Search Results (46)

The intentional yaw offset of wind turbines has shown potential to redirect wakes, enhancing overall plant power production, but it may increase fatigue loading on turbine components. This study analyzed fatigue loads on the NREL 5 MW reference wind turbine under varying yaw offsets using blade element momentum theory, dynamic blade element momentum, and the converging Lagrange filaments vortex method, all implemented in OpenFAST. Simulations employed yaw angles from −40° to 40°, with turbulent inflow generated by TurbSim, an OpenFAST tool for realistic wind conditions. Fatigue loads were calculated according to IEC 61400-1 design load case 1.2 standards, using thirty simulations per yaw angle across five wind speed bins. Damage equivalent load was evaluated via rainflow counting, Miner’s rule, and Goodman correction. Results showed that the free vortex method, by modeling unsteady aerodynamic forces, yielded distinct differences in damage equivalent load compared to the blade element method in yawed conditions. The free vortex method predicted lower damage equivalent load for the low-speed shaft bending moment at negative yaw offsets, attributed to its improved handling of unsteady effects that reduce load variations. Conversely, for yaw offsets above 20°, the free vortex method indicated higher damage equivalent for low-speed shaft torque, reflecting its accurate capture of dynamic inflow and unsteady loading. These findings highlight the critical role of unsteady aerodynamics in fatigue load predictions and demonstrate the free vortex method’s value within OpenFAST for realistic damage equivalent load estimates in yawed turbines. The results emphasize the need to incorporate unsteady aerodynamic models like the free vortex method to accurately assess yaw offset impacts on wind turbine component fatigue. Full article

For unmanned aerial vehicles with long-duration autonomous missions, efficient energy management is critically important. One of the most promising solutions is solar power, the implementation of which requires the continuous orientation tracking of the Sun’s position. This study presents a three-axis active solar tracking system based on a gimbal mount, providing full kinematic control of the panel in space. A mathematical model of orientation is developed using the Earth-Centered Inertial, local geographic frame, and unmanned aerial vehicle body coordinate systems. An aerodynamic analysis is conducted, including a quantitative assessment of drag, lift, and torque on the panel. Based on the obtained characteristics, limiting conditions for the safe operation of the tracker are formulated. An adaptive control algorithm is introduced, minimizing a generalized objective function that accounts for angular deviation, aerodynamic loads, and current energy balance. Numerical simulations are described, demonstrating system stability under various scenarios: turbulence, maneuvers, power limitations, and sensor errors. The results confirm the effectiveness of the proposed approach under real-world operating conditions. Full article

With the increasing capacity of wind turbines, key components including the rotor diameter, tower height, and tower radius expand correspondingly. This heightened inertia extends the response time of pitch actuators during rapid wind speed variations occurring above the rated wind speed. Consequently, wind turbines encounter significant output power oscillations and complex structural loading challenges. To address these issues, this paper proposes a novel pitch control strategy combining an effective wind speed estimation with the inverse system method. The developed control system aims to stabilize the power output and rotational speed despite wind speed fluctuations. Central to this approach is the estimation of the aerodynamic rotor torque using an extended Kalman filter (EKF) applied to the drive train model. The estimated torque is then utilized to compute the effective wind speed at the rotor plane via a differential method. Leveraging this wind speed estimate, the inverse system technique transforms the nonlinear wind turbine dynamics into a linearized, decoupled pseudo-linear system. This linearization facilitates the design of a more agile pitch controller. Simulation outcomes demonstrate that the proposed strategy markedly enhances the pitch response speed, diminishes output power oscillations, and alleviates structural loads, notably at the tower base. These improvements bolster operational safety and stability under the above-rated wind speed conditions. Full article

This study presents the development of an adaptive control system for aerodynamic flaps of a two-tier vertical-axis Savonius wind rotor to improve performance under variable wind loads. The approach includes detailed kinematic and dynamic modeling of the flap actuation mechanism, accounting for real-world nonlinearities such as backlash, friction, and impact loads. The mechanical transmission system is analyzed to evaluate the influence of design parameters on system dynamics and control accuracy. A mathematical model of an adaptive PID controller is proposed, capable of real-time adjustment of gain parameters based on external wind torque. Numerical simulations under various wind conditions demonstrate that adaptive tuning significantly enhances system stability, reduces overshoot, and ensures faster response compared to fixed-parameter controllers. Sensitivity analysis confirms the importance of mass distribution, mechanical stiffness, and damping in minimizing vibrations and ensuring durability. The developed system provides a reliable solution for efficient wind energy conversion in dynamic environments, including urban and coastal applications. Full article

This paper presents an experimental and numerical investigation of a 254 mm resin-printed propeller operating at rotational speeds between 3000 and 9000 RPM. Propeller thrust and torque were measured using a six-degree-of-freedom load cell, while acoustic data were captured with a microphone positioned three times the propeller diameter from the center. To complement the experimental analysis, computational simulations were conducted using ANSYS Fluent with the detached eddy simulation (DES) model, the Ffowcs-Williams and Hawkings (FW-H) model, and a transient flow solver. The figure of merit (FM) results show that the resin propeller slightly outperforms two commercial counterparts with a marginal difference between the wood and resin propellers. Additionally, the resin propeller demonstrates better noise performance, exhibiting the lowest primary tonal noise, broadband noise, and overall sound pressure level (OASPL), with minimal differences between the two commercial counterparts. ANSYS Fluent simulations predict thrust and torque within a 10% error margin, showing particularly accurate results for primary tonal noise. A new trade-off index is proposed to assess the balance between propeller performance and aeroacoustics, revealing distinct trends compared to traditional metrics. Furthermore, aerodynamic phenomena such as flow separation on the leading edge near the tip, flow separation behind the middle trailing edge, and vortex interactions at the root are identified as key contributors to tonal and broadband noise. These findings provide valuable insights into propeller design and aeroacoustic optimization. Full article

This study details the design and testing of a custom test rig for evaluating the performance of both open and shrouded rotors. The rig includes a two-axis load cell that is directly connected to the rotor to measure the rotor thrust separated from the total thrust when testing shrouded rotors and ensure accurate torque measurements, independent of external structural influences. Moreover, a main load cell is used to measure the total thrust for both configurations (open and shrouded rotor), as it is connected to the entire setup. Rotor RPM is monitored by capturing the voltage frequency from the BLDC motor, controlled using a Pololu Maestro Controller through the electronic speed controller. A shunt resistance is used to calculate the current through the electric Brushless Direct Current (BLDC) motor and by measuring the voltage, the electric power is calculated. By combining both mechanical and electrical power measurements, the BLDC motor’s efficiency is calculated. Automated data collection is conducted using National Instruments DAQ systems, with averaged measurements of thrust, torque, RPM, current, and voltage. Two rotors are tested to obtain performance data for both open and shrouded configurations. Additionally, a computational study is carried out to account for the aerodynamic effects of the rig’s structural elements. Uncertainty analysis is employed to assess the reliability of the experimental results by quantifying the numerical errors associated with both random and systematic errors encountered during the rotor’s performance evaluation. Full article

Wind turbine design is an iterative process. Many aspects are considered when designing a wind turbine, including aerodynamic and power performance, structural loads and behavior, and control techniques. In the preliminary design stages, the governing equations of each design aspect are used to calculate the different loads and performance outputs while optimizing between them. This is usually made using wind turbine simulation software. This work presents a data-based machine learning (ML) approach towards the design of a micro-scale wind turbine. Extensive simulations are made on a 45 cm diameter rotor while performing parametric analysis using the QBlade wind turbine simulation tool. Different design parameters and wind conditions were changed one at a time, and data were collected to be further analyzed and used to train the ML models. The measurable outputs of the models are the coefficient of power (C_P), loads normal and tangential to the blade at midspan (F_N and F_T), and the torque (T) on the rotor. Linear regression was found unsuitable for predicting C_P due to its high nonlinearity; however, it gave satisfactory results for the blade loads. Ensemble models were found to give the highest accuracy for predicting all the desired outputs. The model accuracy is measured in terms of the coefficient of determination (R²), where the model could predict C_p, F_N, F_T, and T with R² values of 0.999, 0.984, 0.984, and 0.986 respectively. Full article

This study aims to introduce a new optimization method for designing a vertical-axis wind turbine (VAWT) that dynamically morphs its blades as a function of the tip-speed ratio (TSR) and azimuthal angle. For this purpose, the Darrieus turbine is the subject of a dynamic study under transient aerodynamic loads. By resolving the two-dimensional unsteady incompressible Navier–Stokes equation, the aerodynamic torque is obtained with the k-$ϵ$ realizable turbulence model. A comparison between rotor operation at optimal and lower  ${\mathrm{C}}_p$ values is possible according to the investigation of flow-field characteristics for a variety of tip-speed ratio values, with experimental results so that a better understanding of the vertical-axis wind turbine’s basic physics is obtained. Then, a multi-objective optimization technique is coupled with ANSYS Workbench to increase the energy generation of VAWT blades by reducing the drag coefficient and maximizing the power coefficient. The input variables were evaluated through a sensitivity analysis, and the most important one was chosen. The analysis results of the best compromise showed that the design methodology’s output is feasible for manufacturing. Full article

Multi-rotor system (MRS) wind turbines can provide a competitive alternative to large-scale wind turbines due to their significant advantages in reducing capital, transportation, and operating costs. The main challenges of MRS wind turbines include the complexity of the supporting structure, mathematical modeling of the aerodynamic interaction between the rotors, and the yaw control mechanism. In this work, MATLAB 2018b/Simulink^® software was used to model and simulate a twin-rotor wind turbine (TRWT), and an NREL 5 MW wind turbine was used to verify the model outputs. Different random signals of wind velocities and directions were used as inputs to each rotor to generate different thrust loads, inducing twisting moments on the main tower. A yaw controller system was adapted to ensure that the turbine constantly faced the wind to maximize the power output. A DC motor was used as the mechanism’s actuator. The goal was to achieve a compromise between aligning the rotors with the wind direction and reducing the torque induced on the main tower. A comparison between linear and nonlinear controllers was performed to test the yaw system actuator’s response at different wind speeds and directions. Sliding mode control (SMC) was chosen, as it was suitable for the nonlinearity of the system, and its performance showed a faster response compared with the PID controller, with a settling time of 0.17 sec and a very low overshoot. The controller used the transfer function of the motor to generate a sliding surface. The dynamic responses of the controlled angle are shown and discussed. The controller showed promising results, with a suitable response and low chattering signals. Full article

Besides improving the generator torque and blade pitch controller, incorporating additional control actuations, such as a vibration absorber and active ballast, into the floating offshore wind turbine (FOWT) system is also promising for the motion mitigation of FOWTs. This work aims to study the catenary mooring length re-configuration effect on the dynamic behaviours of semi-submersible FOWTs. The mooring length re-configuration mentioned here is achieved by altering the mooring length with winches mounted on the floating platform, which is in a period of minutes to hours, so that the mooring tensions could be adjusted to reduce the aerodynamic load induced platform mean pitch. Control designs for both single mooring line and multiple mooring lines have been described and studied comparatively. In order to assess the motion mitigation performance of the proposed mooring line length re-configuration methods, fully coupled numerical simulations under different environmental cases have been conducted. Results indicate that the catenary mooring length re-configuration is able to reduce the platform pitch motion by up to 15.8% under rated condition, while careful attention must be paid to the scenarios where the catenary moorings become taut, which may lead to large load variations. Full article

UAV rotors are at a high risk of ice accumulation during their operations in icing conditions. Thermal ice protection systems (IPSs) are being employed as a means of protecting rotor blades from ice, yet designing the appropriate IPS with the required heating density remains a challenge. In this work, a reduced-order modeling technique based on the Unsteady Vortex Lattice Method (UVLM) is proposed as a way to predicting rotor icing and to calculate the required anti-icing heat loads. The UVLM is gaining recent popularity for aircraft and rotor modeling. This method is flexible enough to model difficult aerodynamic problems, computationally efficient compared to higher-order CFD methods and accurate enough for conceptual design problems. A previously developed implementation of the UVLM for 3D rotor aerodynamic modeling is extended to incorporate a simplified steady-state icing thermodynamic model on the stagnation line of the blade. A viscous coupling algorithm based on a modified α-method incorporates viscous data into the originally inviscid calculations of the UVLM. The algorithm also predicts the effective angle of attack at each blade radial station (r/R), which is, in turn, used to calculate the convective heat transfer for each r/R using a CFD-based correlation for airfoils. The droplet collection efficiency at the stagnation line is calculated using a popular correlation from the literature. The icing mass and heat transfer balance includes terms for evaporation, sublimation, radiation, convection, water impingement, kinetic heating, and aerodynamic heating, as well as an anti-icing heat flux. The proposed UVLM-icing coupling technique is tested by replicating the experimental results for ice accretion and anti-icing of the 4-blade rotor of the APT70 drone. Aerodynamic predictions of the UVLM for the Figure of Merit, thrust, and torque coefficients agree within 10% of the experimental measurements. For icing conditions at −5 °C, the proposed approach overestimates the required anti-icing flux by around 50%, although it sufficiently predicts the effect of aerodynamic heating on the lack of ice formation near the blade tips. At −12 °C, visualizations of ice formation at different anti-icing heating powers agree well with UVLM predictions. However, a large discrepancy was found when predicting the required anti-icing heat load. Discrepancies between the numerical and experimental data are largely owed to the unaccounted transient and 3D effects related to the icing process on the rotating blades, which have been planned for in future work. Full article

Limited by scaling effects, the physical model tests of FOWTs (floating offshore wind turbines) cannot simulate the aerodynamic loads on rotors correctly. To solve this problem, the real-time hybrid model tests in wind tunnels were developed and provided a feasible solution for the aerodynamic simulation. To perform the wind tunnel tests, the design of aerodynamic equivalent rotor models is most critical. In this study, an innovative methodology of aerodynamic equivalent design for the wind turbine rotors is developed based on GA (genetic algorithm). The NREL (National Renewable Energy Laboratory) 5 MW and DTU (Technical University of Denmark) 10 MW rotors are employed for the case studies to validate the proposed methodology. According to the results, the model-scale aerodynamic thrust performance can be accurately matched with the prototype in the entire region between cut-in and cut-out wind speeds, which allows the rotor model to provide correct thrust at different wind speeds. The variance of the aerodynamic torque with the wind speeds for the developed model is also in good agreement with the prototype, which could be beneficial for the design of the model-scale active pitch control strategy. Moreover, the applicability of the fitness functions of GA is discussed. Full article

Switched reluctance motors (SRMs) face challenges in achieving high performances in terms of the power factor, torque per ampere, and torque ripples. Although several parameters impact their performance, magnetic saliency has a significant impact. This paper presents a study on the influence of the saliency ratio on the performance of switched reluctance motors. A detailed design procedure for a mid-drive electric motor for a high-performance electric bike is presented. A systematic methodology is adopted to estimate the power rating for desired vehicle performance while considering the vehicle’s mechanical and aerodynamic parameters. Additionally, the paper discusses and analyzes the design of two SRM motor configurations with different rotor poles (6/4 and 6/10) while performing magnetostatic analysis for generated torque validation. A parametric study is performed on the 6/10 SRM design for further improvement in the torque profile while keeping the same fill factor and electrical loading. Furthermore, the transient analysis in Ansys Maxwell 2D for both SRMs confirms the designed performance. The results shows that the SRM with higher rotor poles (6/10) is a better choice. Full article

A key challenge in flapping-wing micro air vehicle (FWMAV) design is to generate high aerodynamic force/torque for improving the vehicle’s maneuverability. This paper presents a bio-inspired hover-capable flapping-wing micro air vehicle, named RoboFly.S, using a cross-tail wing to adjust attitude. We propose a novel flapping mechanism composed of a two-stage linkage mechanism, which has a large flapping angle and high reliability. Combined with the experimentally optimized wings, this flapping mechanism can generate more than 34 g of lift with a total wingspan of 16.5 cm, which is obviously superior to other FWMAVs of the same size. Aerodynamic force/torque measurement systems are used to observe and measure the flapping wing and aerodynamic data of the vehicle. RoboFly.S realizes attitude control utilizing the deflection of the cross-tail wing. Through the design and experiments with tail wing parameters, it is proved that this control method can generate a pitch torque of 2.2 N·mm and a roll torque of 3.55 N·mm with no loss of lift. Flight tests show that the endurance of RoboFly.S can reach more than 2.5 min without interferences. Moreover, the vehicle can carry a load of 3.4 g for flight, which demonstrates its ability to carry sensors for carrying out tasks. Full article

An investigation of twin corotating rotors’ interaction effects was performed by load (thrust and torque) measurements, flow field dynamics through Time-Resolved Particle Image Velocimetry, and acoustic emissions using a microphone array. Two rotors, each with a diameter of D = 393.7 mm and equipped with three blades, were investigated in a side-by-side configuration, to simulate a multirotor propulsion system. The mutual distance between the propellers is 1.02 D, and four different rotating speeds, i.e., 2620, 3500, 4360, and 5200 RPM, were explored. In such a configuration, thrust and torque undergo a reduction compared to that found for a single propeller configuration. The level of aerodynamic load fluctuations increases as well. The interaction of the wakes produces a recirculation region at the external periphery of the shear layers. An innovative approach involving the coupling of Proper Orthogonal Decomposition (POD) and Wavelet Transform has been employed to investigate the dominant structures within the flow and their mutual influence. The results reveal that the interacting wakes are dominated by a wave-like motion pulsating at Harmonics of the Blade Passing Frequency (HBPF) of 1/3. Higher orders of POD modes capture coherent vortical structures, including tip vortices pulsating at HBPF = 1. The aeroacoustic investigation shows that the noise level, in terms of the Over All Sound Pressure Level, presents a remarkable increment concerning that generated by the single propeller. Full article