$\frac{\pi r^4 \Delta P}{8 \eta L}$

$2 imes \frac{\pi r^4 \Delta P}{8 \eta L}$

$\frac{\pi r^4 \Delta P}{16 \eta L}$

$\frac{\pi (2r)^4 \Delta P}{8 \eta L}$

Turbulent

Laminar

Compressible

Supersonic

Airflow through the trachea

Water flowing down a river

Blood flow through a capillary

Ocean currents

Fluid flows in a chaotic and turbulent manner.

Fluid flows in smooth, parallel layers.

Fluid velocity is constant across the tube's cross-section.

Fluid pressure is constant along the length of the tube.