Study on a quantitative measurement using laser induced fluorescence and a model of bubble motion in linear shear flows

测量了单个气泡在甘油-水溶液线性剪切流动中的运动轨迹，以评估作用在气泡上的横向升力。实验是在以下条件下进行的：-5.5^gt；log M</sup>-2.8，1.39^t^t</sup>^5.8^gt；^5.8</sup>5.74⁰且^gt；</sup><，其中M为Morton数，Eo为Eotvos数，Dv_L/dy为液体线性剪切流动的速度梯度。利用所有测量的轨迹和气泡运动方程，计算了净横向升力系数C_T。小气泡的温度与气泡的雷诺数有很好的相关性，而大气泡的温度与修正的Eotvos数有很好的相关性，修正的Eotvos数是用变形气泡的最大水平尺寸作为特征长度来定义的。由此得到的C_T相关性由下列方程给出。The Critic…用5~6 mm的C_T关联式估算了气液两相气泡上升流径向空泡分布由壁峰向芯峰转变的较大泡径，与已有的径向空泡分布实验数据吻合较好。利用净横向升力和壁力之间的简单力平衡，可以预测垂直管内气泡上升流中气泡最可能的径向位置。为了测量单个气泡后面的详细尾迹结构，开发并评估了一种基于激光诱导荧光的非侵入性测量技术。实验证明，该方法可以同时测量相分布函数和液体速度，具有较高的空间和时间分辨率。测量结果表明，尾迹结构主要由变形气泡的最大水平尺寸决定，而不是由气泡的当量直径决定，液体速度梯度是气泡尾迹变形的主要原因。较少

Trajectories of single air bubbles in linear shear flows of glycerol-water solution were measured to evaluate transverse lift force acting on a bubble. Experiments were conducted under the conditions of -5.5 <less than or equal> log M <less than or equal> -2.8, 1.39 <less than or equal> Eo <less than or equal> 5.74 and 0 <less than or equal> "*"dV_L/dy"*" <less than or equal> 8.3s^<-1>, where M is the Morton number, Eo the Eotvos number and dV_L/dy the velocity gradient of the linear shear flow of liquid. Making use of all the measured trajectories and an equation of bubble motion, a net transverse lift coefficient C_T was evaluated. The C_T for small bubbles was found to be well correlated with the bubble Reynolds number, whereas C_T for large bubbles was well correlated with a modified Eotvos number, which was defined by using the maximum horizontal dimension of a deformed bubble as a characteristics length. The resulting C_T correlation is given by the following equations.The critic … More al bubble diameter causing the radial void profile transition from wall peaking to core peaking in an air-water bubbly upflow was evaluated with the C_T correlation as 5 to 6 mm, which is in good agreement with available experimental data on radial void profiles. It is possible to predict the most probable radial position of a bubble in a bubbly upflow in a vertical pipe using a simple force balance between the net transverse lift force and wall force.To measure detailed wake structure behind single bubble, a non-intrusive measurement technique using laser induced fluorescence was developed and evaluated. It was confirmed that the present method can measure the phase distribution function and the liquid velocity simultaneously with high spatial and time resolutions. The measured results indicates that the wake structure was dominated by the maximum horizontal dimension of a deformed bubble rather than the equivalent diameter of the bubble, and the liquid velocity gradient induced the deformation of the bubble wake. Less