Abstract

A laser image measurement system has been established to study the problem of dynamic bubble formation from a submerged orifice in two kinds of high-viscous fluids, namely Newtonian glycerol aqueous solution and non-Newtonian carboxymethylcellulose (CMC) aqueous solutions. The bubble generation process was measured accurately by means of He-Ne laser as light source using the beam expanding and light amplification technology. The whole formation process, including bubble expansion, stretching and detachment three stages, and the dynamic characteristics of each stage, were investigated experimentally by analyzing comparatively the evolution of the instantaneous shape, volume, surface area, and deformation rate in both fluids. The influences of solution mass concentration, gas chamber volume and orifice diameter on bubble detached volume were discussed respectively, and the results reveals that bubble begins to grow spherically due to the predominant role of surface tension, and then is elongated gradually owing to the increasing buoyancy force. Compared with Newtonian fluid, bubble formed in non-Newtonian fluid presents a slim shape as a result of the shear-thinning effect of CMC solution. Bubble detachment volume in both kinds of fluids increases with solution mass concentration and gas chamber volume, but declines with orifice inner diameter, respectively.

摘要

建立了激光图像测量系统，研究了牛顿甘油水溶液和非牛顿羧甲基纤维素（CMC）两种高粘度流体中浸没孔口动态气泡形成的问题。以He-Ne激光器为光源，采用扩束光放大技术，对气泡产生过程进行了精确测量。通过对比分析两种流体的瞬时形状、体积、表面积和变形速率的演变，实验研究了气泡膨胀、拉伸和脱离三个阶段的整个形成过程以及每个阶段的动力学特性。溶液质量浓度的影响，分别讨论了气室体积和孔口直径对气泡脱离体积的影响，结果表明气泡在表面张力的主导作用下开始呈球形生长，然后由于浮力的增加而逐渐拉长。与牛顿流体相比，由于 CMC 溶液的剪切稀化作用，非牛顿流体中形成的气泡呈现出细长的形状。两种流体中的气泡脱离体积随溶液质量浓度和气室体积的增加而增加，但分别随孔口内径的增加而减小。由于 CMC 溶液的剪切稀化作用，在非牛顿流体中形成的气泡呈细长形状。两种流体中的气泡脱离体积随溶液质量浓度和气室体积的增加而增加，但分别随孔口内径的增加而减小。由于 CMC 溶液的剪切稀化作用，在非牛顿流体中形成的气泡呈细长形状。两种流体中的气泡脱离体积随溶液质量浓度和气室体积的增加而增加，但分别随孔口内径的增加而减小。