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.