• Journal of Mechanical Science and Technology
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• 제15권4호
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• pp.522-530
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• 2001

An experimental study of compressible jet flows has been undertaken in a small transonic wind tunnel. The aim of this investigation was to realize a jet simulator in the framework of wing/nacelle integration research and to characterize the jet flow behavior. First, free jet configuration, and subsequently jet flow in co-flowing air stream configuration were analyzed. Flow conditions were those encountered in a typical flight condition of a generic transport aircraft, i.e. fully expanded sonic jet flows interacting with a compressible external flowfield. Conventional experimental techniques were used to investigate the jet flows-Schlieren visualization and two-component Laser Doppler Velocimetry (LDV). The mean and fluctuating properties were measured along the jet centerline and in the symmetric plane at various downstream locations. The results of two configurations show remarkable differences in the mean and fluctuating components and agree well with the trend observed by other investigators. Moreover, these experiments enrich the database for such flow conditions and verify the feasibility of its application in future aerodynamic research of wing/nacelle interactions.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2002년도 학술대회지
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• pp.221-224
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• 2002

A technique of mixing enhancement in an underexpanded sonic round jet is studied with fully expanded jet Mach number 1.5. Tonal sound, jet screech can be produced at some underexpansion pressure ratio in a sonic jet. Since the jet screech excites the initial Jet shear layer to change the flow, a reflector which focuses the jet screech near the nozzle lip is designed. The reflector has an elliptic shape of which two foci are located near the nozzle lip and the jet screech source region. Jet screech tone near the nozzle lip increases with the elliptic reflector and spreading of the jet largely increases. It is concluded that mixing enhancement of the jet with the elliptic reflector is attributed to large scale structures which are initially excited by the increased jet screech.