Nonlinear dynamics of large-scale vortex structures in a turbulent Ekman layer

Nonlinear regimes of roll structure development in the Ekman atmospheric boundary layer are considered. Within the framework of a turbulent boundary layer theory that takes the inherent helicity into account, the helicity effect on the stability and development of secondary vortices is studied. The stabilizing role of helicity in the Ekman layer dynamics is detected. With increasing nonlinearity the rolls become time-dependent self-oscillatory structures exchanging energy and helicity with the main flow. Multi-scale structure regimes are obtained, similar to those observable in the atmospheric boundary layer and the solitary vortex structures previously discovered in bench and numerical experiments for Ekman flows between disks rotating in opposite directions.