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-   -   Why define a grad Scheme when using linearUpwind? (http://www.cfd-online.com/Forums/openfoam-pre-processing/103719-why-define-grad-scheme-when-using-linearupwind.html)

Benedikt June 25, 2012 04:19

Why define a grad Scheme when using linearUpwind?
 
Hello,
I have two question regarding the div Schemes. I set my div-Schemes like this:

div(phi,U) Gauss linearUpwind grad(U)

Could you tell me why I have to define a grad Scheme when using linear Upwind as a div Scheme? I don't see the diference between linearUpwind and upwind/QUICK which would explain the need for a gradient Scheme.

Second question:
I tried these:

div(phi,U) Gauss upwind
and:
div(phi,U) Gauss upwind grad(U)

Why can I define a grad Scheme after defining a div Scheme, what does it change?

Thanks for your help in advance.

florian_krause June 25, 2012 08:54

Quote:

Originally Posted by Benedikt (Post 368125)
Hello,
I have two question regarding the div Schemes. I set my div-Schemes like this:

div(phi,U) Gauss linearUpwind grad(U)

Could you tell me why I have to define a grad Scheme when using linear Upwind as a div Scheme? I don't see the diference between linearUpwind and upwind/QUICK which would explain the need for a gradient Scheme.

Second question:
I tried these:

div(phi,U) Gauss upwind
and:
div(phi,U) Gauss upwind grad(U)

Why can I define a grad Scheme after defining a div Scheme, what does it change?

Thanks for your help in advance.

Hi Benedikt,
the thread below might help you to understand why you need to specify a grad scheme when using linearUpwind and what the difference is between linearUpwind and upwind.

http://www.cfd-online.com/Forums/ope...tedlinear.html

Best,
Florian


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