Dimensionless wall distance (y plus)
A non-dimensional wall distance for a wall-bounded flow can be defined in the following way:
is often refered to simply as y plus and is commonly used in boundary layer theory and in defining the law of the wall.
Estimation of y plus
The following online tools can be used to estimate the necessary grid spacing in order to obtain a desired y plus:
- Another y+ estimation script by CHAM. Uses a slightly different approximation formula but also works great.