Y+ values in ANSYS/FLOTRAN
 

I had a chance to speak to one of the FLOTRAN developers on the issue of the recommendation of y+ values in the FLOTRAN manual. The manual states that y+ values up to 5000 can be used in a favorable pressure gradient. Some doubt was expressed in this forum

The recommendation comes directly from White's Viscous Fluid Flow book, section 6-4.1. Figure 6-9 shows the validity of wall laws by plotting experimental data for several flow types (separating, adverse, favorable). For strong favorable flows, the wall law is valid up to y+ vlaues of 5000.

The important point here is that you must evaluate your grid based on flow type. A general guideline that y+ should be less than 350 is not good for all situations.

This message is in response to an old post in this forum