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Title: Interaction of a synthetic Jet with a thermal turbulent boundary layer.
Author: Mitchell , G.
ISNI:       0000 0001 3411 643X
Awarding Body: Queens University Belfast
Current Institution: Queen's University Belfast
Date of Award: 2008
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An experimental study has been performed to determine the influence of a synthetic jet on a thermal turbulent boundary layer. Measurements were carried out using a slot type synthetic jet operated in a water channel. PlV measurements were used to determine how the synthetic jet influenced the velocity field. Two formation methods of the synthetic jet were observed. At high jet to crossflow velocity ratios, the vortices produced by the jet move away from the wall, whereas at low velocity ratios they remain near the surface. As a result of the jet/crossflow interaction, there is a zone of reversed flow immediately downstream of the orifice accompanied by an increase in the velocity fluctuations. The velocity fluctuations decay with increasing distance downstream of the orifice. The magnitude of the velocity fluctuations decays with increasing distance downstream ofthe orifice. As part of a thermal study, LIF was used for temperature measurements of the fluid. During the expulsion cycle, the thermal boundary layer downstream of the orifice thickens, whereas during the suction cycle, the downstream thermal boundary layer is annihilated as it is entrained into the orifice. Hot-films connected to a constant current anemometer measured the plate temperature. The vortices produced by the synthetic jet sweep cool fluid towards the wall, reducing the surface temperature. Due to the oscillatory nature of the synthetic jet flow, the surface temperature fluctuates at the jet formation frequency. Finally, the synthetic was found to enhance the surface heat transfer. The gain in heat transfer is a result of increased mixing near the wall due to interaction of the synthetic jet with the boundary layer. A more powerful synthetic jet provides greater improvement in the average heat transfer. As the power of the synthetic jet increases, the efficiency ofthe jet at improving heat transfer reduces.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available