High derive values
Posted: Wed Feb 20, 2013 11:27 pm
Hi all,
i'm running steady state MRF simulations (so 2 volume coupled) with saturne, some of them don't reach convergence and diverge easily.
My approach is :
Prepare mesh -> run few iterations with k-eps (i'm using air inside an oven) with scalable wall function -> check y+
if it's too big ( >300) -> remesh with finer elements at the wall where y+ is high -> check again with few iterations and if necessary rmesh again
if in the first iterations (10-15) y+ seems to be ok but then velocity increase a lot until divergence -> relaxation 0.5.
Often this doesn't help a lot... i would like to set relaxation = 0.01 but then pressure relax = 0.99 (1-0.01) so it's not helpful.
And again the derive values are very high (> e+6 ).
What can i do as strategy? How can go further in analising my mesh/simulation?
I'm quite a newbie of cfd so i would like all of your suggestions !!
Thank you
Andrea
i'm running steady state MRF simulations (so 2 volume coupled) with saturne, some of them don't reach convergence and diverge easily.
My approach is :
Prepare mesh -> run few iterations with k-eps (i'm using air inside an oven) with scalable wall function -> check y+
if it's too big ( >300) -> remesh with finer elements at the wall where y+ is high -> check again with few iterations and if necessary rmesh again
if in the first iterations (10-15) y+ seems to be ok but then velocity increase a lot until divergence -> relaxation 0.5.
Often this doesn't help a lot... i would like to set relaxation = 0.01 but then pressure relax = 0.99 (1-0.01) so it's not helpful.
And again the derive values are very high (> e+6 ).
What can i do as strategy? How can go further in analising my mesh/simulation?
I'm quite a newbie of cfd so i would like all of your suggestions !!
Thank you
Andrea