Experimental Investigation of Oscillating Subsonic Jets,
NAVAL POSTGRADUATE SCHOOL MONTEREY CA
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The entrainment mechanisms in turbulent jets and methods to increase the entrainment have been a subject of considerable basic and applied interest for many years. Recently, this problem has attracted increased attention because of the need to develop compact, yet highly efficient thrust augmenting ejectors for VSTOL applications. Several new techniques have been introduced or proposed to increase the jet entrainment, e.g. hyper-mixing, swirling, acoustic interactions, and unsteady jet flows. Measurements are described for two-dimensional turbulent free jets which are excited by forced vibration of a small vane located in the jet potential core. Mean velocity measurements using pitot tubes and hot wire or laser-doppler anemometry show significantly increased entrainment rates over the steady turbulent jet. Measurement details and the effect of various parameters, such as nozzle pressure ratio, amplitude and frequency of vane oscillation, are summarized.