Stochastic geometric properties of scalar interfaces in turbulent jets

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Abstract
Experiments were conducted in which the behavior of scalar interfaces in turbulent jets was examined, using laser‐induced fluorescence (LIF) techniques. The experiments were carried out in a high Schmidt number fluid (water), on the jet centerline, over a jet Reynolds number range of 1000≤Re≤24 000. Both two‐dimensional scalar data, c(r,t) at fixed x/d, and one‐dimensional scalar data, c(t) at fixed x/d and r/x, were analyzed using standard one‐ and two‐dimensional fractal box‐counting algorithms. Careful treatment was given to the handling of noise. Both long and short records as well as off‐centerline measurements were also investigated. The important effect of threshold upon the results is discussed. No evidence was found of a constant (power‐law) fractal dimension over the range of Reynolds numbers studied. On the other hand, the results are consistent with the computed behavior of a simple stochastic model of interface geometry.