Section: STEM · EngineeringDifficulty: Medium
Reynolds Number
USUK
A dimensionless number predicting whether fluid flow is laminar or turbulent.
Also: Re · Reynolds Re
Definition
The Reynolds number is a dimensionless quantity in fluid mechanics that predicts whether fluid flow will be laminar (smooth and orderly) or turbulent (chaotic), calculated as the ratio of inertial forces to viscous forces. Low Reynolds numbers indicate laminar flow; high numbers indicate turbulent flow. It is critical in designing pipes, aircraft, ships, and any system involving fluid movement.
Example
“Aerospace engineers calculate the Reynolds number for air flowing over a wing at different altitudes and speeds to predict whether the boundary layer remains attached (laminar) or breaks up (turbulent), which dramatically affects lift and drag.”
Synonyms
- Re number
- flow regime indicator
- inertia-viscosity ratio
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Related Terms
- Fluid Dynamics
- Laminar Flow
- Turbulent Flow
- Navier-Stokes Equations