Turbulence skin-friction reduction by traveling waves: a DNS study

Vehicles traveling in air or water, such as planes, cars or submarines, experience significant aero- or hydrodynamic drag, including pressure drag, wave drag, turbulence drag, etc. Drag reduction has attracted the attention of the research community, owing to its potential for reduction in both energy consumption and pollutant emissions. The work in this dissertation focuses on a family for turbulence skin-friction drag reduction by traveling waves, which have attracted people’s interests both from academia and industry. Although being completely based on DNS based numerical simulations, experimental practices are considered for the DBD plasma actuator implementation in this dissertation. This dissertation first reviews the wall turbulence and its link with the skin-friction drag. Then, the drag reducing and energetic performance of the flow control family based on traveling waves are discussed and assessed in detail. The effect of discretisation occurring in experiments are evaluated with numerical simulations. The last part of the thesis introduces a recently proposed flow control paradigm CPI (Constant Power Input) and studies the drag reduction problem in a turbulent pipe flow under that framework.