Improving the H-Darrieus rotor is often followed by the investigation of the influence of the turbine’s parameter design, notably, the aspect ratio, the solidity (σ), the tip speed ratio, and the airfoil profile shape. In this work, we are interested in both the aerodynamic flows around a straight cambered blade profile and the rotor turbine wake separation of a Darrieus vertical axis wind turbine. The aim of this study is to better understand the evolution of the instantaneous torque and the generated-separated blade vortex during full rotation. Indeed, a three-dimensional computational fluid dynamics model of a vertical axis wind turbine with a straight cambered blade profile NACA4312 operating over a large range of tip speed ratio is considered. The flows are governed by Reynolds-averaged Navier–Stokes equations and the turbulence is modeled with shear stress transport formulations k-ω. This research revealed a high correlation between the evolution of the torque coefficient and the generated-separated blades vortex. In particular, a good correlation between the maximum tip vortices size and the torque coefficient peak is demonstrated.

The cyclic variations of the Angle of Attack (AoA) during the operation of H-Darrieus VAWT bring them to operate under fatigue-type loads which stakes the blade’s endurance and the lifetime of the wind turbines. At low wind speed, the AoA exceeds the stall angle and causes significant variations in aerodynamic loads on the blades. This behavior is considered one of the most recognized weaknesses of VAWT technology. To mitigate these cyclic variations, one of the approaches adopted is to prescribe either a fixed or dynamic control pitching angle to the rotor blades that prevent them from having too large AoAs. This research aims to investigate the effect of several dynamic pitch angle strategies on the aerodynamic behavior of the H-Darrieus rotor. Four pitch control strategies were pursued to explore the effect of the pitch angle on the H-Darrieus performance and the angle of attack. A novel modified pitch control strategy has been adopted to monitor the rate of change of blade direction that is relative to the incoming wind flow. Insight was devoted to investigating the impact of this parameter on the performance and self-starting capabilities of the H-Darrieus rotor, at optimum and low wind speed. 3D unsteady lifting line free vortex wake-based model was performed. The results revealed two ranges of values for the setting parameter for which the produced torque followed an increasing and decreasing trend and which is still higher than the non-pitched blades. Furthermore, at the optimal TSR, dynamic pitching control showed no significant effect on the VAWT performance, as less than 3% was achieved. At low TSR, the torque increased almost six times as compared to the fixed and zero-pitched blades.

H-Darrieus vertical-axis wind turbines (VAWTs) capture wind regardless of its direction and operate effectively even in challenging and turbulent wind conditions. As a result, the blades operate under erratic and intricate aerodynamic loads, which cause them to bend. The performance of the H-Darrieus rotor will therefore be impacted by the blade’s deflection. This study aims at investigating the dynamic aerostructure influence on a novel convex-bladed H-Darrieus geometry. The results are compared to a straight-bladed baseline rotor. To do so, a two-way fluid–structure interaction (FSI)-coupled approach is performed to accurately address this issue. This approach allows for the simultaneous resolution of the fluid flow around the rotor and the mechanical structure responses inside the blades. The turbulent flows are resolved using the k-ω-SST model together with the URANS equations through computational fluid dynamics (CFD), while the structural deflections of the blades are assessed using finite element analysis (FEA). The results show that the performance of both H-Darrieus turbines decreases with increasing deformation. In addition, the study found that the carbon fiber composite (M1) material has the least deformation in the convex and straight blades, with values of 9.1 mm and 20.331 mm, respectively. The glass-fiber-reinforced epoxy composite (M3) material shows the most significant deflection across both types, with displacements of 32.50 mm and 73.78 mm for the straight blade and 19.02 mm and 43.03 mm for the convex blade. This study also reveals that the straight blade has a peak displacement of 73.785 mm when using the M3 material at TSR = 3, while the convex blade has a minimum displacement of 20.331 mm when using the M1 material, highlighting the varying performance characteristics of the materials. The maximum stress observed occurs in the straight blade, registering at 324.1 MPa with TSR = 3, which aligns closely with the peak displacement values, particularly for the aluminum alloy material (M2). In contrast, the convex blade made from the first material (M1) exhibits the lowest stress levels among the tested configurations.

Wind turbines are recently regarded as an alternative source of green energy. The challenge is to achieve the optimum design parameters and configurations, which provides the maximum power performance. Several researches have investigated the influence of the geometrical and operating turbine parameters. In this study, ANSYS FLUENT Computational Fluid Dynamics (CFD) software is used to study the aerodynamic flow around turbine blades. The aim of this paper is to give a deep insight into complex flow fields, tip vortices generation and dynamic stalls around turbine blades. 3D model of Vertical Axis Wind Turbine (VAWT) with straight cambered blade profile NACA 4312 operating at moderate specific TSR is investigated. An unsteady turbulent fluid flow based on the RANS equations and shear stress transport formulations SST.k-ω were adopted. This study reveals a great correlation between the evolution of the torque coefficient and the blade vortices generation. It has been shown that the maximum tip vortices size is closely correlated to the moment coefficient peak. In addition, the positive sloped curve on the moment coefficient is caused by the growing trend of vortices size along the blade.