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Active Control of Turbulent Flow Separation by Surface Plasma

表面等离子体湍流分离的主动控制

基本信息

批准号：
EP/D500850/1
负责人：
Kwing-So Choi
金额：
$ 24.06万
依托单位：
University of Nottingham
依托单位国家：
英国
项目类别：
Research Grant
财政年份：
2006
资助国家：
英国
起止时间：
2006 至无数据
项目状态：
已结题

来源：
https://gtr.ukri.org/projects?ref=EP%2FD500850%2F1
关键词：
Active Control Turbulent Flow Separation

项目摘要

Radio frequency glow discharges are been used in microelectronic device fabrication, ozone generation and in gas laser excitation. Such discharges operating at atmospheric pressure have been shown to produce jet flows to be used for flow control. Some of recent results obtained from our laboratory clearly confirmed these claims. Surface plasma actuators are simple device with no moving parts or ducting, which have high frequency response and thus have a realistic possibility for aeronautical applications. Already, tests have been conducted for airfoils and turbine blades for possible control of transition, skin-friction drag and flow separation in the last year of so. However, there is still a lack of information on surface plasma physics and associated fluid dynamics to fully utilise the devices for flow control. The production mechanism of wall jets by surface plasma is not well understood, nor is the optimum condition for plasma excitation in flow control. These are precisely the reasons why we propose this research, so that we can advance our understanding on surface plasma for many aeronautical applications, flow separation control in particular.In this investigation we would like to study active control of flow separation during static and dynamics stall. Control of static stall can be investigated by placing surface plasma actuators before the separation point over a circular cylinder with a view to delay flow separation. Here, the time averaged lift and drag forces should indicate the effectiveness of separation control. Control of dynamics stall over a lifting surface can be carried out by reducing the area of separation region or even to recover from separation by using surface plasma actuator. Novelty of this approach is that a real-time detection of flow separation over the body surface is not required, as the vortices are periodically shed from the cylinder surface. Besides, the flow around a circular cylinder is a subject that has been studied by many researchers, therefore there are enough database to help validate our baseline measurements.PIV (Particle Image Velocimetry) system is becoming a common flow measurement technique in fluid dynamic research in recent years, where an entire velocity field in a light-sheet plane can be obtained. With PIV system, small particles in the flow shone by the laser light sheet are photographed in a short interval with a digital camera. The distance and direction of movement of each flow particle gives the velocity vector, thereby globally mapping the velocity field. In our study, flow images will be captured at 1 kHz at a full camera resolution of 1600x1200 pixels for 8 seconds, with 20 mJ of energy being produced by the laser. All of these equipments will be made available from EPSRC Engineering Instrument Loan Pool for this study. The PIV measurements will be complimented by other techniques, such as hot-wire measurements and flow visualisation, which will give confidence in our results, add insight into vortical structures during flow separation and provide better understanding of the mechanisms in which flow separation control with surface plasma can be carried out.

射频辉光放电被用于微电子器件制造、臭氧产生和气体激光激发。这种在大气压下工作的放电已被证明会产生用于流量控制的射流。最近从我们实验室获得的一些结果清楚地证实了这些说法。表面等离子体激励器是一种简单的器件，没有运动部件或导管，具有很高的频率响应，因此在航空应用中具有现实的可能性。在SO的最后一年，已经对翼型和涡轮叶片进行了可能的过渡控制、表面摩擦阻力和流动分离的测试。然而，仍然缺乏关于表面等离子体物理和相关流体动力学的信息，以充分利用这些设备进行流动控制。表面等离子体产生壁面射流的机理还不是很清楚，流动控制中等离子体激发的最佳条件也不是很清楚。正是由于这些原因，我们提出了这项研究，以促进我们对表面等离子体在许多航空领域的应用，特别是流动分离控制的理解。在这项研究中，我们想要研究静态和动态失速过程中流动分离的主动控制。控制静态失速的方法是在圆柱上方的分离点前放置表面等离子体激励器，以延缓流动分离。这里，时间平均升力和阻力应该表示分离控制的有效性。通过减小分离区的面积来控制升力面上的动态失速，甚至可以利用表面等离子体激励器从分离中恢复。这种方法的新奇之处在于，不需要对物体表面的流动分离进行实时检测，因为涡流是周期性地从气缸表面脱落的。此外，圆柱体的绕流是许多研究人员一直在研究的课题，因此有足够的数据库来验证我们的基线测量。近年来，PIV(粒子图像测速)系统正在成为流体力学研究中一种常用的流动测量技术，它可以获得光片平面内的整个速度场。利用PIV系统，用数码相机在短时间间隔内拍摄激光光片照射下流动中的细小颗粒。每个流动粒子的移动距离和方向提供了速度向量，从而全局映射速度场。在我们的研究中，流动图像将在1600x1200像素的全相机分辨率下以1 kHz的速度拍摄8秒，其中激光产生20mJ的能量。所有这些设备都将从EPSRC工程仪器贷款池中获得，用于本研究。PIV测量将与其他技术相辅相成，如热线测量和流动可视化，这将使我们的结果更有信心，增加对流动分离过程中的涡旋结构的洞察，并更好地了解利用表面等离子体进行流动分离控制的机制。