Assessment of the dimples as passive boundary layer control technique for laminar airfoils operating at wind turbine blades root region typical Reynolds numbers

Abstract

In this work we consider dimples as a possible passive boundary layer control strategy in order to improve the wind turbine blades performance. Due to the complexity of the phenomenon, Large–Eddy Simulation (LES) is here used to analyze the flow field induced by dimples on the NACA 642–014A laminar airfoil operating at Re=1.75⋅105. We have selected a laminar airfoil since this kind of airfoils has been considered as successful solution for modern utility–scale wind turbines. Experimental measurements were also carried out at the Environmental Wind Tunnel of the “Università Politecnica delle Marche” for the sake of validation of our numerical investigations. LES results provided a good agreement with experimental data. It has been shown that dimples application can produce a reduction of the boundary layer separation; additionally, in all the considered cases, dimples reduce the pressure drag coefficient with a consequent increase of the viscous drag coefficient.