【摘要】 利用高速摄影技术研究了压扁液滴自由落体过程中的形态演变.实验中利用表面活性剂十二烷基硫酸钠(SDS)对液滴性质进行调控.实验发现,液滴的形态演变显著依赖于SDS浓度.有趣的是,SDS浓度为0.8 cmc时,液滴可较长时间保持压扁形态而不回复成球形.经受力分析,界面的Gibbs弹性不足以完全抵消Laplace压差所产生回复力.声场作用下产生的宏观表面浓度梯度导致强烈的Marangoni效应,赋予界面以额外弹性,从而与液滴回复力相抗衡.更多还原

【Abstract】 We have investigated the shape evolution of pre-compressed oblate droplets during free fall by using a high speed camera. In the experiments, the properties of the droplets were tuned by sodium dodecylsulfate(SDS). It has been found, the shape evolution strongly depends on the concentration of SDS. Interestingly, the droplets with concentration of 0.8 cmc can maintain its compressed state for long time(>50 ms) without recovering to spherical shape. While the droplets of other concentrations exhibit obvious recovery and oscillation. The Gibbs elasticity of the droplet surface is not sufficient to balance the Laplace pressure which drives the droplets recover. It is deduced that the Marangoni effect caused by the SDS concentration gradient which is induced by the acoustic field plays an important role. This effect results in larger additional surface elasticity, accompanying the Gibbs one, to the droplet which balances its recover force.更多还原