Youjin Kim

By Youjin Kim, Ali Al-Abadi and Antonio Delgado

This chapter describes the method of airfoil optimization considering boundary layer for aerodynamic efficiency increment. The advantages of laminar boundary layer expansion in airfoil of horizontal axis wind turbine (HAWT) blades are presented as well. The genetic algorithm (GA) optimization interfaced with the flow solver XFOIL was used with multi-objective function. The power performance of turbine with optimized airfoil was calculated by using blade element method (BEM) in software QBlade. The CFD simulation from OpenFOAM® with Spalart-Allmaras turbulence model showed the visualized airflow. The optimized airfoil shows enlarged laminar boundary layer region in all flow regime with a higher aerodynamic efficiency and the increased gliding ratio (GR). The power velocity and annual energy production (AEP) curves show the performance improvement of wind turbine with the optimized airfoil. The boundary layer thickness and skin-friction coefficient values support the decreased drag of the optimized airfoil. The smaller laminar separation bubbles and reduced stall regime of CFD simulations illustrate the desirable aerodynamics of the resulted airfoil.

Part of the book: Flight Physics

By Youjin Kim, Galih Bangga and Antonio Delgado

The airfoil shape of horizontal axis wind turbine (HAWT) blade is optimized using genetic algorithm (GA). The algorithm is set to find the final airfoil shape with the highest gliding ratio (GR) and larger laminar boundary layer regime along the airfoil surface. The main aim is to find the best airfoil shape of higher lift coefficient with reduced drag in boundary layer from the reference airfoil shape. A 3D correction law is applied to model the effect of optimized airfoil in 3D rotational augmented situation. The thrust and power curves are generated by the blade element (BEM) and free vortex (FV) codes with 3D and loss correction. The higher power production is given when the wind turbine blades are designed using the optimized airfoil. This increment is thought to be made from the efficiency caused by the reduced separation bubbles from reduced turbulent boundary layer and 3D rotational augmentation. To validate its effectiveness in case of soiled condition, the aerodynamic parameters of airfoils are recalculated by enforcing the airfoil to undergo earlier transition, which models the leading edge roughness. The results indicate the soiled condition that does not affect the aerodynamic efficiency of the airfoil due to the positive effect of 3D rotation augmentation.

Part of the book: Design Optimization of Wind Energy Conversion Systems with Applications