Römer, Tristan M.Schulz, Kai A.Wu, YongxiangWenzel, ChristophRist, Ulrich2025-03-2020231432-11140723-48641923502530http://nbn-resolving.de/urn:nbn:de:bsz:93-opus-ds-160420https://elib.uni-stuttgart.de/handle/11682/16042https://doi.org/10.18419/opus-16023Delaying laminar-turbulent transition in boundary layers is of great interest since the skin-friction coefficient can be reduced by up to one order of magnitude. In this experimental research, it is shown that counter-rotating cylindrical roughness elements are able to delay transition under realistic flow conditions. Evidence is given by the intermittency, evaluated from hot-film measurements in a laminar water channel. An increase in rotation speed results in a delay of transition of up to 6.5%in the center of the plate. This trend can be explained by the streaks amplified by the rotating cylinders, resulting in a damping of the fluctuation amplitude in the boundary layer. The advantage of this method is that the transition delay can be actively controlled with conventional cylindrical roughness elements.enCC BYinfo:eu-repo/semantics/openAccesshttps://creativecommons.org/licenses/by/4.0/620article2024-11-02