m. n. hamlaoui

The aerodynamic performance of wind turbines is significantly influenced by the design of their blades, which are engineered with advanced aerodynamic airfoils. However, the effectiveness of these designs is compromised by environmental factors such as dust, corrosion, sand, and insects, leading to alterations in blade shape and surface integrity over the turbine's operational period. These changes reduce the aerodynamic efficiency of the turbines. To assess these detrimental effects, this study utilizes a 3D Computational Fluid Dynamics (CFD) model based on the exact blade geometry. A modified version of the universal logarithmic wall function was implemented to quantify the influence of surface roughness. Comparative analyses between clean and rough blade surfaces under varying wind conditions showed that surface degradation significantly impacts the efficiency of wind turbines. Specifically, the findings indicate that surface roughness can lead to a substantial decrease in power output, with losses potentially reaching up to 35% under tested conditions. Notably, this roughness effect exhibits a critical value of  , beyond which the impact of roughness becomes negligible. Based on these results, an exponential correlation has been proposed. This study suggests that maintaining smooth blade surfaces or minimizing roughness is crucial for optimal turbine performance, especially under high wind conditions.

Accurate predictions of aerodynamic performance and near wake expansion around Horizontal Axis Wind Turbine (HAWT) rotors is pivotal for studying wind turbine wake interactions and optimizing wind farm layouts. This study introduces a novel engineering model centered on stall delay correction to enhance the precision of the Actuator Disk Method (ADM) predictions in both aerodynamic performance and near wake expansion around HAWT rotors. The model is developed based on a comprehensive study of the 3D lift coefficient evolution over the rotor blade, incorporating a shift parameter that considers both stall angle detection and radial decrement. The proposed approach demonstrates remarkable agreements, showcasing discrepancies as low as 7% for both loads and axial wake predictions. These quantifiable results underscore the effectiveness of the model in capturing intricate aerodynamic phenomena. Looking forward, the success of this approach opens avenues for broader applications, guiding future research in wind energy towards improved simulation accuracy and optimized wind farm designs.

The Actuator Disk Method (ADM), in its analytical formulation or combined with Navier-Stokes equations, is widely used for design and/or for aerodynamic analysis of Horizontal Axis Wind Turbines (HAWT). This method has demonstrated its capabilities for performance predictions of HAWT rotors for limited range of wind speeds with lower angles of attack values, i.e. attached flow conditions. However, for typical wind speeds that rotor encounters, under higher angles of attack i.e. stall conditions, such a method cannot describe accurately the flow characteristics around rotor-blades due to severe flow separations coupled with the effects of blades rotation as well as the radial flow over the blades. In this paper, original correction approaches have been proposed for the existing stall delay models to take into account both the blade rotation and the radial flow effects over the rotor blades. For this purpose, the ADM combined with 3D- NavierStokes equations formulation using Large Eddy Simulations (LES) model has been considered to describe the incompressible turbulent flow field around HAWT rotor blades. The resulting mathematical model has been solved using a 3D in-house subroutine developed with OpenFOAM code. The proposed numerical method has been validated against the well recognized reference measurements obtained using the New MEXICO and the NREL Phase VI experimental wind turbines. In comparison with existing stall delay models, the proposed correctionapproaches, especially the radial flow approach, have shown noticeable enhancements on performance predictions of HAWT rotors compared to the experimental measurements. It has been found very low discrepancies to the experimental torque and thrust values, up to 1% and 10% have been recorded respectively.