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ICHMT DIGITAL LIBRARY ONLINE

ISSN 961-91393-0-5

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Year 2006

• 1Turbulence, Heat and Mass Transfer 5
Proceeding of The International Symposium on Turbulence, Heat and Mass Transfer - Dubrovnik, Croatia, September 25-29, 2006

806 pages

Volume price - $246.00

Effects of Periodic Excitation on the Characteristics of a Turbulent Boundary Layer

J. Ortmanns
Institute of Fluid Mechanics, Technical University Braunschweig, Bienroder Weg 3, 38106 Braunschweig, Germany

M. Bitter
Institute of Fluid Mechanics, Technical University Braunschweig, Bienroder Weg 3, 38106 Braunschweig, Germany

C. J. Kahler
Institute of Fluid Mechanics, Technical University Braunschweig, Bienroder Weg 3, 38106 Braunschweig, Germany

ABSTRACT

This contribution summarizes the investigations of two flat plate experiments in a water tunnel which deal with the dynamic response and the characteristics of a turbulent boundary layer in interaction with coherent structures induced by dynamic vortex generator jets. The results show that the characteristics of the turbulent fluctuations are nearly unaffected by the flow control process. This allows a separation of scales for physical interpretation and numerical simulation. Secondly, the initial blowing produces an increasing mixing force compared to the steady blowing case, which is even present at high duty-cycles. It is independent of the duty-cycle but varies with the blowing ratio. By considering decay and rebirth of the dynamic vortex structures a new estimation of an optimal frequency for this flow control strategy can be established.