Turbulence and drag control in jet and wake flows |
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Authors: | S Rajagopalan R A Antonia |
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Affiliation: | (1) School of Engineering, University of Newcastle, Newcastle, Australia |
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Abstract: | Structures of plane and circular jets were modified by using active, passive and an active-passive (hybrid) combination to
investigate the phenomenon of turbulence control using hot-wire anemometry. Active control was achieved by exciting the flow
by using either an acoustic speaker or vibrating piezoceramic elements, whereas passive control was achieved by placing a
slender object such as a thin wire or a ring, a mesh or a honeycomb section downstream of the nozzle exit plane. Turbulence
enhancement and suppression in plane-and circular-jet mixing layers could be achieved by employing active techniques, whereas
passive techniques essentially yielded turbulence reduction. For a circular cylinder, a significant reduction in drag was
obtained by placing a cylinder of small diameter upstream of the main cylinder. The total drag of the two cylinders was smaller
than that of a single cylinder alone. Hot-wire measurements indicate significant changes to the downstream flow structure
associated with the observed drag reduction. Our investigations indicate that different types of modification and excitation
can yield different but useful outcomes. |
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Keywords: | Jets and wakes organised structures turbulence control active and passive techniques bluff body drag |
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