Flow (fully dev)

1. Oct 16, 2012

pyroknife

I have attached the problem.

I did the problem, but i'm not confident about my approach or solution. The "fully developed" part is confusing me a little, but anways here'smy approach:

For v=0.1 m/s
Reynold's number=(density)*(velocity)*diameter/viscosity
=1000*.1*0.02/(10^-3)=2000 <<<< I think this indicates that its laminar?
If so then:
L/d=.06*Reynold's
L=.02*.06*2000=2.4m

For v=10m/s
Reynold's=200,000 <<< I think this indicates that its turbulent
If so then:
L/d=4.4(Reynold's)^(1/6)
L=.02*4.4*(200000^(1/6))
=.673m

2. Oct 17, 2012

Staff: Mentor

Let me guess. You are trying to calculate the nominal entry length for flow in a tube. You
used the correct equations, and implemented them correctly (assuming you got the units right).

Fully developed flow means that the velocity distribution is not changing with time.