how to change the y+ value
 

HI,

I need to change the y+ value more smaller, how could I do it?

Thanks in advance

Place the first grid point closer to the surface

Dear Lefteris,

thanks for your quick reply, do you mean I need to minimize the spacing of the edage which is near the wall?

And when I adapt the y+value, and set the value, but when I xy-plot it, it is still larger than 1. Do you know why?

Yeap, minimise this edge by placing the first grid point as close to the wall as possible (as close as you need actually).
I don't really understand what you mean when you say "when I xy-plot it" (you mean you plot y+ ?) but y+ depends upon other parameters as well which you can only estimate beforehand and know their value only after the computations are completed.

Well, thanks, I do just you said, the aspect ratio has also beed reduced, but the y+ value on the right wall, it is still 9.

Do I need to creat a iso-surface that near the wall, or just choose the wall surface? If I need, which one do I need to keep surface constant?

One more problem, we have been a experimental data to compare, but the velocity from the xy-plot are not very close to the experimental one. Do you kown why?

Best regards

If y+ = 9 and you want it to become y+=1 you need to make the first cell about 9 times finer than in your current grid.
In Fluent, you just need to plot y+ on the surface. It will use the first cell height for that!
For the last question you need to show us more about your setup / grid / settings and so on.

IS that mean I need to refine it in ICEM in 'refinement'-level 9? IS that right? or need to minimize spacing 9 times smaller

I am not sure what "refinement level 9" means. But if your first cell height is 1mm now, you need to reduce it to about 0.11mm.

y+
 

hi
change your mesh near the wall as small as you can and after check this parameter.

hi
use this tool to specify your mesh geometric parameters before your first calculation ,and i think there isn't an effective way to adjust your mesh (all y plus values) to the just condition.
http://geolab.larc.nasa.gov/APPS/YPlus/