梢隙涡空化初生的流动控制方法研究

When the static pressure of tip vortex core is lower than the saturated vapor pressure, the water there vaporizes, i.e. tip vortex cavitation occurswith cavitation noise, which deteriorates the stealth of submarines. However, the effect of three dimensional turbulence on the tip clearance vortex cavitation is unclear and the flow control approach of tip vortex cavitation inception is imperfect. A breakthrough intheoretical research on flow control oftip vortex cavitation inception is urgently needed. .The project aiming at the complex flowfields of the tip clearance formed by a vertical wing and an end wall. The experimental and numerical investigations with high spatial and temporal resolutions are conducted to detect the three dimensional turbulence in the narrow area of tip clearance. The instantaneous velocity, pressure and acoustic fields are measured synchronously and analyzed to take on the evolution of three dimensional turbulent structures, in combination with direct numerical simulation results. Based on both experimental and numerical results, the mechanism of the production, development and interaction of turbulent structures in tip clearance flows under complex boundary conditions is to be revealed. And the underline physics of high turbulence kinetic energy and low shear production in tip clearance vortex core is to be figured out. The flow control method to suppress tip clearance vortex cavitation is to be put forward and its control effect is evaluated quantitatively. Reynolds number effect on the flow control method is also discussed. The combination of physical mechanism research and application fundamental research is emphasized and innovative achievement in science is to provide theory and technique to improve the stealth of submarines.

当梢隙涡心区压力低于水的饱和蒸汽压时，涡心水体气化，即发生梢隙涡空化，并伴随着空化噪声，严重影响潜艇声隐身性能。而梢隙三维湍流对梢隙涡空化初生的影响机理尚不明晰，梢隙涡空化初生的抑制手段尚不完备，梢隙涡空化初生的流动控制理论研究亟待取得突破。.本项目以直立翼型与端壁形成的梢隙复杂流动为研究对象，突破梢隙狭小区域三维湍流的非接触光学测量的关键技术和直接数值模拟技术，以及压力场、声场多场耦合的实验测试技术，结合直接数值模拟结果，精细描述梢隙流场中湍流结构的时空演化过程，揭示梢隙复杂边界条件下湍流结构的产生、演化和相互作用机理，挖掘梢隙涡心处高湍动能、低剪切项的形成机制，提出抑制梢隙涡空化初生的流动控制方法，给出流动控制效果的定量评估及雷诺数影响规律，注重物理机理研究和应用基础研究相结合，为提高我国潜艇的声隐身性能提供科学理论与方法。

本项目针对水下航行体泵喷推进器梢隙涡空化，引起推进器辐射噪声激增，进而影响水下航行体声隐身性能的问题，采用实验研究为主、直接数值模拟和大涡模拟为辅的研究手段，开展梢隙涡空化初生的流动控制方法研究，主要在以下方面取得重要进展：.(1)通过梢隙涡空化临界状态空泡形态高速摄影与空化噪声同步测试信号分析，发现梢隙涡空化初生于翼型端面导缘分离涡再附。.(2)在同样来流条件下，增加导缘分离涡核半径，即可减弱导缘分离涡强度、延迟梢隙涡空化初生，故提出翼型表面柔性镀膜（厚度45±5μm）梢隙流动控制方法，适用于梢隙狭小区域且避免引入额外扰动。.(3)柔性镀膜削弱了梢隙导缘分离涡产生的剪切应力（即削弱了梢隙导缘分离涡结构强度），增强了梢隙导缘分离涡涡心区的压力脉动（即破坏了刚性表面梢隙导缘分离涡的低压区），为柔性镀膜延迟梢隙涡空化初生的物理机理。.(4)柔性镀膜延迟梢隙涡空化初生效果定量评估：柔性镀膜使梢隙导缘分离涡在翼型端面的分离长度显著增加1.12至2.33倍，使导缘分离涡区雷诺切应力减小了一半（50.38%）、压力脉动均方根增加了7.7倍，使空化噪声降低26.4dB、泵喷推进器梢隙涡空化初生转速提高4.1~7.9%。.(5)梢隙流场剪切产生项与湍动能分布并不吻合，且梢隙尾缘流场的高湍动能源于梢隙涡的能量输运机制，而非产生于梢隙尾缘流动。.项目成果：完成SCI期刊论文10篇（已见刊8篇）、EI期刊论文1篇（已见刊），受理国家/国防发明专利4项（已授权2项），申请软件著作权1项，完成研究报告5篇，共计21项研究成果；项目研究成果荣获2021创新创业大赛市级决赛二等奖等。.综上所述，本项目研究成果进一步提升了对梢隙涡生成演化及作用机理的认知水平，提出了新颖、有效且具备应用前景的梢隙流动控制方法，厘清流动控制延迟梢隙涡空化初生的物理机理，是湍流与流动控制方法研究成果在水下装备关重件技术瓶颈问题中的典型应用范例。