Rotating turbulence evolving freely from an initial quasi 2D state

Recent experiments demonstrated the existence of quasi-twodimensional turbulence in a boundary-forced fluid system subjected to strong rotation. The principal results are briefly recalled and an inertial wave mechanism is proposed as an explaination for the observed sudden transition from 3D turbulence to a quasi-twodimensional turbulent flow. The main contribution of the paper is however concerned with the freely evolving state, obtained when the forcing is suddenly stopped. Experiments show an increase in time of the turbulence length scale, indicating an inverse energy flux. These observations are analysed in terms of a similarity theory derived for evolving turbulence with Ekman friction. The scale increase is by pairing of vortices of like sign and by large scale unsteady meandering motions.