An Easy Way to Understand Laminar Flow vs. Turbulent Flow

Image courtesy of
Laminar flow occurs when a fluid flows in parallel "layers" with no interaction between the layers. When flowing at low velocities, fluids tend to flow without lateral (sideways) mixing, and adjacent layers glide past one another, analogous to playing cards sliding between others in a deck.

In contrast to laminar flow, turbulent flow, caused by excessive kinetic energy in parts of a fluid flow, undergoes mixing and lateral irregularities characterized by eddies, recirculation, and apparent randomness. Fluid speed magnitude and direction changes chaotically in turbulent flow.

The video below provides a very simple, but very effective, demonstration of laminar and turbulent flow.