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首页> 外文期刊>Journal of Heat Transfer >Self-Preserving Properties of Unsteady Round Buoyant Turbulent Plumes and Thermals in Still Fluids
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Self-Preserving Properties of Unsteady Round Buoyant Turbulent Plumes and Thermals in Still Fluids

机译：不稳定流体中非定常圆形浮力湍流羽和热的自保持性质

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摘要

The self-preserving properties of round buoyant turbulent starting plumes and starting jets in unstratified environments. The experiments involved dye-containing salt water sources injected vertically downward into still fresh water within a windowed tank. Time-resolved images of the flows were obtained using a CCD camera. Experimental conditions were as follows: source diameters of 3.2 and 6.4 mm, source/ambient density ratios of 1.070 and 1.150, source Reynolds numbers of 4,000-11,000, source Froude numbers of 10-82, volume of source fluid for thermals comprising cylinders having the same cross-sectional areas as the source exit and lengths of 50-382 source diameters, and stream-wise flow penetration lengths up to 110 source diameters and 5.05 Morton length scales from the source. Near-source flow properties varied significantly with source properties but the flows generally became turbulent and then became self-preserving within 5 and 20-30 source diameters from the source, respectively. Within the self-preserving region, both normalized streamwise penetration distances and normalized maximum radial penetration distances as functions of time were in agreement with the scaling relationships for the behavior of self-preserving round buoyant turbulent flows to the following powers: time to the 3/4 power for starting plumes and to the 1/2 power for thermals. Finally, the virtual origins of thermals were independent of source fluid volume for the present test conditions.
机译：在非分层环境中，圆形浮力湍流起始羽流和起始射流的自我保存特性。实验涉及将含染料的咸水源垂直向下注入到开窗的水箱内的淡水中。使用CCD摄像机获得了时间分辨的流动图像。实验条件如下：源直径为3.2和6.4 mm，源/环境密度比为1.070和1.150，源雷诺数为4,000-11,000，源弗洛德数为10-82，用于热学的源流体的体积，包括与源出口相同的横截面面积和50-382源直径的长度，以及沿流向流动的渗透长度，最高为110源直径，源上的莫顿长度为5.05。近源流的性质随源的性质而变化很大，但流通常变得湍流，然后分别在距源5到20到30的源直径范围内变得自保存。在自保持区域内，归一化的水流穿透距离和归一化的最大径向穿透距离作为时间的函数均与自保持圆形浮力湍流行为具有以下幂次的比例关系一致：时间为3 / 4功率用于启动羽流，而1/2功率用于散热。最后，在当前测试条件下，热的虚拟起源与源流体体积无关。

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