Experimental studies and control of wall-bounded and separated shear layers using active flow control

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The impacts of commercial aviation on the environment are serious, widespread and long-lasting. Areas near airports are subject to noise pollution during takeoff and landing. The emissions created by burning jet fuel cause air pollution and, over decades, climate change: commercial aviation produces 4.9% of the total human contribution to global warming according to the IPCC. The International Air Transport Association (IATA) policy is to achieve carbon neutral growth in commercial aviation by 2020, and reduce carbon dioxide emissions by 50% by 2050. Reducing environmental impact is the crucial challenge in the design of future aircraft. In order for the Canadian aerospace industry, which generates $23.6 billion in revenue annually, to remain globally competitive, step changes in technology are required. One such technology is active flow control, which has been identified by the Advisory Council for Aeronautics Research in Europe (ACARE) as a key factor to produce the technologies required to meet the stringent environmental targets set on the aerospace industry.The proposed research is aimed at the development and implementation of novel active flow control strategies with an emphasis on flow fields that are relevant to the Canadian aerospace industry. It will focus on boundary layer transition, as a precursor to controlling turbulent boundary layers, and shear layer separation. The importance of these flows is related to their impact on drag and noise production in a wide range of engineering systems. Notably, the skin friction drag due to a turbulent boundary layer is ten times larger than for the equivalent laminar boundary layer. In the case of separation, the resulting wake and periodic flow structures lead to undesired pressure drag and fluctuating aerodynamic loads. Both turbulent boundary layers and separated shear layers are responsible for increased noise emissions. Therefore, the delay of transition, control of turbulence and management of separated flows can lead to significant reduction in drag and noise emissions.The methodology proposed is to leverage basic flow dynamics and instabilities to develop efficient closed-loop controllers. This aspect is closely linked with the development of sensors and actuators to enable the control systems. These control systems will be implemented and tested in an experimental framework. Therefore, the research is not limited to the study of the fluid flows and their control, but also addresses key practical challenges associated with the application of active flow control in real life. The practical ramifications of this research are wide ranging. They include the reduction of drag, fuel consumption and noise emissions in a variety of commercially relevant fluid systems. These benefits will lead to a reduction in our dependence on fossil fuels and a decrease in greenhouse gas emissions. The proposed work is multidisciplinary, as it draws upon expertise in the areas of fluid dynamics, feedback control and dynamical systems. It is also transformative, since it addresses open questions that, in the long term, should lead to a paradigm shift not only with respect to engineering practices in the management of fluid flows related to energy-conversion devices and transportation, but also to the design practices for energy efficiency of these engineering systems.The proposed research will involve 2 PhD, 3 MASc and 5 undergraduate students. These students will gain skills and expertise that are in high demand in many technological sectors in Canada, in particular the aerospace industry. Canadian companies such as Bombardier Aerospace and Pratt & Whitney Canada will benefit directly from both the proposed research and the highly qualified personnel that it will train.