Delay of laminar–turbulent transition by counter-rotating cylindrical roughness elements in a laminar flat plate boundary layer

Abstract Delaying laminar–turbulent transition in boundary layers is of great interest since the skin-friction coefficient can be reduced by up to one order magnitude. In this experimental research, it shown that counter-rotating cylindrical roughness elements are able delay under realistic flow conditions. Evidence given intermittency, evaluated from hot-film measurements a laminar water channel. An increase rotation speed results $${6.5}{\%}$$ 6.5 % center plate. This trend explained streaks amplified rotating cylinders, resulting damping fluctuation amplitude layer. The advantage method actively controlled with conventional elements. Graphical abstract