About the Use of Crank Nicholson scheme

And · November 19, 2009, 08:11

Hello OpenFOAM community,

I'm working on LES of turbulent channel flow and so I'm deeply interested in your discussions and in particular on the validation on the OpenFOAM results.

As I'm concerned in the study of both spatial than temporal discretizations OpenFOAM schemes for LES, my doubt is if selecting the flag CrankNicholson in ddt schemes would mean the correct use of such scheme as in the FOAM ProgrammersGuide P-43 it is said that:

"The Crank Nicholson scheme can be implemented by the mean of implicit and explicit terms:

solve
(
fvm::ddt(phi)
==
kappa*0.5*(fvm::laplacian(phi) + fvc::laplacian(phi))
)
".

If is this so, I'have to rewrite the left hand side of the corresponding UEqn.H exploiting both fvm and fvc operator in order to implement the Crank Nicholson scheme. Otherwise I would not have an effective Crank Nicholson time integration schemes and consequently losing the second order time accuracy.

Any hints about that

Regards

Andrea

Houthuys · November 14, 2017, 13:25

I've exactly the same question. Can someone answer this one?

November 19, 2009, 08:11	About the Use of Crank Nicholson scheme	#1
And New Member Andrea Aprovitola Join Date: Nov 2009 Posts: 16 Rep Power: 17	Hello OpenFOAM community, I'm working on LES of turbulent channel flow and so I'm deeply interested in your discussions and in particular on the validation on the OpenFOAM results. As I'm concerned in the study of both spatial than temporal discretizations OpenFOAM schemes for LES, my doubt is if selecting the flag CrankNicholson in ddt schemes would mean the correct use of such scheme as in the FOAM ProgrammersGuide P-43 it is said that: "The Crank Nicholson scheme can be implemented by the mean of implicit and explicit terms: solve ( fvm::ddt(phi) == kappa0.5(fvm::laplacian(phi) + fvc::laplacian(phi)) ) ". If is this so, I'have to rewrite the left hand side of the corresponding UEqn.H exploiting both fvm and fvc operator in order to implement the Crank Nicholson scheme. Otherwise I would not have an effective Crank Nicholson time integration schemes and consequently losing the second order time accuracy. Any hints about that Regards Andrea

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November 14, 2017, 13:25		#2
Houthuys New Member rik houthuys Join Date: Jan 2017 Posts: 27 Rep Power: 9	I've exactly the same question. Can someone answer this one?