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首页> 外文期刊>Experiments in Fluids: Experimental Methods and Their Applications to Fluid Flow >Characteristics of fluorescein dye and temperature fluctuations in a turbulent near-wake
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Characteristics of fluorescein dye and temperature fluctuations in a turbulent near-wake

机译：湍流近尾时荧光素染料的特性和温度波动

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The Laser Induced Fluorescence (LIF) technique was used to determine a few characteristics of a high Schmidt number (Sc) passive scalar (fluorescein) in the near-wake of a circular cylinder. The mean and rms concentration indicate that increasing the Reynolds number (Re) improves the large-scale mixing and accelerates the homogenisation of the scalar. As Re increases, the intensity of segregation decreases because of turbulent diffusion but the scale of segregation increases due to dispersion. Comparison between concentration and temperature rms profiles indicates that molecular diffusion has a much smaller effect on the decay of the scalar variance than the Reynolds number. The ratio of mean-squared values of lateral and streamwise spatial derivatives of the scalar fluctuation deviates from isotropy, the departure increasing with Re. This reflects more the effect of dispersion by the turbulent velocity field rather than any molecular diffusion effect. At a given Re, the ratio decreases as the distance from the cylinder increases. This trend is more accentuated near the edge of the wake than at the centreline. [References: 23]
机译：激光诱导荧光（LIF）技术用于确定圆柱体近尾时高Schmidt数（Sc）被动标量（荧光素）的一些特征。平均值和均方根浓度表明，增加雷诺数（Re）可以改善大规模混合并加速标量的均质化。随着Re的增加，由于湍流扩散，偏析强度降低，但由于扩散，偏析的规模增大。浓度和温度均方根曲线之间的比较表明，分子扩散对标量方差衰减的影响比雷诺数小得多。标量波动的横向和流向空间导数的均方值之比偏离各向同性，偏离随Re增加。这更多地反映了湍流速度场的分散作用，而不是任何分子扩散作用。在给定的Re下，该比率随着与圆柱体的距离增加而减小。这种趋势在尾流边缘附近比在中心线处更加突出。 [参考：23]

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