# Difference SFCD and GammaV

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 October 23, 2008, 05:52 Hello All and especially Prof. #1 New Member   Bart Boonacker Join Date: Mar 2009 Posts: 7 Rep Power: 9 Hello All and especially Prof. Jasak, I am currently working on my MSc thesis and I would like to know something; I cannot find any reference on the SFCD scheme and how it works. I can try to find out using the .C and .H, but my C++ knowledge does not extend that far I regret. 1) Does anyone have a reference or is anyone willing to share some thoughts/opinions about SFCD ? 2) Also, what is the main difference between SFCD and the Gamma scheme ? Please correct me if I'm wrong, Is the difference that the Gamma scheme contains a scaling factor (which is 2*beta_m in Jasaks paper(?)) and SFCD does not, or is it also in the blending function or other parts? Best regards, Bart immortality likes this.

 October 23, 2008, 07:28 Hello Bart, All these schem #2 Senior Member   Hrvoje Jasak Join Date: Mar 2009 Location: London, England Posts: 1,784 Rep Power: 22 Hello Bart, All these schemes are blended upwind-central type, using a limiter. The only true difference is the form of the limiter and its basis. The original reference for SFCD is a PhD from Dr. Harry Ziman, from mid 1990-s at Imperial College London. Basically, the limited looks like MINMOD and you can revrese-engineer it from the code: scalar phict = LimiterFunc::phict ( faceFlux, phiP, phiN, gradcP, gradcN, d ); scalar limitPhict = min(max(phict, 0), 0.5); return limitPhict/(1 - limitPhict); Here, phict is Phi-C-tilde (have a look at the Gamma paper) and the limiter is written out. For Gamma, the limiter is: min(max(phict/k_, 0), 1) but k is re-scaled on the constructor to be between 0 and 1 (in reality is is 0-0.5). k_ = max(k_/2.0, SMALL); Enjoy, Hrv Amir, 1/153 and immortality like this. __________________ Hrvoje Jasak Providing commercial FOAM/OpenFOAM and CFD Consulting: http://wikki.co.uk

 October 23, 2008, 09:08 Thanks for the quick clarifyin #3 New Member   Bart Boonacker Join Date: Mar 2009 Posts: 7 Rep Power: 9 Thanks for the quick clarifying awnser, I'll see if I can get a hold off Dr. Ziman's paper. What I don't get so far, k is equal to beta_m ? Then why is Phi-C-tilde limited ? Is the limiting done to easily select between UD, blending or CD, or something a like ?

 October 23, 2008, 09:36 @PhdThesis{Ziman:PhD, autho #4 Senior Member   Hrvoje Jasak Join Date: Mar 2009 Location: London, England Posts: 1,784 Rep Power: 22 @PhdThesis{Ziman:PhD, author = {Ziman, H.J.}, title = {A computer prediction for chemically reacting flows in stirred tanks}, school = {Imperial College, University of London}, year = {1990} } Yes, it's all about automaticaly blending UD and CD (well, a second-order scheme of your choice) . Hrv s.m likes this. __________________ Hrvoje Jasak Providing commercial FOAM/OpenFOAM and CFD Consulting: http://wikki.co.uk

 October 24, 2008, 09:12 Sorry, I do not do support wit #5 Senior Member   Hrvoje Jasak Join Date: Mar 2009 Location: London, England Posts: 1,784 Rep Power: 22 Sorry, I do not do support without a support contract. You simulation failed way before this point. Hrv __________________ Hrvoje Jasak Providing commercial FOAM/OpenFOAM and CFD Consulting: http://wikki.co.uk

December 2, 2010, 05:10
#6
Senior Member

Dr. Alexander Vakhrushev
Join Date: Mar 2009
Posts: 215
Rep Power: 11
Is SFCD a NVD scheme? Here it is states as a "General convection scheme"
How is it possible to understand from the OpenFOAM sources, is scheme TVD or NVD? I found only the directory structure:

Quote:
 Directories directory limitedSchemes directory multivariateSchemes directory schemes directory surfaceInterpolation directory surfaceInterpolationScheme
Regards,

Alexander
__________________
Best regards,

Dr. Alexander VAKHRUSHEV

Christian Doppler Laboratory for "Advanced Process Simulation of
Solidification and Melting"

Simulation and Modelling of Metallurgical Processes
Department of Metallurgy
University of Leoben

Franz-Josef-Str. 18
A - 8700 Leoben
Österreich / Austria
Tel.: +43 3842 - 402 - 3125
http://smmp.unileoben.ac.at

March 19, 2014, 18:07
#7
Senior Member

Join Date: Jan 2013
Posts: 310
Rep Power: 6
Dear Dr. Jasak,

1, what does k_ stand for in the code you mentioned?

2, about the limiter function for gamma scheme, did you have any reference for it? I did not find any information about it from the literatures?

3, this questions is not linked to Gamma scheme, but I ask here:
in openfoam, the numerical fluxes on the inter-cell face are for primitive variables (e.g. U_f) or conservative variables (e.g. (rho*U)_f)?

Thank you so much!

OFFO

Quote:
 Originally Posted by hjasak Hello Bart, All these schemes are blended upwind-central type, using a limiter. The only true difference is the form of the limiter and its basis. The original reference for SFCD is a PhD from Dr. Harry Ziman, from mid 1990-s at Imperial College London. Basically, the limited looks like MINMOD and you can revrese-engineer it from the code: scalar phict = LimiterFunc:hict ( faceFlux, phiP, phiN, gradcP, gradcN, d ); scalar limitPhict = min(max(phict, 0), 0.5); return limitPhict/(1 - limitPhict); Here, phict is Phi-C-tilde (have a look at the Gamma paper) and the limiter is written out. For Gamma, the limiter is: min(max(phict/k_, 0), 1) but k is re-scaled on the constructor to be between 0 and 1 (in reality is is 0-0.5). k_ = max(k_/2.0, SMALL); Enjoy, Hrv

 March 20, 2014, 12:51 #8 Senior Member   Join Date: Jan 2013 Posts: 310 Rep Power: 6 Dear Prof. Jasak, I have some understanding about the limiter for Gamma function used in Openfoam. But I found there is still some difference compared with your Gamma Scheme paper. The scalar k_ should be the constant beta_m in that paper. The difference is: Code: ```In the paper: if 0= 1, then central difference In OF2.1.1: if 0=1/K-, then upwind if 1/k_>= phict/k_ >= 1, then central difference``` Is what I am saying correct? Thank you for your any comments. OFFO

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