# Numerical schemes for grad and div

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 October 15, 2012, 05:29 Numerical schemes for grad and div #1 Senior Member     Tobias Holzmann Join Date: Oct 2010 Location: Leoben (Austria) Posts: 1,519 Blog Entries: 6 Rep Power: 27 Hello Foamers, I have a question to some schemes in OpenFOAM. grad-Scheme - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - What is the differences between Code: ```grad(U) Gauss linear; grad(U) cellLimited Gauss linear 1;``` Its clear that I use a limiter for the grad schemes. But does that mean, that the change of U^{n-1} to U^n is limited? Is my interpretation correct? div-Scheme - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - Whats the difference between Code: ```div(phi, Z) Gauss limitedLinear 1 0 1 div(phi, Z) Gauss limitedLimitedLinear 1 0 1``` I think the first scalar is for the limiter. 1=full limiter 0=non limiter. The values after that are bouding parameters? so that the variable Z is bounded between [0-1] ? is that correct? And the differences between both? Any suggestion would be very nice. Regard Tobi immortality likes this.

 February 27, 2013, 11:38 #2 Senior Member     Ehsan Join Date: Oct 2012 Location: Iran Posts: 2,209 Rep Power: 19 hi can anyone answer to these questions? thanks.

 March 11, 2013, 17:10 #3 Senior Member     Tobias Holzmann Join Date: Oct 2010 Location: Leoben (Austria) Posts: 1,519 Blog Entries: 6 Rep Power: 27 Hi all, results of different schemes can be found on my homepage (its unfortunatelly german but with graphics) http://www.holzmann-cfd.de/index.php...rische-schemen sylvester, ngj and fabian_roesler like this.

 March 11, 2013, 17:31 #4 Senior Member   Niels Gjoel Jacobsen Join Date: Mar 2009 Location: Deltares, Delft, The Netherlands Posts: 1,702 Rep Power: 27 Hi Tobias, Nice graphics Just a quick question from a non-German speaking person. Is it a pure advection problem, which you have been solving? At least with a quick view on a couple of the cases, it seems that you are only changing the divergence scheme. Thanks, Niels

 March 11, 2013, 17:41 #5 Senior Member     Anton Kidess Join Date: May 2009 Location: Delft, Netherlands Posts: 1,150 Rep Power: 20 Niels, indeed the site states pure convection ("reine Konvektion"). ngj likes this. __________________ *On twitter @akidTwit *Spend as much time formulating your questions as you expect people to spend on their answer. *Join the OpenFOAM stackexchange Q&A site: http://area51.stackexchange.com/prop...oHPxcPqde7HtA2

 March 11, 2013, 17:45 #6 Senior Member     Tobias Holzmann Join Date: Oct 2010 Location: Leoben (Austria) Posts: 1,519 Blog Entries: 6 Rep Power: 27 Hi, yes I am only changing the div schemes to get influence of konvection influence ... "there is no diffusivity". That s necessary to get see what influence the different schemes are make in the equations. ngj likes this.

 March 11, 2013, 22:24 #7 Member   Dan Kokron Join Date: Dec 2012 Posts: 33 Rep Power: 5 I found the following paper that includes some other results along the same lines as Tobi. The paper includes the step function and two other shapes. http://powerlab.fsb.hr/ped/kturbo/Op...GammaPaper.pdf Dan

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