Laminar flow
Definition
Smooth, orderly fluid flow where the fluid moves in parallel layers that slide past each other without mixing — like syrup pouring in a steady stream.
Technical definition
Flow regime in which fluid particles move in smooth, parallel layers (laminae) with no disruption between them. Occurs at low Reynolds numbers (typically Re < 2300 in pipes), where viscous forces dominate over inertial forces.
Example
Smoke rising from a candle starts as a smooth laminar column, then breaks into chaotic swirls a few centimeters up. Blood flow in small healthy arteries is mostly laminar, which keeps resistance low.
Laminar does not mean slow and turbulent does not mean fast — what matters is the Reynolds number, which combines speed, size, density, and viscosity. Fast-flowing honey in a thin tube can be laminar, while slow air over a large wing can be turbulent.