表面活性减阻剂注入对绕水翼空化特性的影响及其机理研究

Installing the hydrofoils for the ship can significantly raise the speed of ship. However, cavitation often occurs around the hydrofoil, causing the impact on the hydrofoil, violent vibration and noise. If cavitation around the hydrofoil becomes supercavitation scheme, the resistance can greatly decrease and the occurrence of vibration and noise can also be reduced. It has been proved that decreasing the surface tension of liquid can promote the growth of cavity, making cavitation quickly achieve supercavitation state. Surfactant solution has the characteristics of reducing the surface tension of liquid and turbulent drag-reducing effect. Therefore, an innovative idea using the injection of surfactant solution to control the cavitating flow around the hydrofoil is proposed presently. This project is mainly to study the influencing mechanisms of surfactant additives on cavitating flow. And the research contents include three aspects: (1) Numerically investigating the characteristics of cavitating flow around hydrofoil with the injection of surfactant solution at different inflow velocities, and at different concentrations and velocities of the injecting surfactant solution based on large-eddy simulation; (2) Experimentally investigating the characteristics of cavitating flow around hydrofoil with the injection of surfactant solution; (3) Studying the effects of surfactant additives on the characteristics of cavitating flows around hydrofoil and the corresponding mechanism. This project aims at exploring novel techniques for the control of cavitating flow by means of the injection of surfactant additives. The research achievements are bound to be of great values to the academic, industrial and military applications.

在船舶外安装水翼可以显著提高船舶航行速度,但水翼绕流经常出现空化现象，这将对水翼产生冲击且产生剧烈的振动和噪声。若绕水翼空化达到超空化状态，则航行阻力将大大降低，且减少振动和噪声的发生。研究表明减小液体的表面张力可促进空泡的生长，从而使空化迅速达到超空化。表面活性剂减阻溶液具有减小液体表面张力和湍流减阻效应的特性。因此，本项目提出采用注入表面活性剂减阻溶液控制绕水翼空化流动的创新性思想，主要研究表面活性剂减阻溶液对空化流动的影响机理。具体研究内容包括三个方面：（1）采用大涡数值模拟研究不同来流速度、注入减阻溶液浓度和速度下绕水翼空化流动；（2）采用实验方法研究不同参数下绕水翼空化流动；（3）探究表面活性剂减阻溶液对绕水翼空化流动特性的影响及其机理。本项目旨在探索注入表面活性剂减阻溶液控制空化流动的新技术，研究成果具有重要的学术、民用和军事应用价值。

水翼可以减小舰船的航行阻力，从而提高航速。但在实际使用中经常出现空化现象，尤其是云空化，这将严重损害水翼表面结构，进而产生振动和噪声。为了确保水翼的正常使用，可以采用改变流体物性的方式促进绕水翼云空化快速发展为超空化。研究表明表面活性剂减阻溶液可以通过减小液体的表面张力以达到促进空化流动的目的。所以本项目采用数值模拟和实验研究相结合的方法探究了表面活性剂减阻溶液对绕水翼空化流动特性的影响。首先建立了稳定计算的表面活性剂减阻溶液空化流动大涡数值模拟方法；其次，基于数值模拟和实验数据库，得到了通过狭缝注入表面活性剂减阻溶液下水翼云空化的空泡脱落周期最小，这说明局部改变流体物性可以促进云空化的发展；最后，从涡结构和涡结构与空泡之间相互作用的角度分析了表面活性剂减阻溶液对绕水翼云空化的影响机理，发现表面活性剂减阻溶液主要抑制了小尺度涡结构，从而影响了涡结构的拉伸和膨胀，进而促进了空泡的脱落。本项目的研究成果为未来表面活性剂减阻溶液控制空化流动的应用提供依据，具有重要的学术和应用意义。