#### 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.