Laminar flow

The fluid flows in layers that do not mix with each other. In this case, the flow is usually steady (at constant flow velocity).

The Reynolds number Re is used as an evaluation criterion.

This is defined as follows: Re:=c⋅l / ν=c⋅l⋅ρ / μ,

where c is the magnitude of a characteristic flow velocity, l is a characteristic length, ν is the kinematic viscosity or μ (or also η) is the dynamic viscosity, and ρ is the density of the flowing fluid.