Abstract: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-separa… Show more
“…Some works relate these detachments, the vortex generation, with the values of C P the rotor power coefficient for different angles. Qamar and Janajreh (2017) and Souaissa et al (2019) model Darrieus using CFD and although the behavior differs in some aspects, it is corroborated that the minimum values of C P corresponds to the highest vortex shedding zone. Bianchini et al (2017) also shows CFD results and comparisons with wake experiments for a three-bladed Darrieus rotor.…”
In this work, two-dimensional models of Savonius rotors are simulated using OpenFOAM® in order to predict the aerodynamic performance of small-scale vertical-axis wind turbines. The results are reported analyzing the aerodynamic performance and forces acting on the rotors. Power coefficient, [Formula: see text], is compared with experimental data for each operation point, and for three different geometries. Simulations with first- and second-order discretization schemes are carried out and compared, both quantitative and qualitative. Since usual grid dimensions result not to be suitable for simulations of Savonius rotors, an analysis of different domains is performed and compared. Finally, a set up for computational fluid dynamics simulation of two-dimensional Savonius rotors is proposed. The fluid–rotor interaction is analyzed and the vortex shedding is correlated with [Formula: see text] values and wake description.
“…Some works relate these detachments, the vortex generation, with the values of C P the rotor power coefficient for different angles. Qamar and Janajreh (2017) and Souaissa et al (2019) model Darrieus using CFD and although the behavior differs in some aspects, it is corroborated that the minimum values of C P corresponds to the highest vortex shedding zone. Bianchini et al (2017) also shows CFD results and comparisons with wake experiments for a three-bladed Darrieus rotor.…”
In this work, two-dimensional models of Savonius rotors are simulated using OpenFOAM® in order to predict the aerodynamic performance of small-scale vertical-axis wind turbines. The results are reported analyzing the aerodynamic performance and forces acting on the rotors. Power coefficient, [Formula: see text], is compared with experimental data for each operation point, and for three different geometries. Simulations with first- and second-order discretization schemes are carried out and compared, both quantitative and qualitative. Since usual grid dimensions result not to be suitable for simulations of Savonius rotors, an analysis of different domains is performed and compared. Finally, a set up for computational fluid dynamics simulation of two-dimensional Savonius rotors is proposed. The fluid–rotor interaction is analyzed and the vortex shedding is correlated with [Formula: see text] values and wake description.
“…This behavior is particularly relied upon by the use of a cambered airfoil profile. 31 Thus, in these regions, resistive torque has been generated that prevents the rotor from starting.Figure 9.Total torque coefficient at different operating TSRs: (a) instantaneous, (b) average.…”
Section: Resultsmentioning
confidence: 99%
“…The blades are profiled with a cambered airfoil NACA4312 that allows better self-starting capabilities. 26 The main geometrical features of the H-Darrieus are reported in Table 1.…”
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.
“…Mendoza et al [19] compared the wake of HAWTs and VAWTs in the atmospheric boundary layer with different surface roughness of terrain. Souaissa et al [20] focused on flows around a cambered blade profile and confirmed that the instantaneous torque is highly related to generated-separated blade vortex. Some innovative designs of VAWTs have been proposed in previous literature, and flow fields of these novel designs have been studied, too.…”
Currently, vertical axis wind turbines (VAWT) are considered as an alternative technology to horizontal axis wind turbines in specific wind conditions, such as offshore farms. However, complex unsteady wake structures of VAWTs exert a significant influence on performance of wind turbines and wind farms. In the present study, instantaneous flow fields around and downstream of an innovative VAWT with inclined pitch axes are simulated by an actuator line model. Unsteady flow characteristics around the wind turbine with variations of azimuthal angles are discussed. Several fluid parameters are then evaluated on horizontal and vertical planes under conditions of various fold angles and incline angles. Results show that the total estimated wind energy in the shadow of the wind turbine with an incline angle of 30° and 150° is 4.6% higher than that with an incline angle of 90°. In this way, appropriate arrangements of wind turbines with various incline angles have the potential to obtain more power output in a wind farm.
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