Hi all,(adsbygoogle = window.adsbygoogle || []).push({});

I have learned that the hydrodynamic entrance length of a channel (to form fully developed laminar flow) is correlated to the Reynolds number, because the shear effects have to propagate inwards from the walls of the channel. However recently I found out that there is a 'minimum' to the dependence on the reynolds number, for example in Deen (Analysis of transport phenomena) I find for a cylindrical tube:

[tex]\frac{L_v}{R}=1.18+0.112 Re[/tex] with [tex]Re=\frac{2 U R}{\nu}[/tex]

With R the radius and [tex]L_v[/tex] the entrance length.

The Reynolds dependent term in this equation I can understand (and derive), but I do not know what effect is responsible for the 'offset'. Can anyone explain to me why this occurs?

Thanks in advance!

**Physics Forums | Science Articles, Homework Help, Discussion**

Dismiss Notice

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Hydrodynamic entrance length: independent of Re?

Can you offer guidance or do you also need help?

Draft saved
Draft deleted

**Physics Forums | Science Articles, Homework Help, Discussion**