中文摘要：

采用激光影像技术,对羧甲基纤维素（CMC）水溶液中气泡生成过程中的形状演变进行了实时观测。利用激光多普勒测速仪（LDV）对气泡生成和上升过程中周围液相流场进行了测定,得到了气泡周围的液相时均速度分布以及在测试截面上的速度等值图。结果表明,在气泡生成初期,由于表面张力占主导作用,气泡呈球形增长;随后在浮力和和剪切稀化共同作用下,气泡逐渐被拉伸呈泪滴状;液相轴向时均速度对喷嘴中心垂线呈高斯分布,径向时均速度随着与喷嘴中心垂线距离的增加,先增加后减小。在实验范围内,轴向时均速度随高度的增加先减小后增大,其等值图则逐渐发散;而径向时均速度随高度的增加逐步减小,其等值图中极大值缓慢向两边偏移直到消失,整体沿喷嘴中心垂线呈蝴蝶＂前翅膀＂状。

英文摘要：

The shape evolution of the bubble formed in carboxymethylcellulose（CMC） aqueous solution was observed in real time utilizing laser image technique.The flow fields of liquid surrounding the growing and rising bubble were measured by laser Doppler velocimetry（LDV）,and the distribution of mean velocity of liquid around the rising bubble and velocity contour curves in test section were obtained.The results show that the bubble grows into spherical shape due to the predominant role of surface tension in initial period,and then is stretched gradually as tear-drop shape due to the common effect of buoyancy and shear-thinning of fluid.The axial mean velocity of liquid phase takes on Gaussian distribution with the vertical symmetry through the orifice centre,whereas the radial mean velocity increases firstly and deceases subsequently with the increase of the distance from the measured point to the vertical symmetry line.Within the experimental range,the axial mean velocity decreases in initial stage and then increases with the rise of height,accompanied with the gradual divergence of velocity contour curves.However,the radial mean velocity decreases gradually with the rise of height,and the maximum value of velocity contour curves deviates towards two sides until disappearance,taking on the shape of butterfly′s ＂front wing＂ with the vertical symmetry.