Viscous sublayer thickness
 

Hallo All

I have seen in the literature that the thickness of the viscous sublayer in a fully developed flow is approx. y+ = 10. But is there any equation for the thickness as a function of the distance from a pipe inlet??

Regards

Bo

PS.: I know this i snot a Fluid Mechnics Forum - is there one where I could ask instead??

Re: Viscous sublayer thickness
 

I don't know the answer to your question, but you are definitely in the right place here. You can also try www.efluids.com which also has a discussion board. I believe you have to register first though.

Re: Viscous sublayer thickness
 

Hej Bo' :)

Have you checked the book by schlichting, (not sure if it is spelled correct don't have the book on my desk) boundary layer theory. There exist news groups with fluid mechanics, sci.mech.fluids and some other relevant sci.geo.fluid sci.physics.computational.fluid-dynamics

Regards Jan

Re: Viscous sublayer thickness
 

Here is a crude way to estimate. This is based upon flat plate theory:

for a y+ value of 10 you are right at the begining of what is known as the log region in the wall law plot.

yu*/nu=y+ u*=sqrt(cf/2)Ue cf=.664/sqrt(Rex) Rex=(rho*V*x)/Nu

Ue = edge velocity rho=density nu=viscosity x=length downstream of the entrance.

Does there exist a rule or a law how many boundary layers should be built to model the viscous sublayers?
I can only find the dimensionsless wall distance. But there is no information about how many layers are required.

Best Regards,
tH3f0rC3