CFD challenges in the wind energy field
The past two decades have seen a dramatic growth in the use of CFD in the wind energy sector and this growth will continue as CFD numerical methods improve and large-scale computations become more economical. Having the advantage of being infinitely scalable, CFD methods can be used as a validation tool, providing a deeper understanding of aerodynamic and acoustic turbine performance which wind tunnels cannot always offer. Additionally, CFD adds value in the early phases of wind energy projects, with design optimization and identification of the maximum lift-to-drag ratio at operating angles of attack.
CFD tools are expected to give a sound response to the many remaining challenges that face engineers in the development of wind turbine technologies. CFD codes must be able to deliver results that capture the complex interactions of multiple lift forces, 3-D viscous boundary layers and wakes, secondary flows and associated vortices, and wake impingement of surrounding blade rows. To achieve such detail, fully unsteady turbulent simulations around the blades and sliding mesh computations cannot be neglected. Considerable computational resources are often necessary to obtain grid independent solutions for the three-dimensional, unsteady flow fields of rotors and operating turbines, which necessitates the use of optimized, efficient codes. CFD models must also address transition to turbulence in the boundary layer of rotors and airfoils, roughness effects, provide analyses of wake effects and effectively model flow compressibility. In the final stages of re-design and blade optimization engineers must be equipped with CFD tools capable of predicting noise performance. The global aspects of wind farm layout must also be carefully considered via analysis of large-scale, environmentally impacted flow fields in both land and offshore environment.
To address the above challenges the wind energy community needs rigorous CFD models that have been validated with quality experimental measurements. Only with such proven computational tools can a valuable insight into flow physics be achieved.