Digital Library of the European Council for Modelling and Simulation

Title:	Numerical Supported Design Of Continuously Adapted Riblets For Viscous Drag Reduction On A NREL Wind Turbine Airfoil
Authors:	Karsten Oehlert, Jan H. Haake, Konrad M. Hartung
Published in:	(2018). ECMS 2018 Proceedings Edited by: Lars Nolle, Alexandra Burger, Christoph Tholen, Jens Werner, Jens Wellhausen European Council for Modeling and Simulation. doi: 10.7148/2018-0005 ISSN: 2522-2422 (ONLINE) ISSN: 2522-2414 (PRINT) ISSN: 2522-2430 (CD-ROM) 32nd European Conference on Modelling and Simulation, Wilhelmshaven, Germany, May 22^nd – May 26^5h, 2018
Citation format:	Karsten Oehlert, Jan H. Haake, Konrad M. Hartung (2018). Numerical Supported Design Of Continuously Adapted Riblets For Viscous Drag Reduction On A NREL Wind Turbine Airfoil, ECMS 2018 Proceedings Edited by: Lars Nolle, Alexandra Burger, Christoph Tholen, Jens Werner, Jens Wellhausen European Council for Modeling and Simulation. doi: 10.7148/2018-0366
DOI:	https://doi.org/10.7148/2018-0366
Abstract:	Viscous drag is a significant factor contributing to the efficiency of aerodynamic application. During the last decades several studies have shown that func-tional surface structures provide the potential to re-duce the viscous drag in the turbulent boundary layer and thus increase efficiency. Due to the rather chal-lenging manufacturing process of micro-scale riblets most studies were conducted using constant riblet dimensions causing losses of the possible drag reduc-tion. With the rapid development in micro struc-turing technologies it is now possible to manufac-ture continuously adapted riblets in almost indus-trial processing scales. For the design of continuously adapted riblets an algorithm is developed consider-ing the effect of a deviation of the riblet spacing from its theoretical optimal value in order to maximize the cumulative drag reduction additionally effected by a misalignment of the riblet structure. The algorithm is applied for the design of riblets with a trapezoid cross-section for the NREL wind turbine airfoil S809 at a Reynolds number of Re = 2 · 106. The shear stress data required to determine an appropriated re-gion for the riblet application and optimal riblet di-mensions are provided by 2D numerical studies using an empirical three equation transition model which shows good consistency of the predicted location of the transition onset with experimental results. With the outlined design approach an increased drag re-duction in rage of 25.7% compared to riblets with constant dimensions can be expected.
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