界面流变表征的成像方法
Imaging method for interface rheological characterization
摘要：
本文研究了水中油滴从毛细管中释放后的自由阻尼振荡。考虑纯庚烷液滴和稀释的原油液滴（在第二种情况下，界面被两亲性物质，原油的天然组分覆盖）。通过高速摄像机拍摄液滴的阴影图像，并通过图像处理检测液滴轮廓。然后将轴对称液滴形状分解成球谐函数，球谐函数构成由瑞利-兰姆理论预测的本征振荡模式。然后得到每个模式的时间演化。精确地确定了主模态（n=2）的频率和阻尼率，并与理论值进行了比较。对于纯庚烷液滴，频率的理论值与实验吻合良好，而阻尼率被理论显著低估。实验结果清楚地表明，不同的模式耦合。因此，能量从模式n=2转移到n=3，这可能解释了所观察到的阻尼率的增强。的界面粘弹性行为，诱导吸附的两亲性物种的自由振荡的效果进行了检查。在实验条件（小振幅振荡和适度老化）下未观察到显著影响。
英文摘要：
The present work investigates free damped oscillations of an oil drop in water after its release from a capillary tube. Both pure heptane drops and diluted crude oil drops are considered (in the second case the interface is covered by amphiphilic species, natural components of crude oil). Shadowgraph images of the drops are taken by means of a high speed camera and the drop contour is detected by image processing. The axisymmetric drop shape is then decomposed into spherical harmonics, which constitute the eigenmodes of oscillations predicted by the Rayleigh-Lamb theory. Time evolution of each mode is then obtained. The frequency and the damping rate of the principal mode (n=2) are accurately determined and compared with theoretical values for an immobile clean drop oscillating around spherical shape. For pure heptane drops, theoretical value of the frequency agrees well with experiments whereas the damping rate is significantly underestimated by theory. The experimental results clearly show that the different modes are coupled. Energy is thus transfered from mode n=2 to n=3, which probably explains the observed enhancement of the damping rate. The effect of the interface viscoelastic behaviour, induced by adsorbed amphiphilic species on the free oscillations was examined. No significant effect was observed in the experiments conditions (small amplitude oscillations and moderate aging).
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