y plus
 

hello, using a k-e model for a basin with roughly 100x40x3m, and a very low inlet velocity (<1m/s), the solver gives me a reynolds number of 10^5!! the y plus also goes up to 1000 or greater for 50% of the cells. Is there an explanation for this? Is this ok? or should i refine the mesh even more? i have already about 85000 elements. Any comments? Thanks!

Re: y plus
 

you may calculate Re with hand calculation as well. The absolute velocity is not an indicator of yplus. Yplus depends on your Reynolnds number. For your case, a grid cell with 0.1% of the domain size, perpendicular to flow direction, should resolve your boundary layer up to yplus of 1-10. 50% cells above yplus 1000 seems to be ok but it depends on your grid and Re. it is difficult to comment on this number.

VK

Re: y plus
 

Hi Icm,

Do a mesh size sensitivity study and find out. For some flows that y+ is OK and for some it is not.

Regards, Glenn

Re: y plus
 

If you're using the k-e model, then there's no point in having a yplus < 11 as the model uses wall functions to model the sublayer. Just make sure you have 10 elements in the boundary layer for good resolution.

Adam