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Turbulence and Shear Flow Phenomena -1 First International Symposium

ISBN:
1-56700-135-1 (Print)

ON THE USE OF LARGE-SCALE VORTICAL STREAMWISE STRUCTURES TO CONTROL TURBULENCE IN CHANNEL FLOW

Alfredo Soldati
Centro Interdipartimentale di Fluidodinamics e Idraulica, Dipartimento di Energetica e Macchine, Universita degli Studi di Udine, Via delle Scienze 208, 33100 Udine, Italy

Marco Fulgosi
Centro di Fluidodinamica e Idraulica and Dipartimento di Scienze e Tecnologie Chimiche Universita degli Studi di Udine, Udine, 33100, Italy

Sanjoy Banerjee
Department of Chemical Engineering University of California at Santa Barbara, Santa Barbara, California, 93106

Abstract

We analyzed the influence of large-scale ElectroHydroDynamic streamwise vortical flows superim-posed to a plane Poiseuille flow. The vortical flows had a spanwise periodicity of 340 wall units, in order to encompass three low-speed streaky structures. Results indicate that, after the actuation of control flows, the flow field undergoes an initial steep transient of about 600 shear-based time units with a moderate drag decrease (about 6 − 7%), followed by a steady-state in which the overall drag was only slightly affected by the EHD flows. Higher intensity cases led to drag reduction. The long-term effect of flow control is small, being at most about 4 − 5%. Corresponding to such small modification of the overall drag there is no significant change in the structure of turbulence at the wall.