FOR 1779:  Active Drag Reduction by Transversal Surface Waves

• Subject Area: Thermal Engineering/Process Engineering ; Computer Science, Systems and Electrical Engineering ; Mechanical and Industrial Engineering ; Materials Science and Engineering
• Term: from 2011 to 2020
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 202175528

The total drag of transport systems such as airplanes, ships and/or trains is primarily determined by friction drag. Today's approach to reduce the viscous drag is based on stabilising the laminar state of the boundary layer flow since the wall shear stress in a laminar is drastically smaller than in a turbulent boundary layer. This idea has been pursued for more than 40 years.
The investigated active and passive measures result in a much more intricate technology and a pronounced increase of the overall weight of the transport system such that the prospective efficiency gain of any hybrid flow control system is massively lowered. A novel approach to lower friction drag is based on the hypothesis that the wall shear stress of a turbulent boundary layer can be efficiently decreased if only the near-wall coherent structures are damped, i.e., to a certain extent suppressed, by controlled surface perturbations at minimum energy impact.
This idea is the core of this Research Unit where spanwise transversal surface waves are used to efficiently redistribute the near-wall coherent structures and as such to lower the turbulence production in the boundary layer. This controlled interaction between the flexible structure and the near-wall fluid leads to a stabilisation of the near wall streaks and, thus, to a lower friction drag. Overall, this project belongs to the field of a joint fundamentally and technologically oriented turbulence research approach.

• DFG Programme: Research Units

Projects

• Development of a real-time actuator and sensor network (Applicant van Waasen, Stefan )
• Experimental analysis of friction drag above moving surfaces (Applicant Schröder, Wolfgang )
• Forming of large-area metallic riblet surfaces (Applicant Hirt, Gerhard )
• Numerical analysis of friction drag above moving surfaces (Applicant Schröder, Wolfgang )
• Numerical fluid-structure coupling schemes for high-frequency surface motion (Applicant Dahmen, Wolfgang )
• Reduction of friction drag in subsonic flow via feedback control (Applicant Abel, Dirk )
• Very-High-Cycle Fatigue of structured surfaces (Applicant Beck, Tilmann )
• Zentralprojekt (Applicant Schröder, Wolfgang )

• Spokesperson: Professor Dr.-Ing. Wolfgang Schröder