The dynamics of transitional and turbulent flows is often dominated by organized structures with a life-time much longer than the characteristic time-scale of the surrounding small-scale turbulence. Organized structures may appear as secondary flows as a result of an instability, but they persist in turbulent flows. They manifest themselves as eddies or localized vortices and play an important role in, for example, mixing and transport processes. Although the existence of organized structures has been revealed by many experiments and by numerical simulations, they are somewhat elusive, as...

The dynamics of transitional and turbulent flows is often dominated by organized structures with a life-time much longer than a characteristic time scale of the surrounding small-scale turbulence. Organized structures may appear as secondary flows as a result of an instability but they persist in turbulent flows. They manifest themselves as eddies or localized vortices and play an important role in e.g. mixing and transport processes. Al though the existence of organized structures has been revealed by many experiments and by numerical simulations they are somewhat elusive, as there is no...