Plasma-actuator controlled turbulent jets

航空和航空运输是我国社会和经济的一个重要部门。目前，航空业约占人类造成的二氧化碳排放量的2%，去年全球客运量超过31.2亿人次，货运量超过4800万吨，平均每天有超过10万个航班。预计未来30年，全球交通流量将以每年4%至5%的速度增长。这仅仅意味着到2050年，预计将有超过160亿乘客和2500万次航班。航空业必须找到方法来满足日益增长的航空运输需求，同时减少对环境的影响，特别是噪音和碳排放水平。还需要创新的解决方案来处理燃料消耗，这样航空业就不会越来越依赖越来越昂贵的能源。很明显，这要求未来飞机的技术发生重大变化。近年来，被称为等离子体致动器的设备的发展推动了以增加升力、减少阻力和提高空气动力学效率的新方式控制流动的前景，这些进步可能会导致更安全、更高效和更安静的飞机。介质阻挡放电（DBD）等离子体致动器由两个电极组成，一个电极暴露在环境流体中，另一个电极被介电材料覆盖。当在两个电极之间施加交流电压时，覆盖电极上的环境流体电离。这种电离的流体被称为等离子体，并产生一个与周围中性带电流体交换动量的体力矢量。在这个项目中，将在欧洲最强大的超级计算机上进行高分辨率模拟，以证明DBD等离子体致动器控制湍流射流的潜力。在过去的几十年里，由于航班数量的不断增加，环境影响法规的收紧，以及城市/住宅区在机场附近的发展，飞机噪音污染问题变得更加严重。本项目的科学目标是提高我们对气动声学机制的理解，使我们能够提出针对自由剪切流的有针对性的等离子体控制策略，以解决射流噪声污染问题。这个研究项目是在航空领域发展基于等离子体致动器的新技术的第一步，不仅是为了降低噪音，而且有可能用于增强混合和提高喷气发动机的效率。截至目前，主动流量控制技术尚未在商用飞机上实施。影响等离子体致动器性能的大量参数（致动器的位置、方向、尺寸、嵌入和暴露电极的相对位置、施加电压、频率）使其开发、测试和优化成为一项非常复杂的任务。实验方法需要大量高成本和耗时的试错迭代。计算流体动力学（CFD）可以补充理想的实验，具有研究等离子体致动器控制的湍流的详细潜力。

Aeronautics and air transport is a vital sector of our society and economy. Aviation currently accounts for about 2% of human-induced CO2 emissions with more than 3.12 billion passengers and 48 million tons of freight worldwide last year with an average of more than 100,000 flights every day. Worldwide traffic is predicted to grow at a rate of 4% to 5% per year for the next 30 years. It simply means that more than 16 billion passengers and 25 million flights are expected in 2050. Aviation will have to find ways to meet the growing demand for air transport whilst reducing its environmental impact, specifically the level of noise and of carbon emissions. Innovative solutions are also needed to deal with fuel consumption so that aviation does not become increasingly dependent on more and more expensive energy sources. It is clear that it requires a significant step change in the technologies of future aircraft.In recent years, the development of devices known as plasma actuators has advanced the promise of controlling flows in new ways that increase lift, reduce drag and improve aerodynamic efficiencies, advances that may lead to safer, more efficient and quieter aircraft. Dielectric barrier discharge (DBD) plasma actuators consist of two electrodes, one exposed to the ambient fluid and the other covered by a dielectric material. When an A.C. voltage is applied between the two electrodes the ambient fluid over the covered electrode ionizes. This ionized fluid is called the plasma and resultsin a body force vector which exchanges momentum with the ambient, neutrally charged, fluid. For this project, high-resolution simulations will be carried out on the most powerful supercomputers in Europe in order to demonstrate the potential of DBD plasma actuators for the control of turbulent jets. The problem of jet noise pollution has become more severe in the past few decades due to the ever increasing number of flights, the tightening of environmental impact regulations, and the development of urban/residential areas in close proximity to airports. The scientific objective of the present project is to advance our understanding of aeroacoustic mechanisms up to the point where we canpropose targeted plasma control strategies for free shear flows to tackle the problem of jet noise pollution. This research project is a first step in the development of new technologies based on plasma actuators in the aeronautic sector not only for noise reduction purposes but also potentially for mixing enhancement and for a better efficiency of jet engines.As of today, active flow control technologies have not been implemented in commercial aircraft. The large number of parameters (location of the actuator, orientation, size, relative placement of the embedded and exposed electrodes, applied voltage, frequency) affecting the performance of plasma actuators makes their development, testing and optimisation a very complicated task. Experimental approaches require numerous high-cost and time consuming trial-and-error iterations. Computational Fluid Dynamics (CFD) can complement ideally experiments with the potential to investigate indetail plasma-actuator controlled turbulent flows.