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-   -   Newbie Navier Stokes Questions + Grid (http://www.cfd-online.com/Forums/main/10757-newbie-navier-stokes-questions-grid.html)

Jigar February 5, 2006 13:11

Newbie Navier Stokes Questions + Grid
 
hello

if i am running Navier Stokes for the entire 3d flow domain (near wall and far from walls), is the y+ value really an issue in this case?

Is doing a simple grid dependecy check enough for near wall regions???? (my problem is flow in a room so no Eulerian at is used at all)

my 2nd question:

if i use Power (Watts) as boundary conditions instead of Surface temperature for an object, is it true that the grid distribution near the object is not really important???


ag February 6, 2006 10:01

Re: Newbie Navier Stokes Questions + Grid
 
Your questions are not really independent. Grid resolution is important if you want to resolve the gradients that control the flow. If you don't care about the gradients then use whatever grid you want. If the velocity gradient near the wall (which is actually fairly important in most flows) is not an issue then y+ is unimportant. And regardless of what boundary conditions you use, you still need a good grid distribution near the object if you want to resolve the gradients in the flow field.

Jigar February 6, 2006 11:06

Re: Newbie Navier Stokes Questions + Grid
 
but Is doing a simple grid dependecy check enough for near wall regions???? to get grid convergence??

ag February 6, 2006 13:08

Re: Newbie Navier Stokes Questions + Grid
 
Generally speaking no, unless you have some method a priori that allows you to know that the solution is grid-independent away from the walls.

jigar February 6, 2006 13:14

Re: Newbie Navier Stokes Questions + Grid
 
the reason iam asking these questions, is because the software that i use (Airpak from Fluent Inc) does not have the capability to compute y+. It is for indoor air simulation, and uses Navier Stokes for the whole flow domain


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