Measurements of rising velocity of a small bubble in a stagnant fluid in one- and two-component systems
Measurements of rising velocity of a small bubble in a stagnant fluid in one- and two-component systems
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DOI：
10.1016/j.expthermflusci.2006.06.006
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发表时间：
2007-05-01
影响因子：
3.2
通讯作者：
Tomiyama, Akio
中科院分区：
文献类型：
--
作者：
Celata, Gian Piero;D'Annibale, Francesco;Tomiyama, Akio
尽管其表面上很简单，但精确确定静止流体中气泡的形状和速度的问题还远未得到解决。文献中的大多数模型都利用三个无量纲参数来关联数据，但是根据实验证据，支配该现象的自变量的数量正在不断增加。本文的目的是评估文献中相对简单和一般的相关性在广泛的实验数据集上的气泡终端上升速度和纵横比的准确度，这些实验数据是通过使用不同的注射装置（喷嘴和孔口）将气泡注射到两种不同的流体（水和 FC-72，3M 的氟惰性商标）中获得的。考虑了双组分（不同液体中的气体）和单组分（液体中的蒸气）系统。为此，建造了一个简单的实验装置，并通过分析高速相机拍摄的图像来确定气泡的速度和形状。将测量的单个气泡的形状（纵横比）和上升速度与可用的相关性进行比较。比较表明，长径比与 Tadaki 数有很好的相关性，或者在较小程度上与 Weber 数相关。在测试的相关性中，Taylor & Acrivos 和 Vakhrushev & Efremov 提出的相关性在观测范围内给出了更好的结果。关于终端上升速度，选择了几种相关性，它们的预测在整个观测范围内通常表现出高达 50% 的误差，Tomiyama 等人的最新模型给出了最好的精度。 (c) 2006 Elsevier Inc. 保留所有权利。
Despite its apparent simplicity, the problem of accurate determination of the shape and velocity of a bubble in a still fluid is far from being solved. Most of the models available in the literature make use of three dimensionless parameters to correlate the data, but, according to experimental evidence, the number of independent variables ruling the phenomenon is continuously increasing. The purpose of the present paper is to assess the degree of accuracy of relatively simple and general correlations available in literature for the terminal rising velocity and aspect ratio of a bubble over a wide experimental data set, obtained by injecting bubbles in two different fluids (water and FC-72, a fluoroinert trade mark of 3M) with different injection devices (nozzles and orifices). Both two-components (gas in a different liquid) and one-component (vapor in its liquid) systems were considered. To this aim, a simple experimental apparatus was built and the bubble velocity and shape were determined by analyzing the images taken with a high-speed camera. Measured shapes (aspect ratio) and rising velocities of single bubbles were compared with available correlations. The comparison showed that the aspect ratio was well correlated by the Tadaki number or, to a little lesser extent, by the Weber number. Among the correlations tested, the ones proposed by Taylor & Acrivos and Vakhrushev & Efremov gave the better results in the observed range. Concerning the terminal rising velocity, several correlations were selected and their predictions exhibited generally an error up to 50% throughout the observed range, the best accuracy being given by the recent model of Tomiyama et al. (c) 2006 Elsevier Inc. All rights reserved.