【作者】 高峰；

【导师】 汪亮；

【作者基本信息】 西北工业大学 ， 航空宇航推进理论与工程， 2003， 博士

【摘要】 以微电子机械系统(MEMS)、混沌论及非线性复杂大系统不稳定理论为基础，一种全新的流场主动控制技术——微射流技术应运而生。作为一种全新的流场主动控制手段，微射流是通过其微尺度扰动同宏观大尺度流动的整体耦合作用达到控制宏观流动的目的。微射流控制系统简单、轻便、能耗极小且不需要工质源，初步显示出了常规射流控制方法所不具备的优势，具有非常广阔的应用前景。本文对微射流及其与主射流的合成流场进行数值模拟和机理分析，为微射流技术的工程应用研究打下基础。 本文的主要研究成果如下： 1．通过对微射流与主射流合成流场的深入分析，分别建立了微射流作动器二维、三维可压外流场控制方程以及二维微射流与主流合成流场的控制方程。采用快速求解的近似隐式因式分解法(AF方法)并内置似牛顿子迭代，有效地抑制了数值振荡、提高了稳定性并恢复了非线性方程在线化过程中所丢失的一些重要特性，同时还消除了因使用显式边界条件、人工粘性及隐式一边使用低阶空间差分近似所带来的误差。显式一边的空间导数采用具有较高精度和良好数值稳定性的隐式高阶紧致差分格式，同时采用适于低马赫数流动计算的隐式高阶数值过滤方法。 2．分别采用层流、湍流模型对单微射流流场进行了数值模拟。模拟结果显示了微射流的产生、形成、发展与耗散过程以及微射流的卷吸特征等。分析了双微射流作动器在不同频率、相位下协调工作时所形成的合成流场的特征。“低压回流区”的细观分析诠释了微射流的作用机制。 3．三维微射流流场的数值模拟再现了实验所观察到的旋涡对的生成、发展及其相干性的消失过程；揭示了旋涡对沿展向的不稳定性是旋涡对相干性消失的主要原因。在三维数值模拟中还捕捉到了二次涡，这为以后进一步研究微射流旋涡对的细微结构打下了良好的基础。 4．微射流与主射流合成流场的数值模拟再现了实验所观察到的主射流流动方向发生偏转的情形；分析了在“拉”模型单、双微作动器模式下，微射流控制宏观流动的现象及内在机理；揭示了微射流与主流之间“低压回流区”所引起的主流通道内的压力分布不平衡是主射流宏观流动方向发生偏转的西北工业大学博士学位论文Ph.D.Dissertation ofNorthwesternPolyteehnieal University 内在原因。分析了“拉”模型单作动器模式下，微射流作动器的入射角度、 驱动频率、速度幅值及与主射流间的距离对主射流偏转程度的影响，并确定 了作动器工作参数的最佳范围;分析了“拉”模型双作动器模式下，不同的 相位差对主流偏转程度的影响。5.数值模拟再现了微射流改变绕流圆柱气动性能的情形。相邻微作动器同相工 作时部分分离流重新附面、尾流区减小。相邻微作动器存在相位差时，圆柱 上下表面压力系数的差值发生改变，进而使绕流圆柱的气动性能发生变化。 微作动器放置的位置不同，对圆柱气动性能的影响亦不同。微作动器放置在 分离点附近时对圆柱的气动性能影响较大。更多还原

【Abstract】 A new method for active control of flow field appears. It is the so-called microjet technology. Its fundamental principle is based on the MEMS, the chaotic theory and non-linear complicated system theory. The mechanism of active flow direction control is the microjet’s microscale disturbance coupling with the macroscale’s flow through collective interaction. The microjet is a zero net mass-flux and doesn’t require internal source of jet fluid. Its control system is simple, light and little energy consumed. Microjet is superior to conventional jet. So this dissertation studies the microjet flow field and the synthetic flow field of the microjet and the mean flow by numerical simulation. The main research results in the dissertation are as follows:1. According to the characteristics of the microjet and the synthetic flow field, the unsteady, two/three dimensional, compressible N-S equations were used for the flow field simulation. Time-accurate solutions to N-S equations were obtained by the implicit approximately-factored(AF) finite-difference algorithm. Newton-like subiterations were used within a time step to reduce errors due to factorization, linerization and explicit application of boundary conditions. Numerical fluxes considered in the explicit portion of the algorithm were evaluated by an implicit high-order compact scheme to augment stability. Meanwhile, an implicit high-order compact numerical filter was used.2. The laminar/turbulence models were used to simulate the single microjet flow field. The result shows the periodic characteristics of microjet flow field including vortex pair evolution, immigration and dissipation process. The synthetic flow field of two adjacent microjet actuators and its evolvement with time, as well as different working frequencies and relative phase angles were numerically simulated. The "low pressure closed recircular flow region" was analyzed to explain the characteristics of the synthetic flow field.3. The 3D simulation result shows characteristics as well as creating, developing and dissipation process of the microjet. The results show good agreement withexperimental results. The numerical study reveals the spanwise instability of vortex pairs, resulting in the breakdown of the coherent vortex structure. Especially the secondary vortex is also captured.4. Vectoring of a primary jet with a single or two adjacent microjets in a pull mode was numerically investigated. The result shows the primary jet can be vectored and trends towards the microjet actuators. Analysis indicates the "low pressure closed reticular flow region" results in the non-equilibrium of pressure along the primary jet’s orifice. To obtain as large vectoring angle as possible, the optimal ranges of angles, frequencies, velocity amplitudes, and distances from the microjet actuator to the primary jet exit were discussed. The relationship between the vectoring angle of the primary jet and the phase-difference of two adjacent actuators was analyzed.5. The modification of the aerodynamic force performance on a 2D cylinder by use of microjet was numerically simulated. The result shows that the pressure distribution on the cylinder and the wake are modified, and the separate flow partially is attached to the surface again.更多还原