Measurement of stress between and around 2 bubbles by the flow birefringence measurement under pressure-oscillating field and its application

在压力振荡场作用下，利用高速偏振相机在气泡附近测量了二维延迟分布。CTAB/NaSal（十六烷基三甲基溴化铵和水杨酸钠的混合物）水溶液用作试验液。由于其符合应力-光学规律，且流变特性与UCM模型相似，因此可以利用二维光学各向异性来评价压力振荡场下小气泡附近的流动应力。测试气泡的体积约为2立方毫米。在一段时间内，结果显示出不同的有趣模式。一是在气泡压缩阶段，由于负尾迹的存在，尖头气泡尾部有较强的延迟（即较大的双折射相位差）。另一种是由于气泡膨胀阶段的拉长流动，仅在气泡表面附近出现弱延迟（即相对较小的双折射相位差）。

2D retardation distributions are measured by the high speed polarization camera near the air bubble under pressure-oscillating field. A CTAB/NaSal (a mixture of cetyl-trimethylammonium bromide and Sodium Salicylate) aqueous solution is used as a test fluid. Since it obeys stress-optic rule and the rheological property is similar to the UCM model, the flow stress in the vicinity of the small air bubble under pressure-oscillating field could be evaluated by the 2D optical anisotropy. Volume of the test bubbles is around 2 cubic mm. The results show alternative interesting patterns clearly over a period. The first one is strong retardation (i.e., larger birefringent phase difference) at the tail of the cusped bubble in the bubble compression phase due to the negative wake. And the other one is a weak retardation (i.e., relatively smaller birefringent phase difference) only near the bubble surface due to the elongational flow in the bubble expansion phase.