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.

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

Still having a confusion in the grad(u) or without grad(U)
 

Hello,


I still have a doubt with the fvSchemes in the OpenFoam. What is the difference if I am using the

div(phi,k) Gauss Upwind grad(k);
or

div(phi,k) Gauss Upwind;


Similarly for other variables. I had gone through the thread suggested, but was not able to understand it clearly.


Many thanks for any help.