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首页> 外文期刊>Journal of Heat Transfer >Self-Preserving Mixing Properties of Steady Round Buoyant Turbulent Plumes in Uniform Cross-flows
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Self-Preserving Mixing Properties of Steady Round Buoyant Turbulent Plumes in Uniform Cross-flows

机译：均匀横流中稳定圆形浮力紊流羽流的自保持混合特性

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The self-preserving mixing properties of steady round buoyant turbulent plumes in uniform cross-flows were investigated experimentally. The experiments involved salt water sources injected into fresh water cross-flows within the windowed test section of a water channel. Mean and fluctuating concentrations of source fluid were measured over cross sections of the flow using planar-laser-induced fluorescence which involved seeding the source fluid with Rhoda-mine 6G dye and adding small concentrations of ethanol to the cross-flowing fluid in order to match the refractive indices of the source flow and the cross-flow. The self-preserving penetration properties of the flow were correlated successfully based on the scaling analysis of Diez, Bernal, and Faeth (2003, ASME J. Heat Transfer, 125, pp. 1046-1057) whereas the self-preserving structure properties of the flow were correlated successfully based on the scaling analysis of Fischer et al. (1979, Mixing in Inland and Coastal Waters, Academic Press, New York, pp. 315-389); both approaches involved assumptions of no-slip convection in the cross stream (horizontal) direction (parallel to the cross-flow) and a self-preserving line thermal having a conserved source specific buoyancy flux per unit length that moves in the stream-wise (vertical) direction (parallel to the direction of both the initial source flow and the gravity vector). The resulting self-preserving structure consisted of two counter-rotating vortices having their axes nearly aligned with the cross-flow direction that move away from the source in the stream-wise (vertical) direction due to the action of buoyancy. Present measurements extended up to 202 and 620 source diameters from the source in the stream-wise and cross stream directions, respectively. The onset of self-preserving behavior required that the axes of the counter-rotating vortex system be nearly aligned with the cross-flow direction. This alignment, in turn, was a strong function of the source/cross-flow velocity ratio, u{sub}o/v{sub}∞. The net result was that the onset of self-preserving behavior was observed at streamwise distances of 10-20 source diameters from the source for u{sub}o/v{sub}∞=4 (the smallest value of u{sub}o/v{sub}∞ considered), increasing to stream-wise distances of 160-170 source diameters from the source for u{sub}o/v{sub}∞=100 (the largest value of u{sub}o/v{sub}∞ considered). Finally, the counter-rotating vortex system was responsible for substantial increases in the rate of mixing of the source fluid with the ambient fluid compared to axisymmetric round buoyant turbulent plumes in still environments, e.g., transverse dimensions in the presence of the self-preserving counter-rotating vortex system were 2-3 times larger than the transverse dimensions of self-preserving axisymmetric plumes at similar stream-wise distances from the source.
机译：实验研究了稳定的圆形浮力紊流在均匀横流下的自保持混合特性。实验涉及将盐水源注入到水通道开窗测试区内的淡水交叉流中。使用平面激光诱导的荧光测量了流体横截面的平均和波动浓度，该荧光涉及用Rhoda-mine 6G染料播种源流体，并向交叉流动的流体中加入少量乙醇，以匹配源流和交叉流的折射率。根据Diez，Bernal和Faeth（2003年，ASME J.传热，125，第1046-1057页）的比例分析成功地关联了流的自保存渗透特性。根据Fischer等人的规模分析，成功地将流量关联。 （1979年，《内陆和沿海水域的混合》，纽约学术出版社，第315-389页）；两种方法都涉及以下假设：在横流（水平）方向（平行于横流）上无对流，以及在每单位长度上具有保守的源比浮力通量的自保管线热（沿流向移动（ （垂直）方向（平行于初始源流和重力矢量的方向）。所得的自保持结构由两个反向旋转的涡流组成，它们的轴几乎与横流方向对齐，由于浮力的作用，它们沿流向（垂直）方向远离源移动。当前的测量值分别从源沿流向和跨流方向扩展到源直径最大202和620。自保持行为的开始要求反向旋转涡流系统的轴几乎与横流方向对齐。反过来，这种对准是源/横流速度比u {sub} o / v {sub}∞的强大函数。最终结果是，对于u {sub} o / v {sub}∞= 4（u {sub} o的最小值），在距源的直径为10-20的源直径的流向距离上观察到了自保留行为的开始。 / v {sub}∞），对于u {sub} o / v {sub}∞= 100（u {sub} o / v的最大值），从源到源的流向距离增加至160-170 {sub}∞）。最后，与静态环境下的轴对称圆形浮力湍流羽流相比，反向旋转涡流系统显着提高了源流体与环境流体的混合速率，例如在存在自保持计数器的情况下的横向尺寸旋转涡流系统是自保持轴对称羽流的横向尺寸的2-3倍，且距源的流向距离相似。

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