ABSTRAKT

Direct numerical simulations (DNSs) of a homogeneous shear flow are performed to study the detailed mechanism of the tilting of a longitudinal vortical structure typically observed in a turbulent shear flow. The longitudinal vortical structure, having the intense streamwise vorticity, is elongated in the streamwise direction, though it is also tilted in the spanwise direction. The sense of this tilting is determined by the sense of the streamwise vorticity. Although it is known that the tilting is due to the combined effects of the non-linear terms and mean spanwise vorticity, its detailed mechanism is still unknown. By systematically changing the Reynolds number of the flow as well as imposing a spanwise system rotation, we investigated the effects of the non-linear term and spanwise rotation on the tilting.