基于高频响TR-PIV流场测量和快响应PSP压力场测量的振荡射流流动控制技术的实验研究

Sweeping jet (or fluidic oscillator) provides a novel and promising method for active flow separation control. However, the nature of the self-excited oscillating flow fields still remains unveiled, which is the first step to effectively control flow separation. This research project focuses on two different types of sweeping-jet actuators. i.e. continuous one and scattered one. A series of fundamental experimental investigations on mechanism of the actuators and their control effect on flow separation will be conducted by applying three state-of-the-art fluid mechanics diagnosis instrumentations, i.e., High-Repetition Time-Resolved Particle Image Velocimetry (TR-PIV), Fast Pressure-Sensitive Paint (PSP) and a microphone array. Firstly, the mechanism of the two actuators will be studied in still air chamber. The instantaneous oscillating flow field (measured by TR-PIV) and the dynamic pressure field on the wall inside the actuators (measured by fast PSP) will be measured together with the pressure signal from scattered points on the wall inside the actuators (measured by microphone array). As such to obtain velocity and pressure fields with high resolution in space and time as well as the phase of the oscillating flow. In order to extract the key flow structures from large amount of experimental data, advanced data mining methods, i.e., Proper Orthogonal Decomposition (POD) and Dynamic Mode Decomposition (DMD), will be employed to find the low modes of the unsteady flow fields, and the Q and λci criterion will be used to identify the key vortices. The impact of the different design of the two actuators on the characteristics of the sweeping jets will be studied. Secondly, in a low-speed wind tunnel, the two kinds of actuators will be applied on a NACA0015 airfoil. Using the aforementioned three measurement methodologies and post-processing methods, the interaction between the sweeping jets and the separate flow will be studied, and the flow control effect will be compared. This research project will provide valuable knowledge for effectively application of sweeping jet in flow control.

作为一种较新型的主动控制技术，振荡射流具有在流动控制领域应用的广阔前景。本项目集成高频响粒子图像测速（TR-PIV）流场测量技术、快响应压敏漆（PSP）动态压力场测量技术以及基于传声器阵列的脉动压力测量技术，针对连续型和离散型射流振荡器，对其自激振荡工作机制和流动分离控制机理开展基础实验研究。针对振荡器自激振荡流场，综合采用上述三种先进测量方法，捕捉振荡相位，测得具有高时空分辨率的流场和内壁压力场；采用先进的本征正交模态分解（POD）和动态模式分解（DMD）算法，捕捉大尺度流动结构；采用Q值和λci值算法准确识别旋涡结构；揭示振荡器不同几何结构对其自激振荡流场特性的影响。在流动分离控制实验中，应用NACA0015翼型；使用以上测量和分析方法，研究振荡射流和分离流动的相互作用，揭示控制机理，对比控制效果。相关成果可为工程应用提供一种有效的流动控制手段。

自激振荡射流是一种较为新型的流动控制方法，无需机械运动部件就可以产生高频和高速激励，因此在高雷诺数和恶劣的工作场合有着广阔的应用前景。但是，振荡射流由于自激特性，也存在频率和流量高度耦合，难以完成独立调节等难题。为了克服振荡射流参数控制难题，首先需要揭示振荡射流自激工作机理。但是振荡器内部复杂管道和外部高速自激偏转射流对流场高精度测量和分析造成了很大挑战。本项目提出了数据互补融合方法，通过对多组缺陷数据进行融合重构，克服了振荡器内部PIV测量阴影难题；提出了基于压缩感知的去噪方法，克服了快响应PSP信噪比的问题，复现了振荡器内部复杂流场/压力场的时空演变。本项目提出全局低分辨率数据和局部高分辨率数据融合方法和拉格朗日动态模式分解方法(DMD)，分析了振荡器外部射流流动特性。通过对内部/外部流场进行精确复现和分析，申请人发现振荡器内部的涡泡结构是外部射流自激振荡的驱动力，揭示了涡泡的发展与振荡器内部反馈管道流动存在的耦合关系。基于振荡射流工作机理，本项目提出以反馈管道为突破点的新型振荡器设计思路，完成自激振荡射流的参数精细化控制。提出了三种新型振荡射流驱动器，克服自激振荡射流参数控制难题，为精确流动控制提供了基础：提出无反馈振荡器，克服射流频率受到反馈管道影响问题，将振荡频率提高3倍，从而显著提高了射流控制效率；基于无反馈设计，提出子母射流振荡器，克服射流频率和振幅与射流速度耦合难题，完成参数独立控制，为精确调节流动控制参数提供了基础；发展了并联互通振荡器，完成协同振荡射流之间的相位控制，提高了流动控制的平均性。最后，将自激振荡射流应用到航空航天领域，开发了流动控制应用新方法，包括：机翼尾涡和流动分离控制、发动机气动矢量推进技术、进气道内流流动分离抑制等，克服了传统定常射流控制效率低等难题。

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