壁面几何形状对湍流边界层湍流/非湍流界面特性影响的实验研究

The properties of turbulent/non-turbulent (T/NT) interface in turbulent boundary layers is a hot topic in the research of turbulent flows. The analyzing on T/NT interface, especially at different Reynolds number and over different surface shapes, is the key to understand the entrainment process of turbulent flow, multi-scale structure evolution and to quantify the influenced extension of surface shapes. The present application intends to measure the T/NT interface of turbulent boundary layers over different surface shapes in the Reynolds range of Ret=200-4000 with water tunnel experiment techniques such as hydrogen-bubble visualization, Laser Doppler velocimetry and Large scale time-resolved particle image velocimetry. The main research contents include: ①Analyze the geometrical properties (such as fractal-like properties, characteristic wavelength et al.) and dynamic properties (such as velocity jump, vorticity concentration et al.) of T/NT interface by conditional average, correlation analysis et al. ②Investigate the Reynold effect on geometrical and dynamic properties of T/NT interface to enlarge the Reynolds range of investigation. ③Reveal the effect of surface shapes on turbulent boundary layers by analyzing the distribution of T/NT interface, characteristic wavelength of the interface, and conditional averaged velocity profiles across it. This investigation is expected to find some new phenomena and scaling laws, which is helpful to reveal the mechanism of coherent structure generation, evolution and interaction.

湍流边界层湍流/非湍流界面特性是近年湍流边界层研究的热点问题，对湍流/非湍流界面特性尤其是不同雷诺数以及不同壁面形状下湍流/非湍流界面的差异的研究，是理解湍流扩散和卷吸特性、结构多尺度演化、壁面形状对边界层影响的基础。本申请拟通过水洞氢气泡流动显示、激光多普勒测速以及大视野时间解析的粒子图像测速技术等，对雷诺数范围Ret=200-4000，不同壁面形状下的湍流边界层湍流/非湍流（T/NT）界面进行测量。主要研究内容包括：①通过条件平均、相关分析等方法，研究界面几何特性(如分形特性、特征波长等)以及界面的动力学特性(如速度阶跃、涡量集中等)。②研究雷诺数对界面几何及动力学特性的影响规律及机理。③分析不同壁面形状下T/NT界面统计特性、特征波长、条件平均流场的差异、壁面特性对湍流边界层的影响规律及机理。本研究可望发现一些新的流动现象，为揭示壁面、界面及其相互作用过程中湍流结构的演化提出新的认识

湍流边界层湍流/非湍流（T/NT）界面是理解湍流扩散和卷吸特性、结构多尺度演化、壁面形状对边界层影响的基础。本研究通过高精度、大视野、时间解析的二维和三维粒子图像测量技术，对雷诺数范围Ret=200-4000，9种壁面形状下的边界层T/NT界面进行测量分析。得到的主要成果包括：①提出了高精度、高鲁棒性的T/NT界面识别方法；②研究了不同壁面形状下T/NT界面的几何与动力学特性，发现了壁面摩擦速度是界面动力学特性的合适归一化参数；③研究了雷诺数对界面大尺度波长的影响规律，发现了界面大尺度波长与流向脉动速度外区能谱峰值的一致性；④揭示了对壁湍流具有普适性的壁面形状-大尺度结构-T/NT界面相互作用机理。⑤在项目预期研究内容的基础上，增加了壁湍流转捩阶段T/NT界面特性演化、合成射流T/NT界面特性等方面的研究内容。本研究厘清了T/NT界面特性的雷诺数效应，揭示了壁面、界面及其相互作用过程中湍流结构演化的物理机制，研究成果对壁湍流卷吸、掺混特性的模化与控制提供了重要的物理机制与数据支撑。