Year: 2025
Type: article
Abstract: Delaying the laminar–turbulent transition of a boundary layer reduces the skin-friction drag and can thereby increase the efficiency of any aerodynamic device. A passive control strategy that has reaped success in transition delay is the introduction of boundary layer streaks. Surface-mounted vortex generators have been found to feature an unstable region right behind the devices, which can be fatal in flow control if transition is triggered, leading to an increase in drag with respect to the reference case without devices. In a previous proof of concept study, numerical simulations were employed to place artificial vortices in the free stream that interact with the boundary layer and accomplish transition delay. In the current study, we present experimental results showing the feasibility of generating free-stream vortices that interact with the boundary layer, creating high- and low-speed boundary layer streaks. This type of streaky base flow can act as stabilizing if introduced properly. We confirm the success of our flow control approach by artificially introducing two-dimensional disturbances that are strongly attenuated in the presence of streaks, leading to a transition delay with respect to the reference case of approximately 40 %.
Source: Journal of Fluid Mechanics
DOI: 10.1017/jfm.2025.336
Authors: André Weingärtner, Zhuxuan Cui, Imge Yigili, Jens H.M. Fransson
Institution: KTH Royal Institute of Technology
Language: English
Subfield: Computational Mechanics
Field: Engineering
Domain: Physical Sciences
Open Access status: hybrid
Estimated APC paid: $3,550
OpenAlex ID: W4410187927