【作者】 周勇；

【导师】 王鑫伟； 王帮峰；

【作者基本信息】 南京航空航天大学 ， 测试计量技术及仪器， 2009， 博士

【摘要】 合成射流技术是一种全新的流场主动控制方法,它通过驱动隔膜的周期振动改变驱动器腔体体积,从而在出口处形成射流,其特点是在驱动器吹出和吸入流体的一个周期内,出口净质量流量为零,但净动量不为零。它能够以局部很小的能量输入实现全局大尺度的流场控制,因此被认为是流场控制的突破性技术,成为流场控制领域的一个重要研究方向,同时在航空航天等领域也具有重要的应用前景。本文立足于合成射流技术的基础性研究,通过数值仿真和试验着重研究了合成射流产生的机理和发展演化过程。探索了一种旨在提升驱动器的驱动能力的新型半钹形压电-金属复合结构隔膜。此外,为了有效地分析和处理试验中得出的非稳态流场信号,采用了一种新的信号分析处理方法。具体的研究内容有:第一,基于二维不可压缩RANS方程建立数值模型,研究了现有几种湍流模型在描述合成射流现象时的适用性。分别应用这些模型数值模拟合成射流流场,并与试验结果进行对比,确定了最佳模型。第二,利用选定的湍流模型数值仿真了合成射流的产生机理、射流和涡对的运动演化过程,研究了射流速度场在时间和空间上的分布特性、合成射流驱动器输出射流速度与腔体结构参数、出口形状以及出口的倾斜角度等的关系,为驱动器腔体结构的优化设计提供了参考。第三,为了提高振动隔膜的驱动能力,提出了一种新型的半钹形压电-金属复合结构振动隔膜。使用商业有限元软件ANSYS建立了隔膜的有限元分析模型,分析了隔膜的动态特性,并通过仿真对隔膜结构及其尺寸进行了研究。此外,还提出了另一种新型半钹形双隔膜驱动器。通过对隔膜的试验测试表明半钹形隔膜的位移变形量达到传统平板形隔膜的2.6倍。第四,制作了几种半钹形隔膜以及传统平板形隔膜合成射流驱动器,并对其进行了试验测试,利用总压管测速、热线测速法以及粒子图像测速法测量了合成射流的流场分布特性。对驱动器的腔体尺寸进行了优化,验证了数值仿真研究的正确性。试验结果也表明半钹形隔膜能够达到提升驱动器出口速度的目的,因而增强了驱动器的驱动能力。最后,将Hilbert-Huang变换引入到流场的信号处理中。对热线风速仪所测射流瞬时速度信号进行HHT分析和处理,其结果具有清晰的物理意义,从而表明HHT可以有效地应用于流场信号的分析与处理中。本论文的研究得到了国家自然科学基金的资助(项目号:90405008)。更多还原

【Abstract】 The synthetic jet technology is a new method of active flow control. The jet is synthesized at the outlet of the actuator cavity through its volume variations caused by periodic membrane oscillations. Within a cycle of the fluid in and out of the cavity, the net mass flux is zero but the net momentum is non-zero. Controlling the flow in relatively large area can be realized by a small, localized energy input. Thus the technology, regarded as a breakthrough in flow control, has become an important research direction in the areas of active flow control and will be found applications in aerospace engineering.This dissertation aims at the fundamental research on synthetic jet technology. Emphasizes have been placed on the mechanism of the formation and evolution of synthetic jet via numerical simulations and experiments. To enhance the driving ability of the actuator, a new half cymbal piezoelectric-metal composite membrane is explored. Besides, to effectively process the non-stationary signal of the synthetic jet recorded during the experiment, a new signal processing method is employed. The detailed research is including:Firstly, a two dimensional incompressible RANS model is established. Several existing viscous models are studied for the suitability to describe the synthetic jet phenomena. Numerical simulations are conducted by utilizing these viscous models, and the simulated results are compared with experiment data to determine the best suitable model. Secondly, the formation mechanism and the evolution process of the synthetic jet are simulated numerically with the chosen model. The behavior of the time and spatial distributions of the jet velocity are investigated. Relationships of the output velocity with the cavity geometry, the outlet shape, as well as the tilt angle between the outlet centerline and the wall are studied to provide a reference for the optimization design of the actuator cavity structure. Thirdly, a new kind of half cymbal piezoelectric-metal composite membrane (HCPCM) is proposed in order to improve the driving ability of the membrane. A finite element model of the HCPCM has been established and its dynamic behaviors are analyzed by using the commercial FE software ANSYS. The membrane structure is optimized based on the finite element simulations. Besides, another new kind of actuator with dual HCPCM is also proposed. Experiments have been performed. Experimental results reveal that the displacement of the HCPCM is approximately 2.6 times larger than that of conventional plane membrane. Fourthly, based on the gathered information, several synthetic jet actuators with HCPCM and traditional plane membranes are manufactured and tested. The jet flow field is measured by using the pitot anemometer, Hot Wire Anemometer (HWA) and Particle Image Displacement Velocimetry (PIV). The optimized geometry of the actuator is also determined by the experiments. Measured data verify the correctness of the simulations. Results also reveal that the HCPCM does raise the synthetic jet velocity at the outlet and thus enhance the driving ability of the actuator. Finally, Hilbert-Huang Transform (HHT) is introduced into the signal analysis of fluid field. Signals of the instantaneous jet velocity are collected by using the HWA and are then processed with HHT. The processed results provide clear physical meanings of the jet. It may conclude that HHT is an effective method for the processing of signals in the flow field.The research is financially supported by the National Science Foundation of China (No: 90405008).更多还原