**1. n. []**

A type of streamlined flow for single-phase fluids in which the fluid moves in parallel layers, or laminae. The layers flow smoothly over each other with instabilities being dampened by the viscosity. Laminar flow occurs in straight pipes when the Reynolds number is below a critical value, corresponding to a low production rate. Above this value, the flow is turbulent. For laminar flow in straight pipes, the velocity profile across the pipe is parabolic, increasing from zero at the wall of the pipe to a maximum at the center equal to twice the mean velocity.

**See:**
flow regime

**2. n. []**

The flow of a viscous fluid in which the fluid moves in parallel layers with a fixed velocity gradient from the centerline to the containing walls of the conduit. Sometimes referred to as streamline flow. It occurs at a low Reynolds number, a dimensionless term related to fluid viscosity and flow rates.