In 1883, Osborne Reynolds expanded the results of the experiments of Darcy and defined the ``critical velocity''. Darcy's experiments were based on laminar flow, the movement of fluid essentially in parallel lines when viewed on a macroscopic scale. Critical velocity defines the transition between laminar flow and turbulent flow where fluid moves in irregular and rotational paths. This transitional velocity is a dimensionless ratio named the Reynolds number and defines a range for the validity of Darcy's Law in turbulent flow. (Appendix B)
If the value of the Reynolds number, RE is:
¯ Darcy's Law is validpartially turbulent flow exists
Darcy's Law does not hold
turbulent flow
Darcy's Law does not hold