Pushing the Limits: Enhancing Turbomachinery Efficiency by Riblet Application

The reduction in aerodynamic drag remains a crucial pathway for enhancing turbomachinery efficiency. Riblet structures are a well-established passive technique to reduce viscous drag, but their application has been constrained by the challenge of adapting size and orientation to match the local flow conditions. This study presents a novel laser-based fabrication process developed at the Laserinstitut Hochschule Mittweida, which enables the production of continuously adapted riblets on complex curved surfaces. Numerical simulations were employed to design riblet patterns for the NACA0012 airfoil at zero angle of attack, followed by laser manufacturing and high-resolution surface characterization. Aerodynamic performance was evaluated through wake surveys in a Göttingen-type wind tunnel at the Jade University of Applied Sciences. The results validate the numerical design approach and show that tailored riblet structures provide a notable improvement in drag reduction compared to constant geometries, with relative gains of about 8% for the one-sided and 16% for the two-sided application. These findings underline the potential of advanced laser-based manufacturing processing to enable riblet integration in turbomachinery under industrially relevant conditions.