Abstract
Techniques have been developed to measure the concentration of nozzle gas quantitatively in transitional and turbulent flow regimes at high framing rates in two dimensions. Elastically scattered light from a seeded jet, illuminated by a sheet of laser light, was recorded in three ways. The first involved the use of a rotating mirror to sequentially place images onto different portions of a relatively slow vidicon-based imaging system to achieve a high effective framing rate (2–10 kHz) for up to four frames. The second used a portion of a monolithic 128×128 photodiode array connected directly to a high-speed analog to digital converter to achieve a framing rate of 1.136 kHz. The third used a fast video camera and recorder (6 kHz) to store images on magnetic tape in analog form, which were later digitized upon playback. A comparison of these techniques is presented along with a discussion of factors important in the use of high-speed digital imaging systems. It is shown that the temporal development of large-scale structures can be digitally recorded in two dimensions, with the advantage of being both quantitative and visually interpretable.
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Winter, M., Lam, J.K. & Long, M.B. Techniques for high-speed digital imaging of gas concentrations in turbulent flows. Experiments in Fluids 5, 177–183 (1987). https://doi.org/10.1007/BF00298458
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DOI: https://doi.org/10.1007/BF00298458