laminar flow

n.
Nonturbulent flow of a viscous fluid in layers near a boundary, as that of lubricating oil in bearings.

A smooth, streamline type of viscous fluid motion characteristic of flow at low-to-moderate deformation rates. The name derives from the fluid's moving in orderly layers or laminae.

The chief criterion for laminar flow is a relatively small value for the Reynolds number, Re = ρVL/μ, where ρ is fluid density, V is flow velocity, L is body size, and μ is fluid viscosity. Laminar flow may be achieved in many ways: low-density flows as in rarefied gases; low-velocity or “creeping” motions; small-size bodies such as microorganisms swimming in the ocean; or high-viscosity fluids such as lubricating oils. At higher values of the Reynolds number, the flow becomes disorderly or turbulent, with many small eddies, random fluctuations, and streamlines intertwining. See also Creeping flow; Reynolds number; Turbulent flow; Viscosity.

Nearly all of the many known exact solutions of the equations of motion of a viscous fluid are for the case of laminar flow. These mathematically accurate descriptions can be used to give insight into the more complex turbulent and transitional flow patterns for which no exact analyses are known. See also Navier-Stokes equation.

The theory of viscous lubricating fluids in bearings is a highly developed area of laminar flow analysis. Even large Reynolds number flows, such as aircraft in flight, have regions of laminar flow near their leading edges, so that laminar flow analysis can be useful in a variety of practical and scientifically relevant flows. See also Antifriction bearing; Boundary-layer flow; Fluid flow; Lubricant.

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A type of non- turbulent flow where the movement of each part of the fluid (gaseous, liquid, or plastic) has the same velocity, with no mixing between adjacent ‘layers’ of the fluid. It may be seen at low velocities in a smooth, straight river channel, and at some glacier snouts. Compare with turbulent flow.

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fluid flow; streamline flow

The smooth flow of a fluid in which adjoining layers of the fluid flow parallel to one another. During laminar flow, all the fluid particles move in distinct and separate layers; there is no mixing between adjacent layers. Compare turbulent flow.

Laminar flow

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