This is an animation of a numerical simulation, where a passive tracer
is transported by the flow inside a cuboid domain with free outflow
boundary conditions (except for the inlet boundary, which is a "solid
wall" with a laminar jet flowing out of it). Turbulent dynamics
develop spontaneously from a laminar initial condition. The inlet
boundary condition is laminar and constant in time. Arrows display the
velocity of the flow, while the tracer is shown as a black "smoke".
For viewing convenience, the first video does not display the velocity
field (so that the simulation looks like an experiment).