ABSTRACT
In laminar flow, individual particles of fluid follow paths that do not cross those of neighbouring particles. There is nevertheless a velocity gradient across the flow, and so laminar flow is not normally found except in the neighbourhood of a solid boundary, the retarding effect of which causes the transverse velocity gradient. Laminar flow occurs at velocities low enough for forces due to viscosity to predominate over inertia forces, and thus, if any individual particle attempts to stray from its prescribed path, viscosity firmly restrains it, and the orderly procession of fluid particles continues.
