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THE INTERACTION OF SYNTHETIC JETS WITH ATTACHED AND SEPARATING TURBULENT BOUNDARY LAYER
[Thesis]. Manchester, UK: The University of Manchester; 2014.
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Abstract
Like virtually every other human activity, air transport has an impact on the environment and similar to all other industries environmental impacts and economic issues are exerting more pressure on aircraft sector to meet the demands and implicated conditions. Secondly in today’s competitive industrial performance index new modern techniques are being introduced to improve the aerodynamics so that the efficiency of the newly designed aircrafts could be enhanced. The active flow control techniques have been proved vital towards achieving more effective air flow on the aircraft wing and that eventually helps to increase the lift coefficient at full scale flight. Synthetic jet actuators have been experimentally proved a promising technique towards achieving flow separation delay on the surface they have been deployed on. For the operation the synthetic jet actuators offer a unique characteristic in that they make use of the ambient work fluid and that deny the need of any extra fluid from outside the system and that helps in two fold. Firstly the need to make additional arrangements for air supply through the complex piping system has been ruled out completely. Secondly in the system the addition of any new weight that usually associates with the introduction of any new technique has been avoided.In this work firstly the dye visualization technique is used to study the interaction of the synthetic jet with both types of boundary layers that is laminar and turbulent. Secondly PIV measurements are performed to quantitatively analyze the evolution of vortical structures in the boundary layer. The aim is to understand the fluid dynamics involved in the interaction of the vortical structures with the neal wall fluid that ultimately re-attach the flow with the surface. Lastly an artificial flow separation is generated on the deflected flat plate surface and the synthetic jet is deployed to observe the separation delay on the surface. Various vortical structures have been generated by operating the actuator at varying parameters and issued into the boundary layer upstream of the separation line. The effectiveness of each type of vortices has been evaluated quantitatively to work out the optimum parameters at which the actuator must be operated to achieve the best control effect at the given free-stream condition.