Search Results (97)

During the worldwide energy transition, wind power has become a leading development direction. Compared to large-scale horizontal-axis wind turbines (HAWTs), small-scale vertical-axis wind turbines (VAWTs) show potential, lack yaw mechanisms, adapt to wind direction changes, and are cost-effective. However, small-scale VAWTs operate in the near-surface atmospheric boundary layer and are sensitive to low-temperature and high-humidity climates, which cause blade icing. Ice buildup leads to fluctuations in aerodynamic loads, reduces power output, and diminishes stability. This study focuses on the NACA-0018 airfoil, using a low-temperature wind tunnel platform to simulate freezing durations to obtain ice characteristics on the blade surface. Based on ice profiles, numerical models were developed. Computational fluid dynamics (CFD) techniques were used to perform unsteady simulations of aerodynamic performance at various icing durations, investigating the influence on the power coefficient. The results indicate that the effect of icing duration on the average power coefficient depends on TSR. At the 5 min icing stage, the optimal tip-speed ratio decreases. Icing deteriorates aerodynamic performance at high tip-speed ratios, while producing positive optimization effects at low tip-speed ratios. This paper reveals the variation patterns of aerodynamic performance and differentiated mechanisms during the icing process of small vertical-axis wind turbine blades, providing a theoretical basis and data support for the development of surface anti-icing technologies and safe, efficient operation in low-temperature environments. Full article

The cloud spatial uniformity in the test section is crucial for icing wind tunnels in aircraft icing research and airworthiness certification. To achieve uniform supercooled large droplet (SLD) icing conditions, both the spatial variation in droplet size distribution and the concentration should be considered. In this study, the spatial distribution of droplets under three SLD conditions is explored in the Aviation Industry Corporation of China Aerodynamics Research Institute (AVICARI)’s FL-61 icing wind tunnel. Measurements are conducted at 12 test points in vertical and horizontal directions using the holographic airborne cloud particle imager (HACPI) in conjunction with a two-axis traversing system. The droplet images obtained at specific test points below the test section centerline show deformation phenomena for droplets larger than 400 $\mathsf{\mu }$m. Additionally, the aspect ratio of deformed droplets increases with droplet size. The spatial evolution of the median volume diameter (MVD) and liquid water content (LWC) is examined. For two spray arrangements where the activated nozzles are positioned close, the test point where the LWC peak in the vertical direction occurs is higher than that of the MVD peak. Further analysis focuses on the size distribution of droplets in the vertical direction. The results show that the settling effect of the droplets larger than 50 $\mathsf{\mu }$m is evident under a flow velocity of 78 m/s. Meanwhile, the position where large droplets tend to appear lowers as the droplet size increases. Finally, the spatial uniformity of droplet size distributions at the same radial distance is discussed. Full article

Ice accretion is a significant threat to the operation of UAVs in cold climates. This study analyzed the performance degradation caused by ice accretion on a propeller with a diameter of 0.53 m for a small UAV in an icing wind tunnel. Three different droplet diameters of 20, 40, and 60 µm were tested along with three liquid water contents between 0.28 g/m³ and 1.12 g/m³ along with temperatures of −5 °C, −10 °C, and −15 °C. Additionally, the influence of the variation in the rotation rate was measured. The droplet diameter was observed to have the strongest influence on the propeller’s performance. An increase in the median volume diameter from 20 µm to 40 µm was correlated with a significant decrease in the propeller’s performance. After a minute of icing, the experiment at 20 µm showed a reduction in thrust of 25% compared to a decrease in thrust by 100% for the 40 µm case and 120% for the 60 µm case, meaning that the propeller is not generating thrust, but is generating drag. The temperature influences the propeller’s performance, with the most substantial performance degradation at −5 °C and a decrease in the performance impact with a temperature reduction. Analyzing the performance impact is an important step for deploying UAVs in icing conditions by detecting the most critical conditions for the performance of a UAV propeller. The analysis shows that the most critical conditions are at −5 °C and that an increase in droplet diameter and liquid water content leads to more severe icing conditions. The results show the need for future analysis comparing the performance impact of a propeller at different icing wind tunnels and the validation of numerical methods for predicting the performance degradation of a UAV propeller. Full article

Offshore wind turbine blades operating in cold climates are frequently affected by surface icing, which compromises aerodynamic performance and reduces power output. To address this challenge, the present study conducted controlled icing wind tunnel experiments to investigate how salinity and liquid water content (LWC) influence ice formation on the S809 airfoil surface. Results indicate that increased salinity substantially inhibits ice accretion: as salinity rises from 0‰ to 35‰, the total icing area rate drops by approximately 20.5% within 6 min, and the maximum ice thickness declines from 17.21 mm to 6.03 mm. Conversely, LWC emerges as a dominant factor intensifying icing severity: raising LWC from 0.5 g/m³ to 1.5 g/m³ leads to a 135% increase in icing area and an increase in maximum ice thickness from 7.69 mm to 18.17 mm. A notable synergistic interaction is observed—higher LWC enhances the inhibitory effect of salinity on ice formation. These findings offer valuable insights into the icing dynamics under marine atmospheric conditions and provide a theoretical foundation for the development of anti-icing strategies for offshore wind turbine blades. Full article

The requirements of the upcoming aircraft generation based on hybrid or electric propulsion discourage the use of Ice Protection Systems (IPSs) based on hot-air spilled from engine or demanding a large consumption of electrical power. In line with this need, a low-power IPS based on piezoelectric (PZT) technology is investigated in the current article. Its main objective is to protect an aerodynamic surface by removing ice accretions (de-icing). The idea at the basis of the concept is to drive mechanical waves at the interface between the skin and the ice layer to cause the breaking and the detachment. Moving from an assessed layout and numerical simulations providing the most effective design configuration, dedicated small-scale airfoil demonstrators (NACA 0012 with a chord of 310 mm and a span of 150 mm) were manufactured, with the aim of testing the technology within the representative environment of the IFAM Icing Wind Tunnel (IWT). The test results showed, for power consumption of 4.4 kW/m², ice detachment levels -based on the ice-covered area- between 40 and 50% at −10 °C, about 40% at −20 °C, and a maximum of 15% at −4 °C. The results highlighted the impact of some specific parameters (environmental temperature, skin, and ice thickness) on the effectiveness of the IPS. Full article

This paper presents the design, manufacturing, instrumentation and validation by tests (ground and icing wind tunnel) of a full-scale Hybrid Laminar Flow Control (HLFC) leading-edge demonstrator based on Airbus A330 outer wing plan-form. The Ground-Based Demonstrator (GBD) was developed to reproduce a full-scale, realistic wing section integrating into the leading-edge three key systems: micro-perforated skin for the hybrid laminar flow control suction system (HLFC), the hot-air Wing Ice Protection System (WIPS) and a folding “bull nose” Krueger high-lift device. The demonstrator combines a superplastic-formed and diffusion-bonded (SPF/DB) perforated titanium skin mounted on aluminum ribs jointed with a carbon-fiber-reinforced polymer (CFRP) wing box. Titanium internal ducts were designed to ensure uniform hot-air distribution and structural compatibility with composite components. Manufacturing employed advanced aeronautical processes and precision assembly under INCAS coordination. Ground tests were performed using a dedicated hot-air and vacuum rig delivering up to 200 °C and 1.6 bar, thermocouples and pressure sensors. The results confirmed uniform heating (±2 °C deviation) and stable operation of the WIPS without structural distortion. Relevant tests were performed in the CIRA Icing Wind Tunnel facility, verifying the anti-ice protection system and Krueger device. The successful design, fabrication, testing and validation of this multifunctional leading edge—featuring integrated HLFC, WIPS and Krueger systems—demonstrates the readiness of the concept for subsequent aerodynamic testing. Full article

Ice accretion on arctic vessels and offshore platforms poses serious threats to navigation and operational safety. Existing research has primarily focused on isolated structures. This study employs a combined approach of numerical simulation and experimental validation. It systematically investigates the icing characteristics of tandem twin-cylinders in wake flow fields. This configuration is common yet rarely studied in real marine environments. The model employs two identical cylinders arranged in tandem. It examines the effects of wind speed, distance, diameter, and wind direction angle on ice accretion morphology and distribution. Validation was conducted through wind tunnel tests at 5 m/s wind speed and 2.0 g/m³ liquid water content. Results demonstrate a significant shielding effect from the upstream cylinder wake. As wind speed increases, the ice mass difference between upstream and downstream cylinders widens. Ice mass shows a nonlinear relationship with distance. Minimum ice accretion on the downstream cylinder occurs at 350–450 mm distance. This results from wake pattern transition. The shielding effect exhibits strong nonlinear dependence on wind direction angle. A deviation of 8.2° increases total ice mass by 242.5%. Multivariable analysis confirms these nonlinear mechanisms persist under coupled distance–wind speed variations. This study provides the first systematic revelation of twin-cylinder icing mechanisms in wake flow fields. It offers a validated predictive tool for anti-icing design of arctic marine structures. Full article

As an efficient and clean renewable energy source, wind energy plays a crucial role in optimizing the energy structure and facilitating a low-carbon transition. However, onshore and offshore wind turbines in cold regions are prone to blade icing, which not only results in a decrease in power generation efficiency and an increase in blade load but also poses the risk of equipment damage. This study employed icing wind tunnel tests and numerical simulation methods to investigate the icing patterns and variations in aerodynamic performance under different blade materials, blade airfoils, and blade angles of attack. The results indicate that with the decrease in ambient temperature, the icing amount on aluminum alloy blades is significantly higher than that on glass fiber reinforced plastic (GFRP) blades; furthermore, the lower the ambient temperature, the smaller the difference in icing distribution characteristics between the two types of blades. When the blade angle of attack changes, the icing distribution characteristics on the blade surface exhibit significant variations. Under the condition of large angles of attack, the icing amount on the lower airfoil surface of the blade increases, while that on the upper airfoil surface decreases. Icing leads to a reduction in the airfoil lift coefficient and an increase in the drag coefficient, thereby causing a decline in the lift-to-drag ratio. With the extension of icing time, the aerodynamic performance of the blade continues to deteriorate. When the icing time reaches 5 min, the maximum reduction in the airfoil lift coefficient is 60.1%, the maximum increase in the drag coefficient is 40.9%, and the maximum reduction in the lift-to-drag ratio is 67.7%. In addition, the blade lift and drag coefficients undergo significant changes with the increase in the angle of attack. For airfoils with large angles of attack, a distinct phenomenon of advanced flow separation is observed after icing. This study can provide a data foundation for research on icing characteristics of wind turbine blades in cold regions and the subsequent development of anti-icing and de-icing methods. Full article

Icing phenomena occur on aircraft and unmanned aerial vehicles (UAVs) under extreme weather conditions. Ultrasonic detection technology is an effective method for measuring ice formation while maintaining the shape of the structure. However, current ultrasonic sensors, which are large and inflexible, are unsuitable for irregular UAV bodies, limiting their applications in real scenarios. For the detection of icing on curved structure, this study proposes a novel flexible ultra-thin ultrasonic transducer (FUTUT). The transducer exhibits excellent flexibility, making it suitable for use on high-curvature wings. Firstly, the FUTUT was designed based on the material properties of the airframe and the sensitivity requirements for ice detection, following the design guidelines for 1-3 type piezocomposites. The fabrication process for the FUTUT was then investigated, and its flexibility and low-temperature resistance were tested. Finally, icing detection experiments were conducted in an icing wind tunnel (IWT), where the FUTUT of 9.82 MHz demonstrated an ice-thickness-detection sensitivity of 0.29 mm. Experimental results indicate that the FUTUT possesses superior flexibility and exhibits excellent stability in low-temperature environments. These results underscore the FUTUT’s promise for applications in ice detection on curved structures. Full article

The increasing prominence of blade icing in wind power generation within cold regions has positioned anti-icing coating technology as a key research focus. This study synthesised phase-change microcapsules using bio-wax as the core material and isophorone diisocyanate as the shell material via interfacial polymerisation. These microcapsules were then compounded with polyurethane to form an anti-icing coating, whose properties and anti-icing performance were systematically investigated. Key findings indicate that a 1% emulsifier concentration yielded microcapsules with a concentrated particle size distribution (≈20 μm). Microcapsules with a core-to-shell ratio of 7:3 exhibited optimal thermal storage performance, characterised by a melting enthalpy of 49.73 J/g and an encapsulation efficiency of 78%, establishing this as the optimal formulation. Icing wind tunnel tests demonstrated enhanced anti-icing efficacy with increasing microcapsule concentration. At 36% concentration, the coating achieved an anti-icing efficiency of 65.80% under conditions of −15 °C and 3 m/s wind speed, and 64.05% at −10 °C and 6 m/s. The coating maintained its effectiveness under high wind speeds, though its performance diminished with increased water spray flux. The coating functioned by delaying ice formation through phase-change heat release. It consistently demonstrated an anti-icing efficiency exceeding 60% across operational conditions −15 °C to −5 °C and wind speeds of 3–9 m/s. This work provides an efficient and environmentally friendly anti-icing solution for wind turbine blades in cold regions. Full article

In cold and highly humid regions, wind turbine blades (WTB) are susceptible to icing, which can have a significant impact on the security and economic operation of turbines. Therefore, precise and prompt icing status detection is pivotal for maintaining wind turbine operational normalcy. In this research, an improved PP-YOLOE network is developed for classifying and detecting the icing state of WTB. First, a dataset of WTB icing is constructed based on a wind tunnel laboratory and expanded to improve the generalization of the model. To enhance feature representation, the network architecture was improved by embedding a coordinate attention (CA) mechanism and integrating atrous spatial pyramid pooling (ASPP) to better capture multi-scale contextual information. Moreover, a key innovation of this work is the novel application of a particle swarm optimization (PSO) algorithm to systematically automate hyperparameter tuning. Through ablation experiments and comparative tests, the improved PP-YOLOE network demonstrates superior overall performance on this dataset, achieving a multiple average precision of 0.94. It surpasses the original model across multiple evaluation metrics, indicating a robust and meaningful enhancement. The improved PP-YOLOE network proposed in this study provides a promising and effective method for WTB icing detection. This work provides a paradigm for applying advanced deep learning techniques to enhance intelligent industrial inspection tasks. Full article

Ultra-high-voltage (UHV) transmission lines are prone to galloping and oscillations under ice and wind loads, posing risks to system reliability and safety. Accurate aerodynamic coefficients are essential for evaluating these effects, but conventional wind tunnel and CFD methods are costly and inefficient for practical applications. To address these challenges, this study develops a surrogate model for rapid and accurate prediction of aerodynamic coefficients for six-bundle conductors. Initially, a CFD model to calculate the aerodynamic coefficients of six-bundle conductors was proposed and validated against wind tunnel experimental results. Subsequently, Latin hypercube sampling (LHS) was employed to generate datasets covering wind speed, icing shape, icing thickness, and wind attack angle. High-throughput numerical simulations established a comprehensive aerodynamic database used to train and validate multiple tree-based surrogate models, including decision tree (DT), random forest (RF), extremely randomized trees (ERTs), gradient boosted decision tree (GBDT), and extreme gradient boosting (XGBoost). Comparative analysis revealed that the XGBoost-based model achieved the highest prediction accuracy, with an R² of 0.855 and superior generalization performance. Feature importance analysis further highlighted wind speed and icing shape as the dominant influencing factors. The results confirmed the XGBoost surrogate as the most effective among the tested models, providing a fast and reliable tool for aerodynamic prediction, vibration risk assessment, and structural optimization in UHV transmission systems. Full article

This paper proposes a rotating test method to address the limitations of high costs and the inability to replicate high-speed multiphase environments in icing wind tunnels and artificial climate chambers. The method simulates high-speed multiphase in an enclosed space using relative motion and duct regulation at a lower cost. Using the FQJG2-30/16-400 type roof insulator, the Eulerian–Eulerian and CFD (computational fluid dynamics) method was employed to compare the proposed rotating method with traditional linear airflow tests in wind–sand erosion and high-speed icing experiments. Results show maximum differences of 3.23% in the collision rate and 4.34% in the icing mass, indicating good consistency. Validation experiments in an artificial climate chamber further confirmed the feasibility of the rotating test method, with icing mass differences within 5–8%. This study provides a cost-effective approach for high-speed testing in multiphase environments. Full article

Icing on eight-bundled conductors can significantly alter their aerodynamic behavior, potentially leading to structural instabilities such as galloping. This study employed wind tunnel experiments and numerical simulations to analyze the aerodynamic parameters of each iced conductor across various angles of attack. The simulations incorporated detailed stranded conductor geometries to assess their influence on aerodynamic accuracy. Incorporating stranded geometry in simulations reduced average errors in lift and drag coefficients by 45–50% compared to smooth models. The Den Hartog coefficient prediction error decreased from 15.6% to 3.9%, indicating improved reliability in oscillation predictions. Additionally, conductors with larger windward areas exhibited more pronounced wake effects, with lower sub-conductors experiencing greater wake interference than upper ones. The above results illustrate that explicit modeling of stranded conductor surfaces enhances the precision of aerodynamic simulations, providing a more accurate framework for predicting icing-induced galloping in multi-bundled conductors. Full article

This paper presents a preliminary investigation into the aeroelastic behavior of a tailless flying wing equipped with a rotating wingtip. Based on the configuration of Innovative Control Effectors (ICE) aircraft, an aeroelastic model of the tailless flying wing with a rotating wingtip has been developed. Both numerical simulation and wind tunnel tests (WTTs) are employed to study the aeroelastic characteristics of this unique design. The numerical simulation involves the coupling of computational fluid dynamics (CFD) and implicit dynamic approaches (IDAs). Using the CFD/IDA coupling method, aeroelastic response results are obtained under different flow dynamic pressures. The critical flutter dynamic pressure is identified by analyzing the trend of the damping coefficient, with a focus on its transition from negative to positive values. Additionally, the critical flutter velocity and flutter frequency are obtained from the WTT results. The critical flutter parameters, including dynamic pressure, velocity, and flutter frequency, are examined under different wingtip rotation frequencies and angles. These parameters are derived using both the CFD/IDA coupling method and WTT. The results indicate that the rotating wingtip plays a significant role in influencing the flutter behavior of aircraft with such a configuration. Research has shown that the rotation characteristics of the rotating wingtip are the primary factor affecting its aeroelastic behavior, and increasing both the rotation frequency and rotation angle can raise the flutter boundary and effectively suppress flutter onset. Full article