1. Flow regimes

In real fluid flow, there are two main types of behavior. Each characterizes a specific flow regime: laminar and turbulent.

Fluid flow is said to be laminar when it is strictly steady, or when the velocity field evolves in a continuous, ordered manner as a function of time and space. For a real fluid flow of this kind, the velocity may have a variable intensity in a straight section due to viscosity. Velocity is zero for particles in contact with any immobile material surface and maximum for the furthest points. In this type of steady-state flow, the trajectories (which are then merged with the streamlines) never intersect during the course of the flow (figure 1 ).