# Homework Help: How do I calculate y+ in fluid mechanics from the relation y+=(ut*y)/v?

1. Aug 23, 2011

### firestarter7

1. The problem statement, all variables and given/known data
I am trying to calculate y in the relation y+=(ut*y)/v where y+ is similar to a local Reynolds number, so its magnitude can be expected to determine the relative importance of viscous and turbulent processes. In the listed relation ut is the friction velocity [ut=sqrt(wall shear stress/density)] and v is the viscosity. The problem I am facing is that I don't know what y+ to choose to calculate y, my ultimate goal is thus to calculate y, and I am not sure if I should only assume a y+ so I can calculate y. If so, on what basis should I choose y+? Thanks.

3. The attempt at a solution
I did assume y+ and solved for y, but that just does not make sense. I am confused as I am only trying to calculate the laminar boundary layer y, on a flat plate according to Blasius procedures.