

Hope this helps.

Dan

benk April 30, 2010 16:50

Interesting, I'll take a look at that. Thanks.


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