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

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The aerospace sector plays an important role in the Canadian economy. In 2017, it accounted for approximately $25 billion in GDP and nearly 190,000 high-paying jobs. In the specific case of aviation, climate change and noise pollution represents some of its most significant challenges and are risks to the industry. In order for the Canadian aerospace industry to remain globally competitive, step changes in technology are required. Active flow control is one of the technologies considered to help meet the stringent environmental targets set on the aerospace industry by the International Air Transport Association (IATA). The proposed research will development and implementation novel active flow control strategies with an emphasis on flow fields that are relevant to the Canadian aerospace industry. Specific active flow control objectives to be investigated are: (i) reduction of skin-friction drag due to turbulent boundary layers, and (ii) wake control to decrease the pressure drag and noise emissions from blunt trailing edge airfoils. (1) Previous studies demonstrated ~30% reduction in skin friction in turbulent boundary layers through active control of the near-wall turbulence. However, recent works suggests that these benefits would not scale to flight Reynolds number. A new approach of controlling the turbulent boundary layer through the manipulation of the large coherent structures present in the log-region will be considered with this proposal. These structures are known to become more dominant at large Reynolds number and can offer a more practical pathway to implementation given their larger sizes compared to the near-wall structures. (2) Airfoils with blunt trailing edges are common in the aerospace industry since they can provide superior lift to drag ratios and improved structural integrity. However, the wake associated with these causes higher levels of pressure drag, fluctuating aerodynamic forces and noise. Preliminary studies by the applicant with a blunt trailing edge streamlined body demonstrated an effective active flow control methodology that produced a reduction in pressure drag of approximately 30% and over 90% less unsteadiness in the wake. It is proposed to take this methodology closer to industrial application by extending its use to blunt trailing edge airfoils. This will lead to significant better performance for these airfoils. The practical ramifications of this research are significant and 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 the aerospace industry's dependence on fossil fuels and a decrease in greenhouse gas emissions. The research is also transformative since it addresses open questions that, in the long term, should lead to a paradigm shift with respect to the design practices for energy efficiency of, and pollution reduction from, fluidic systems.