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

航空航天部门在加拿大经济中发挥着重要作用。2017年，中国创造了约250亿美元的国内生产总值和近19万个高薪就业岗位。在航空业的具体情况下，气候变化和噪音污染是该行业面临的一些最重大的挑战和风险。为了保持加拿大航空航天工业的全球竞争力，需要在技术上进行逐步变革。主动流量控制是国际航空运输协会(IATA)认为有助于满足航空航天工业严格环境目标的技术之一。拟议的研究将开发和实施新的主动流量控制策略，重点放在与加拿大航空航天工业相关的流场上。要研究的具体主动流动控制目标是：(I)减少湍流边界层造成的壁面摩擦阻力，以及(Ii)尾迹控制以减少钝化后缘翼型的压力阻力和噪声排放。*(1)以前的研究表明，通过主动控制近壁湍流，湍流边界层中的壁面摩阻减少了约30%。然而，最近的研究表明，这些好处不会随着飞行雷诺数的增加而扩大。这一建议将考虑一种通过操纵对数区域中存在的大的相干结构来控制湍流边界层的新方法。众所周知，这些结构在较大的雷诺数时变得更占优势，并且由于其尺寸比近壁结构更大，可以提供一种更实用的实现途径。*(2)后缘钝化的翼型在航空航天工业中很常见，因为它们可以提供优越的升阻比和改善结构完整性。然而，与此相关的尾迹会导致更高水平的压力阻力、脉动气动力和噪声。申请者的初步研究表明，采用钝化后缘流线型机身的有效主动流动控制方法可使尾流中的压力阻力减少约30%，并减少90%以上的不稳定性。建议将这种方法扩展到钝化后缘翼型，从而使其更接近工业应用。这将为这些翼型带来显著更好的性能。*这项研究的实际影响是重大的和广泛的。它们包括减少各种商业相关流体系统的阻力、燃油消耗和噪音排放。这些好处将导致航空航天工业减少对化石燃料的依赖，并减少温室气体排放。这项研究也具有变革性，因为它解决了一些悬而未决的问题，从长远来看，这些问题应该会导致关于流体系统能源效率和减少污染的设计实践的范式转变。

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.**