Master Degree / Yüksek Lisans Tezleri
Permanent URI for this collectionhttps://hdl.handle.net/11147/3008
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Master Thesis Experimental Investigation of Heat and Fluid Flow in an Actuated Impinging Jet Flow(Izmir Institute of Technology, 2009) Bilgin, Necati; Özkol, Ünver; Özkol, Ünver; 03.10. Department of Mechanical Engineering; 03. Faculty of Engineering; 01. Izmir Institute of TechnologyThe objective of this work is to how the surface heat transfer and flow characteristics can be affected by jet flow by excitation of which changes the turbulence characteristics of the flow. Main body of this work is experimental analysis; nevertheless some simple numerical analysis is also presented in order to make some comparisons. The hot-wire measurements and flow visualizations are performed. As a flow actuator a loudspeaker is used once the piezo-electric benders were found to be unsuccessful. Acoustic (pressure) wave generated by the loudspeaker travels along the flow system and reaches the jet nozzle where it generates an oscillating component on the mean nozzle velocity. Parameters used on this study are shortly Re.10000, dimensionless jet to plate distance is equal to 6, as a non-dimensional excitation frequency Strouhal number is changed in the range of 0.St.1, and as for the excitation amplitude, voltages sent to the 20X amplifier are 0.5V, 1.0V and 1.5V.Master Thesis Enhancement of Jet Shear Layer Mixing and Surface Heat Transfer by Means of Acoustic Disturbances(Izmir Institute of Technology, 2010) Kor, Orçun; Özkol, Ünver; Özkol, Ünver; 03.10. Department of Mechanical Engineering; 03. Faculty of Engineering; 01. Izmir Institute of TechnologyThe objective of this thesis is to investigate how the surface heat transfer of an impinging jet flow can be increased by acoustic actuation of which changes the turbulence characteristics of the flow. This work is built upon experimental studies which includes flow visualization experiments and surface heat transfer measurements. A loudspeaker system which is controlled by means of a function generator is used for the purpose of actuating impinging jet flow. Acoustic waves in different waveforms, frequencies and amplitudes which are generated by the loudspeaker reaches the jet nozzle, resulting in the formation of an oscillating component on the mean nozzle velocity since the actuation itself is in the form of a periodic fluctuation. It is this oscillating component that actuates the shear layer of the jet flow. Reynolds number is kept at 10.000 for all experimental cases. Influence of nozzle geometry is investigated by using sudden and smooth contracting (with a curvature of 5 degree polynomial) nozzles. Dimensionless nozzle-to-plate spacing is adjusted between 2, 4 and 6. Strouhal number, which is the non-dimensional form of actuation frequency is changed between0 < St < 1. The amplifier, which is used for generating sine and square waves, is set for 1.5 and 2 Volts amplitudes.