水质对梢涡空化初生的影响及其模化研究

Tip vortex cavitation is an important type of cavitation. It looks like a line-shape cavity, radiating strong harmful noise. There is an urgent need to accurately predict its inception, not only in the military field but also in the civil field. The occurrence of tip vortex cavitation is very sensitive to the condition of water quality. However, it’s not easy to carry out a quantitative study since the nuclei involved in water are small in size and complex in distribution. This project is an attempt to study in nucleus-scale, to investigate the migration and growth of nuclei in the ideal and tip vortex flows. Following the measurements of water quality, the experiments of cavitation inception and the simulations of motion of nuclei will be performed. The features of evolution of nuclei in the tip vortex flow will be analyzed in order to reveal the occurrence mechanism of tip vortex cavitation. The core information in the nuclei distribution will be presented so that the tensile strength of water can be expressed quantitatively. The tensile strength will be used to improve the existing cavitation theories and cavitation models. The research work in this project will be helpful to intensify the knowledge of occurrence mechanism of cavitation inception, and also benefit to the improvements of the quantitative study and prediction of tip vortex cavitation.

梢涡空化是空化中的重要类型，呈细长的线状空化形态，具有强烈的噪声危害，军事领域和民用领域都对其精确预报具有迫切需要。梢涡空化的发生对水质条件很敏感，但由于各类水体中气核尺度很小、分布不一，不利于对其进行定量化研究。本项目拟以气核动力学行为为突破口，对气核在理想涡流、梢涡流场中的迁移和生长过程进行研究。以实测水质条件为依据，开展空化初生实验和气核运动模拟。分析气核群在梢涡流场中的演化过程，揭示梢涡空化发生的物理机理。筛选水质条件中的核心信息，定量描述水体抗拉强度，改进当前的空化理论和空化模型。本项目的研究，将有助于提升空化发生机理的认识，提高梢涡空化的定量化研究水平和预报能力。

梢涡空化是实船螺旋桨上最早发生的空化类型，会导致强烈的噪声、振动以及剥蚀等后果，因此工程领域中对于其准确的预报有着迫切的需求。水质对梢涡空化初生具有很大影响，目前还缺乏合适的定量评估方法，需要发展适用于梢涡空化预报的理论和模型。本项目以叶梢涡流场为背景，采用理论分析和数值模拟方法，研究了气核在梢涡流场中的迁移、生长过程。采用欧拉-拉格朗日模型，数值模拟得到了气核在涡流中的运动过程，解释了具有一定气核谱分布的水质条件如何影响梢涡空化初生。同时对气核运动过程进行了理论分析，获得了气核捕捉时间的解析表达。通过解析解，可以快速的筛选出临界气核，以临界气核的张力作为液体的抗拉强度，定量的表征了水质对梢涡空化初生的影响。新模型将有利于提高梢涡空化初生预报的精度，能够为船舶螺旋桨的设计和空化预报服务。