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

测量了甘油-水溶液线性剪切流中单个气泡的运动轨迹，以确定气泡所受的横向升力。实验在<less than or equal>-5.5logM<less than or equal>-2.8<less than or equal>，1.39Eo <less than or equal>5.74和0<less than or equal>“*“dV_L/dy”*”<less than or equal>8.3s ~<-1>（-1）的条件下进行，其中M为Morton数，Eo为Eotvos数，dV_L/dy为液体线性剪切流的速度梯度。利用所测得的全部轨迹和气泡运动方程，求得了净横向升力系数C_T。发现小气泡的C_T与气泡雷诺数有很好的相关性，而大气泡的C_T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定义的。所得到的C_T相关性由以下等式给出。 ...更多信息 在气-水两相泡状上升流中，气泡直径对气泡径向分布的影响是由壁峰向芯峰转变，C_T关联式为5 ~ 6 mm，与已有的气泡径向分布实验数据吻合较好。利用净横向升力和壁面力之间的简单力平衡，可以预测垂直管道中气泡上升流中气泡的最可能径向位置.为了测量单个气泡后面的详细尾流结构，发展了一种利用激光诱导荧光的非侵入式测量技术.结果表明，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。实验结果表明，气泡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，气泡尾迹的变形是由液体速度梯度引起的。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