i´am simulating flow forces on a spool in hydraulic valve with cfdesign (blue ridge numerics)

so i have problems with the validation of my results!

cfdesign is using in the k-eps-model wall functions to simulate the turbulent flow next to a wall

can somebody explain to me how the Y+ Value works and why ?

e.g.

-> what happen if the values outside the range given by cfdesign (35 < y+ < 350)

-> Y+ values to low: should i unrefine the mesh, which variables are under- or overpredicted

-> Y+ values to high: refine the mesh?

-> etc.

mfg

Matthias

i suggest you look at schlichting's book 'boundary layer theory'. you get (a)idea about y+ ,(b)the derivation for wall region in terms of y+ and (c) assumptions for wall shear etc., used in the derivation. one shoud go preferably for remeshing (depending on the wall treatment) at the near wall region. some caution, in terms of meshing, should be exersised to address the vicinity of the near wall region, i.e., the wall law region to the fully developed one.