Plasma-actuator controlled turbulent jets

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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.