声场作用下复杂流体液滴的形态振荡、失稳及凝并研究

声场与流体液滴的相互作用在微流体、化工等诸多领域都有十分重要的应用。然而，声场如何影响复杂流体液滴的动态行为仍不清楚，严重限制了复杂液滴的应用及其动力学理论的进一步发展。本项目以超声悬浮、高速摄影和PIV技术为主要研究手段，通过控制声场实现复杂液滴的悬浮，主动激励其产生振荡、毛细波、雾化等动态行为，利用高速摄影对其进行拍摄。研究声悬浮条件下液滴的振荡动力学规律，探索液滴表面毛细波的激发条件及其色散关系，研究液滴在声场中的失稳现象以及多个液滴的凝并行为。项目所采用的声悬浮技术提供了液滴非接触操控的实验条件，排除了界面效应对液滴动态行为的干扰，结合声场计算、液滴内部和外部流场观测以及流变性质研究，阐明“液滴动态行为-声场-液滴流变性质”之间的内在关联，揭示复杂流体液滴与超声场的相互耦合机制。项目有望建立基于声悬浮技术的液滴流变性质研究的新方法，为开发新型流变仪及液滴操控平台奠定理论基础。

The interaction between sound field and liquid droplets plays an important role in many fields such as microfluidics and chemical engineering. Until now, however, it is not clear how the sound field affects the dynamic behavior of complex fluid droplets. This seriously limits the applications of such droplets and the understanding of its dynamics. This proposed project uses ultrasonic levitation, high-speed photography and PIV technology as the main experimental methods. By controlling the sound field to realize stable levitation of complex droplet, and actively stimulate it to exhibit oscillation, capillary wave, atomization and other dynamic behaviors, which will be monitored by using of high-speed photography. This project studies the sectorial oscillation dynamics of complex fluid droplets under acoustic levitation, explores the excitation conditions of capillary waves on the droplet surface and their dispersion relations, and studies the instability of droplets in the sound field and the coalsecence behavior of multiple droplets. The acoustic levitation provides a non-contact manipulation of droplets, thus eliminating the effect of interface on the droplet dynamic behaviors. By further numerical calculation of sound field, analysis of the internal flows and external flows of the levitated droplets, and the study of the liquid rheology, the relation between droplet dynamic behavior, sound field and droplet rheological properties can be clarified, of the inner link, and the mutual coupling mechanism between complex fluid droplets and sound field can be elucidated. After conducting the project, it is expected to develop a new method to study the rheological properties of complex fluids based on acoustic levitation, and establish a theoretical foundation for the development of new rheometer as well as novel droplet manipulation platform.