Planar laser-induced fluorescence (PLIF) is demonstrated to be a valuable tool for studying the onset of transition to turbulence. For this study, we have used PLIF of nitric oxide (NO) to image underexpanded axisymmetric free jets issuing into a low-pressure chamber through a smooth converging nozzle with a sonic orifice. Flows were studied over a range of Reynolds numbers and nozzle-exit-to-ambient pressure ratios with the aim of empirically determining criteria governing the onset of turbulence. We have developed an image processing technique, involving calculation of the standard deviation of the intensity in PLIF images, in order to aid in the identification of turbulence. We have used the resulting images to identify laminar, transitional and turbulent flow regimes. Jet scaling parameters were used to define a rescaled Reynolds number that incorporates the influence of a varying pressure ratio. An empirical correlation was found between transition length and this rescaled Reynolds number for highly underexpanded jets.


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    Title :

    Fluorescence Imaging Study of Transition in Underexpanded Free Jets


    Contributors:
    Wilkes, J.A. (author) / Danehy, P.M. (author) / Nowak, R.J. (author)


    Publication date :

    2005-01-01


    Size :

    7728343 byte




    Type of media :

    Conference paper


    Type of material :

    Electronic Resource


    Language :

    English



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    Wilkes, J. / Danehy, P. M. / Nowak, R. J. et al. | British Library Conference Proceedings | 2005


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    Wilkes Inman, J. / Danehy, P. / Nowak, R. et al. | British Library Conference Proceedings | 2008


    Fluorescence Imaging Study of Impinging Underexpanded Jets

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    Fluorescence Imaging of Underexpanded Jets and Comparison with CFD

    Wilkes, Jennifer / Glass, Christopher / Danehy, Paul et al. | AIAA | 2006


    Pressure, Temperature and Velocity Measurements in Underexpanded Free Jets using Laser-Induced Fluorescence Imaging

    Naik, Sameer V. / Kulatilaka, Waruna D. / Venkatesan, Krishna K. et al. | AIAA | 2009