Active control effectiveness and synchronization of wall turbulence under localized imposed unsteadinesss

Sedat F. Tardu (1) , Olivier Léon Doche (1)

1 LEGI - Laboratoire des Écoulements Géophysiques et Industriels [Grenoble]

The effect of a spatially localized time-periodic perturbation on the efficiency of suboptimal control of the wall turbulence is analyzed. It is shown that the imposed unsteadiness with a frequency in the median production range doubles the turbulent drag reduction under suboptimal control strategy. It is further observed that the spatially averaged turbulent wall shear is synchronized in time with the imposed perturbation waveform. This is related to the synchronization of the unstable periodic orbits present in the near-wall turbulence in connection with the regeneration cycle of turbulence producing coherent structures.

Mots clés: boundary layer turbulence; drag reduction; flow control; shear turbulence; synchronisation

Domaines: Mécanique des fluides [physics.class-ph]; Mécanique des fluides [physics.class-ph]

Sedat F. Tardu, Olivier Léon Doche. Active control effectiveness and synchronization of wall turbulence under localized imposed unsteadinesss. Physics of Fluids, 2007, 19 (108), pp.203-107. ⟨10.1063/1.2793157⟩. ⟨hal-00270777⟩