Search

To enable wind energy to surpass fossil fuels, the power-to-cost ratio of wind turbines must be competitive. Increasing installation capacities and wind turbine sizes indicates a strong trend toward clean energy. However, larger rotor diameters, reaching up to 170 m, introduce stability and aeroelasticity concerns and aerodynamic phenomena that cause noise disturbances. These issues hinder performance enhancement and social acceptance of wind turbines. A critical aerodynamic challenge is flow separation on the blade's suction side, leading to a loss of lift and increased drag, ultimately stalling the blade and reducing turbine performance. Various active and passive flow control techniques have been studied to address these issues, with passive techniques offering the advantage of no external energy requirement. High-lift devices, such as leading-edge slats, are promising in improving aerodynamic performance by controlling flow separation. This study explores the geometric parameters of slats and their effects on wind turbine blades' aerodynamic and acoustic performance. Using an adequate turbulence model at Re = 106 for angles of attack from 14° to 24°, 77 slat configurations were evaluated. Symmetric slats showed superior performance at high angles of attack, while slat chord length was inversely proportional to aerodynamic improvement. A hybrid method was employed to predict noise, revealing slat-induced modifications in eddy topology and increased low- and high-frequency noise. This study's main contribution is correlating slat-induced aerodynamic improvements with their acoustic effects. The directivity reveals a 10–15 dB reduction induced by the slat at 1 kHz, while the slat induces higher noise at higher frequencies. [ABSTRACT FROM AUTHOR]

Indoor air quality determines the comfort, health, and wellbeing of people in buildings. Windows are the optimal elements for providing natural ventilation and fresh air, but the outside contains suspended particles that can be harmful in high concentrations. This work presents an openable and double-glazed façade component with a cavity that includes a series of slats that filter the air and depurate it by means of a photocatalytic reaction (TiO2). This component integrates the functions of ventilation, solar protection, and air purification, which were analysed in the slat and the façade component to approve a preliminary design. To this end, it was applied to a specific case, a non-residential building at a latitude 41° N in a Mediterranean climate. The results show the optimal dimensions according to solar radiation and ventilation in this specific case and the method used to obtain them, along with the increase in the temperature of the incoming air with respect to the outside (10 °C). Finally, the results obtained from a photocatalytic coating sample show that the NOx degradation can be up to 9%. All these results confirm the applicability of this component in buildings and pave the way for further research. [ABSTRACT FROM AUTHOR]

To enable wind energy to surpass fossil fuels, the power-to-cost ratio of wind turbines must be competitive. Increasing installation capacities and wind turbine sizes indicates a strong trend toward clean energy. However, larger rotor diameters, reaching up to 170 m, introduce stability and aeroelasticity concerns and aerodynamic phenomena that cause noise disturbances. These issues hinder performance enhancement and social acceptance of wind turbines. A critical aerodynamic challenge is flow separation on the blade’s suction side, leading to a loss of lift and increased drag, ultimately stalling the blade and reducing turbine performance. Various active and passive flow control techniques have been studied to address these issues, with passive techniques offering the advantage of no external energy requirement. High-lift devices, such as leading-edge slats, are promising in improving aerodynamic performance by controlling flow separation. This study explores the geometric parameters of slats and their effects on wind turbine blades’ aerodynamic and acoustic performance. Using an adequate turbulence model at Re = 106 for angles of attack from 14° to 24°, 77 slat configurations were evaluated. Symmetric slats showed superior performance at high angles of attack, while slat chord length was inversely proportional to aerodynamic improvement. A hybrid method was employed to predict noise, revealing slat-induced modifications in eddy topology and increased low- and high-frequency noise. This study’s main contribution is correlating slat-induced aerodynamic improvements with their acoustic effects. The directivity reveals a 10–15 dB reduction induced by the slat at 1 kHz, while the slat induces higher noise at higher frequencies.

Indoor air quality determines the comfort, health, and wellbeing of people in buildings. Windows are the optimal elements for providing natural ventilation and fresh air, but the outside contains suspended particles that can be harmful in high concentrations. This work presents an openable and double-glazed façade component with a cavity that includes a series of slats that filter the air and depurate it by means of a photocatalytic reaction (TiO2). This component integrates the functions of ventilation, solar protection, and air purification, which were analysed in the slat and the façade component to approve a preliminary design. To this end, it was applied to a specific case, a non-residential building at a latitude 41° N in a Mediterranean climate. The results show the optimal dimensions according to solar radiation and ventilation in this specific case and the method used to obtain them, along with the increase in the temperature of the incoming air with respect to the outside (10 °C). Finally, the results obtained from a photocatalytic coating sample show that the NOx degradation can be up to 9%. All these results confirm the applicability of this component in buildings and pave the way for further research.

The potential of airfoil optimisation for the specific requirements of airborne wind energy (AWE) systems is investigated. Experimental and numerical investigations were conducted at high Reynolds numbers for the S1223 airfoil and an optimised airfoil with thin slat. The optimised geometry was generated using the NSGA-II optimisation algorithm in conjunction with 2D-RANS simulations. The results showed that simultaneous optimisation of the slat and airfoil is the most promising approach. Furthermore, the choice of turbulence model was found to be crucial, requiring appropriate transition modeling to reproduce experimental data. The k-ω-SST-γ-Reθ model proved to be most suitable for the geometries investigated. Wind tunnel experiments were conducted with high aspect ratio model airfoils, using a novel structural design, relying mostly on 3D-printed airfoil segments. The optimised airfoil and slat geometry showed significantly improved maximum lift and a shift of the maximum power factor to higher angles of attack, indicating good potential for use in AWE systems, especially at higher Reynolds numbers. The combined numerical and experimental approach proved to be very successful and the overall process a promising starting point for future optimisation and investigation of airfoils for AWE systems.

The potential of airfoil optimisation for the specific requirements of airborne wind energy (AWE) systems is investigated. Experimental and numerical investigations were conducted at high Reynolds numbers for the S1223 airfoil and an optimised airfoil with thin slat. The optimised geometry was generated using the NSGA-II optimisation algorithm in conjunction with 2D-RANS simulations. The results showed that simultaneous optimisation of the slat and airfoil is the most promising approach. Furthermore, the choice of turbulence model was found to be crucial, requiring appropriate transition modeling to reproduce experimental data. The k- ω - S S T - γ - R e θ model proved to be most suitable for the geometries investigated. Wind tunnel experiments were conducted with high aspect ratio model airfoils, using a novel structural design, relying mostly on 3D-printed airfoil segments. The optimised airfoil and slat geometry showed significantly improved maximum lift and a shift of the maximum power factor to higher angles of attack, indicating good potential for use in AWE systems, especially at higher Reynolds numbers. The combined numerical and experimental approach proved to be very successful and the overall process a promising starting point for future optimisation and investigation of airfoils for AWE systems. [ABSTRACT FROM AUTHOR]

The flow around the slat cove of a two-dimensional 30P30N multi-element airfoil is investigated with time-resolved particle image velocimetry (TR-PIV) at low Reynolds number (Rec = 2.41 × 104 and 4.61 × 104). The effects of angle of attack (α = 8°, 12°, and 16°) on the mean flow characteristics and vortex dynamics are discussed. The size of the recirculation within the slat cove and the intensity of the shed vortices originating from the slat cusp shear layer are found to generally decrease as the angle of attack increases. The joint time-frequency analyses show that disturbances of different frequencies exist in the slat cusp shear layer and they trigger the different vortex shedding patterns of the slat cusp shear layer. The self-sustained oscillation within the slat cove, normally observed at high Reynolds number (Rec ~ 106), is proved to be responsible for the disturbances of different frequencies and the related vortex dynamics in the current study. [ABSTRACT FROM AUTHOR]

Recently, there have been significant developments in the field of vibration energy harvesters to feed sensors for structural health monitoring in aeronautics and other high technology fields. Within the framework of the EU InComEss project, new eco-friendly piezoelectric materials are under development. A foreseen application is vibration energy harvesting from the wing slats of aircraft. Semi-analytical models of the vibrating slat make it possible to estimate the maximum voltage that can be generated by a piezoelectric patch bonded to a slat surface. A more detailed analysis must consider details of the three-dimensional geometry of both the harvester and the bonding layer. This can only be carried out with multiphysics finite element software. A finite element model of a whole slat would require a large computational effort as millions of elements are typically needed to model very thin piezoelectric layers. To simplify this analysis, an integrated analytical–numerical method is proposed in this paper. A large-scale analytical model of the whole slat was used to calculate loads on the portion of the slat where a piezoelectric patch was attached. Then, a small-scale finite element model of the portion of the slat with the piezoelectric patch was used to calculate the open circuit voltage generated by the patch. The response of the harvester to random excitation, typical of aeronautic applications, was calculated. The effects of the details of the harvester design on the generated voltage were analyzed and discussed. [ABSTRACT FROM AUTHOR]

The present study considers the use of a slat near the leading edge of an airfoil to delay or completely cancel separation and thus improves the performance of small wind turbines, in addition to lowering the cost of the blade by reducing the used material. Flow around the S809 airfoil with a slat is numerically simulated using ANSYS 2019 R1 (CFD) program. The present work concentrates on two geometrical parameters namely the location of the slat relative to the base airfoil and the chord size of the slat. Relative to the total chord length of the main airfoil, a slat with a chord length 10% is located at range of distances +3.6% to +10.8% in y direction, slat located at 9% shows the best lift coefficient. To study the effect of slat size, slat sizes range from 5% to 12.5% are numerically investigated, slat size 7.5% shows the best lift coefficient and attached flow over the airfoil for a wide range of angles of attack. The improvement is achieved with the same total chord length with 12% saving of material which corresponds to 6% of the total cost of the turbine. • Improving the aerodynamic performance of the airfoil using leading edge slat. • ANSYS FLUENT is used to simulate the flow around the S809 airfoil with a slat. • The size and location of the leading-edge slat are investigated. • The proposed slat design reduced the material used in wind turbine blades by 12%. • The lift coefficient increased by 24.89% for the best slat design. [ABSTRACT FROM AUTHOR]