#### Entrance Length in Pipe Flow: Screencast

Introduces the concept of entrance length and boundary layer.

We suggest that after watching this screencast, you list the important points as a way to increase retention.

##### Important Equations:

\[Re = \frac{\rho U D}{\mu} = \frac{UD}{\nu}\]

where \(Re\) is the Reynolds number

\(U\) is the freestream velocity

\(\rho\) is the density of the fluid

\(\mu\) is the dynamic viscosity of the fluid

\(\nu\) is the kinematic viscosity of the fluid

\(D\) is the diameter of the pipe.

\[U= \frac{Q}{A}\]

where \(Q\) is the volumetric flow rate, and \(A\) is the cross-sectional area of the pipe.

\[\frac{l_{e,laminar}}{D} = 0.06Re\]

where \(l_{e,laminar}\) is the entrance length for laminar flow.

\[\frac{l_e,turbulent}{D} = 4.4Re^{\frac{1}{6}}\]

where \(l_{e,turbulent}\) is the entrance length for turbulent flow.