Emmy Noether Research Group
The research group Viscous Flow Control is an independent junior research group funded by the Emmy Noether programme of the German Research Foundation (DFG). It is part of the Cluster of Excellence “Smart Interfaces – Understanding and Designing Fluid Boundaries” (CSI) at the Technische Universität Darmstadt. Within the CSI we are directly linked to the young researcher group “Drag and Circulation Control”. We are presently setting up a new experimental facility in order to investigate the drag reducing performance of the new structured surfaces that are manufactured at the Microprototyping Center (PTW) of TU Darmstadt.
Viscous Flow Control
In general, flow control describes the process of assigning a desired property to a fluid flow. The flow property that we are trying to influence and control is the viscous drag or skin friction drag. It refers to the flow resistance which limits the fluid flow rate through a pipe or generates the forces that oppose the motion of a solid through fluid. A reduction of the flow resistance has a huge potential in respect to energy savings and reduced emission. In general we distinguish different types of drag which, depending on the flow situation, are of varying importance.
Skin friction drag forms the highest contribution to the overall flow resistance in many practical applications. It is caused by the momentum loss from the fluid to the wall. When a flow approaches a solid wall it is suddenly decelerated and thus transfers a significant part of its momentum to the wall. In turbulent flows the existing eddies continuously move new fluid towards the wall and the resulting viscous drag is much higher than in laminar flows. Therefore, two different approaches can be taken to reduce the viscous drag:
- Delay of laminar to turbulent transition.
- Reduction of the skin friction drag in turbulent flows.
We investigate the possibilities of viscous drag reduction using theoretical and numerical tools and aim at the development of innovative surface structures which influence the momentum transport from the fluid to the wall and thus enable viscous drag reduction.