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The Center for Control, Dynamical Systems, and Computation Winter 2010 Seminar Series and
 

Summary: The Center for Control, Dynamical Systems, and Computation
Winter 2010 Seminar Series and
The Center for Interdisciplinary Research in Fluid Physics
Presents
Downstream Traveling Waves: an Effective Means for
Preventing Transition to Turbulence
Mihailo Jovanovic - University of Minnesota
Friday, February 26, 2010, 3:00 4:00pm CHEM 1171
Abstract:
In this talk we assess the efficacy of a zero-net-mass-flux blowing and suction in the form of streamwise traveling
waves for transition control in a channel flow. It was recently shown that the net power balance for this type of
actuation is always negative if the uncontrolled flow stays laminar. However, we show that a positive net power
balance can be achieved when the uncontrolled flow becomes turbulent but the controlled flow stays laminar.
Starting from this observation, we develop a framework for selection of traveling wave parameters for control of
transition with a positive net power balance. Our model-based approach shows that, relative to the uncontrolled
flow, the velocity fluctuations around the upstream traveling waves at best exhibit similar sensitivity to back-
ground disturbances. In contrast, the properly designed downstream traveling waves can significantly reduce
sensitivity which makes them well-suited for preventing transition. Our theoretical findings are confirmed by di-
rect numerical simulations of the Navier-Stokes (NS) equations which show that a positive net efficiency as large
as 25% relative to the uncontrolled turbulent flow can be achieved. This (i) elucidates the predictive power of the

  

Source: Akhmedov, Azer - Department of Mathematics, University of California at Santa Barbara

 

Collections: Mathematics