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Wind energy is essential for sustainable energy development, providing a clean and reliable energy source through the wind turbine. However, the vortices and turbulence generated as wind passes through turbines reduce wind speed and increase turbulence, leading to significant power losses for downstream turbines in wind farms. This study investigates wake characteristics in wind turbines by examining the effects of different scale ratios on wake dynamics, using both experimental and numerical approaches, utilizing scaled-down models of the Aeolos H-20 kW turbine at scales of 1:33, 1:50, and 1:67. The experimental component involved wind tunnel tests in an open-circuit tunnel with adjustable wind speeds and controlled turbulence intensity. Additionally, Computational Fluid Dynamics (CFD) simulations were conducted using STAR-CCM+ (Version 15.06.02) to numerically analyze the wake characteristics. Prior to the simulation, a convergence test was performed by varying grid density and y+ values to establish optimized simulation settings essential for accurately capturing wake dynamics. The results were validated against experimental data, reinforcing the reliability of the simulations. Despite minor inconsistencies in areas affected by tower and nacelle interference, the overall results strongly support the methodology's effectiveness. The discrepancies between the experimental results and CFD simulations underscore the limitations of the rigid body assumption, which does not fully account for the deformation observed in the experiment. [ABSTRACT FROM AUTHOR]

With global urbanization accelerating, high-rise buildings have become a common feature in the urban landscape, especially in coastal cities, where they encounter unique wind-load challenges. This study aims to quantify the structural response and occupant comfort of a high-rise residential building under wind-induced accelerations by integrating wind tunnel testing with finite element analysis (FEA). The research focuses on critical response parameters, including displacement, acceleration, and stress, to evaluate the building's performance. Wind tunnel tests provided detailed wind pressure distribution data across the building's surface, while multi-degree-of-freedom and finite element models facilitated precise numerical simulations. The findings highlight a significant directional and temporal variability in wind-load responses, with the most pronounced effects observed at a wind-direction angle of 105° relative to the building's front-facing axis (0°). The study confirms that the combined application of wind tunnel tests and FEA offers a comprehensive approach to understanding wind-induced responses, essential for the scientifically accurate and effective design of high-rise structures. [ABSTRACT FROM AUTHOR]

A small-scale supersonic flight experiment vehicle named OWASHI is being developed at Muroran Institute of Technology as a flying testbed for verification of innovative technologies for high-speed atmospheric flights. Drag reduction in the transonic and supersonic regimes is quite crucial for attainability of its supersonic flights. This study aims to obtain configuration modification for transonic drag reduction on the basis of the so-called area rule. In order to prevent accumulation of compression waves, various profiles of the bottleneck and the bulge are designed by using arcs with constant and large radii and spline curves approximating them. Their effects are assessed through CFD analysis, wind tunnel tests, and wave drag analysis. As a result, an area-rule-based configuration with a sharpened conical nose and a large-radius bottleneck achieves significant drag reduction in a transonic Mach range, as well as 57-count (57 × 10−4) reduction at the design Mach number of 1.1. However, the drag reduction effects of bulges are small and apparent only in a narrow Mach range. On the other hand, in the practical vehicle configuration, rearward fuselage extension shows a large amount of drag reduction, whereas the addition of an intake cancels the drag reduction effects of area-rule-based configurations. [ABSTRACT FROM AUTHOR]

This study aims to comprehensively investigate the dynamic characteristics of the tower of a scaled wind turbine model through wind tunnel tests. A model was scaled from the NREL 5 MW prototype wind turbine with a geometric scale ratio of 1/75, based on the similarity rules in thrust coefficient and dynamic characteristics. A series of wind tunnel tests were carried out on the scaled wind turbine model under different operating conditions and parked conditions with different yaw angles, and the modal parameters of the scaled model were identified by the stochastic subspace identification method and rotor stop tests. It was found that the vibration response of the tower in the fore–aft direction achieved its maximum value when the yaw angle was 90° with feathered blades, while the tower vibration response in the side–side direction was relatively severe with the yaw angle ranging from 10° to 50°. These observations are found to be well aligned with the aerodynamic characteristics of the airfoil. Moreover, the experimental results indicate that the scaled wind turbine model can reflect the vibration responses of its full-scale counterpart in the fore–aft direction. The natural frequencies and mode shapes of the scaled model can be accurately identified by different methods, but the identified damping ratios are relatively scattered. [ABSTRACT FROM AUTHOR]

The development of rail transport necessitates expanding environmentally friendly infrastructure. However, specific challenges arise in desert and sandy regions. One innovative solution to manage the effects of windblown sand on desert railways is the use of hump slab track superstructure. This paper develops a solid–fluid aerodynamic model based on ANSYS Fluent 2021 R2 software to simulate the hump slab track during a sandstorm. The model is validated through wind tunnel testing. A case study of a railway sandstorm in the Shuregaz region of Iran is presented, evaluating various sandstorm parameters and hump heights to determine their impact on sand concentration and particle velocity within the sand transit channels. The results indicate that increasing the sand particle diameter (from 150 to 250 µm) leads to higher sand concentration (up to 40%) and lower sand movement velocity (up to 28%). These results have been observed with a higher incremental approach concerning the sand flow rate. Conversely, increasing sandstorm velocity (from 10 to 30 m/s) decreases sand concentration and increases sand movement velocity up to 80% and 150%, respectively. Additionally, a 25 cm hump height significantly enhances sand passage by creating larger channels. [ABSTRACT FROM AUTHOR]

In this study, we developed a wind load calculation program (WCP) capable of predicting wind loads with relative precision during the preliminary design phase. First, wind tunnel tests were conducted to identify the essential factors necessary for calculating wind loads and the variables influencing these factors. Square building shapes were considered, and the wind force coefficients and power spectral density were measured by combining four ground roughness values, eleven side ratios ( D / B ), four aspect ratios ( H / B D ), and wind directions ranging from 0° to 90°. The wind power coefficient and the spectral coefficient were formulated so that the wind load could be calculated according to various conditions. The WCP computations were based on the calculation of the load combination coefficient using the resonant wind load. Finally, the wind loads obtained from the wind tunnel tests were compared with those predicted by the WCP using an actual project model (inner-core (A) and outer-core (B) types). Building A yielded similar WCP and wind tunnel experimental responses when subjected to wind and laminar wind loads. Additionally, Building B yielded a larger error than that of Building A, but similar results were obtained when buildings were subjected to combination and laminar wind loads. [ABSTRACT FROM AUTHOR]

Aircraft secondary flow systems are small-flow circulation devices that are used for thermal and cold management, flow control, and energy generation on aircraft. The aerodynamic characteristics of main-flow-based inlets have been widely studied, but the secondary-flow-based small inlets, jets, and blowing and suction devices have seldom been studied. Two types of secondary flow systems embedded in a supersonic aircraft wing, a ram-air intake and a submerged intake, are researched here. Firstly, wind tunnel tests under subsonic, transonic, and supersonic conditions are carried out to test the total pressure recovery and total pressure distortion. Secondly, numerical simulations are used to analyze the flow characteristics in the secondary flow systems. The numerical results are validated with experimental data. The calculating errors of the total pressure recovery on the ram-air and submerged secondary flow systems are 8% and 10%, respectively. The simulation results demonstrate that the total pressure distortion tends to grow while the total pressure recovery drops with the increasing Mach number. As the Mach number increases from 0.4 to 2, the total pressure recovery of the ram-air secondary flow system decreases by 68% and 71% for the submerged system. Moreover, the total pressure distortion of the ram-air and submerged secondary flow systems is increased by 19.7 times and 8.3 times, respectively. Thirdly, a detailed flow mechanism is studied based on the simulation method. It is found that the flow separation at the front part of the tube is induced by adverse pressure gradients, which primarily determine the total pressure recovery at the outlet. The three-dimensional vortex in the tube is mainly caused by the change in cross-sectional shape, which influences the total pressure distortion. [ABSTRACT FROM AUTHOR]

A long-span double-deck steel truss suspension bridge is easy to produce vortex-induced vibration (VIV) at low air velocity, which affects bridge service life. Additional aerodynamic measures play a role in suppressing VIV by changing the aerodynamic shape, which is a common control method. As the main aerodynamic measure to suppress the VIV response, wind fairing is widely used in engineering practice. In order to obtain the optimal additional position and shape parameters of the fairing, Huangjuetuo Yangtze River Bridge is the research target. Through the combination of a wind tunnel test and numerical simulation, the VIV response of the original and fairing section is studied. Based on data analysis, it is revealed that these additional fairings to the upper chord can significantly reduce the VIV response. When the shape parameters of the fairing are h/D = 1/4 and l/D = 1, the VIV inhibition efficiency is the highest, which can reach 65.51%. By analyzing the flow distribution, it can be seen that VIV is caused mainly by vortex separation in the upper bridge board area. Although this wind fairing does not change the original vortex shedding forms, it changes the first separation point and movement direction of the airflow, making the vortex scale generated by the airflow smaller and the vorticity lower, thus effectively suppressing VIV. [ABSTRACT FROM AUTHOR]

A multibladed drag-based Vertical Axis Wind Turbine (VAWT) was developed and its startup dynamics evaluated using wind tunnel tests. The experimental data obtained for the time-based angular position of the rotor shaft at Aberdeen's average wind speed of 6 m/s show an initial rapid acceleration of the VAWT due to the drag force being exerted on the rotor blades. This acceleration becomes more gradual until the VAWT reaches its peak rotational speed of 85 rpm in 30 s, which corresponds to an operating tip speed ratio (TSR) of 0.42. The operating TSR of the VAWT was found to be 27% higher than previously reported in numerical studies. [ABSTRACT FROM AUTHOR]

The vibrissae of harbor seals exhibit a distinct three-dimensional structure compared to circular cylinders, resulting in a wave-shaped configuration that effectively reduces drag and suppresses vortex shedding in the wake. However, this unique cylinder design has not yet been applied to wind power technologies. Therefore, this study applies this concept to the design of downwind wind turbines and employs wind tunnel testing to compare the wake flow characteristics of a single-cylinder model while also investigating the output power and wake performance of the model wind turbine. Herein, we demonstrate that in the single-cylinder test, the bionic case shows reduced turbulence intensity in its wake compared to that observed with the circular cylinder case. The difference in the energy distribution in the frequency domain behind the cylinder was mainly manifested in the near-wake region. Moreover, our findings indicate that differences in power coefficient are predominantly noticeable with high tip speed ratios. Furthermore, as output power increases, this bionic cylindrical structure induces greater velocity deficit and higher turbulence intensity behind the rotor. These results provide valuable insights for optimizing aerodynamic designs of wind turbines towards achieving enhanced efficiency for converting wind energy. [ABSTRACT FROM AUTHOR]

In aeolian sand movement, the vertical distribution of sand particle size is intricately linked to sand flux, wind–sand flow field and dune development. In the present study, the distribution characteristics of sand grains in four particle size ranges at nine heights were investigated through sand blowing tests at five different reference wind speeds. The correlation between sand particle size and wind speed indicates that when the particle size was ≥0.35 mm, there was a linear variation of mass percentage with wind speed. When the particle size was <0.35 mm, when Z ≤ 0.15 m, a linear variation of mass percentage with wind speed was found; when Z > 0.15 m, an exponential modification in mass percentage with wind velocity was observed for sand grains falling within this specific range of particle sizes. The correlation between sand particle size and height indicates that when the reference wind speed was ≥15 m/s, the mass percentage of sand particles varied linearly with height. When the reference wind speed was ≤13.5 m/s, the mass percentage of sand grains with particle size in the 0.25–0.35 mm range increases first and then decreases with increasing height. The present results can provide a reference for subsequent research on the aerodynamic characteristics of wind–sand flow fields and on the mechanism of dune formation. [ABSTRACT FROM AUTHOR]

Featured Application: The study can further guide the application of vortex isolation plates in wind-induced vibration of twin-box girders. Twin-box girders are a good option for long-span cable-bearing bridges due to their excellent stability. Nonetheless, the girder's slots may generate vortex-induced vibrations (VIVs). Fortunately, appropriate aerodynamic measures can effectively suppress the VIVs in twin-box girders while reducing costs. To examine the effects of vortex isolation plates with varying aperture diameters and opening ratios on the VIVs, a segment model wind tunnel test was conducted. The results demonstrated that a reduction in the opening ratio improved the performance under heaving VIVs, but there was no discernible trend under torsional vibrations. It was also discovered that the opening size significantly influences the length of the lock-in region of torsional vibrations. Furthermore, heaving VIVs have a substantial correlation with both of the girder's boxes, while torsional vibrations are mostly connected with the downstream section. [ABSTRACT FROM AUTHOR]

Wind tunnel tests and numerical simulations are the mainstream methods to study the wind-induced vibration of structures. However, few articles use statistical parameters to point out the differences and errors of these two research methods in exploring the wind-induced response of membrane structures. The displacement vibration of a saddle membrane structure under the action of wind load is studied by wind tunnel tests and numerical simulation, and statistical parameters (mean, range, skewness, and kurtosis) are introduced to analyze and compare the displacement data. The most unfavorable wind direction angle is 0° (arching direction). The error between experiment and simulation is less than 10%. The probability density curve has a good coincidence degree. Both the test and simulation show a certain skewed distribution, indicating that the wind-induced vibration of the membrane does not obey the Gaussian distribution. The displacement response obtained by the test has good stability, while the simulated displacement response has strong discreteness. The difference between the two research methods is quantitatively given by introducing statistical parameters, which is helpful to improve the shortcomings of wind tunnel tests and numerical simulations. [ABSTRACT FROM AUTHOR]

Icing is a common physical phenomenon, and the icing of wind turbine blades can significantly affect the performance of wind turbines. Therefore, researching methods to prevent icing is of great significance, and the coating method of anti-icing is an effective way to delay icing, with advantages such as low energy consumption and easy implementation. In this study, using the coating method as the background, tetradecane phase change microcapsules were prepared, with a melting enthalpy of 90.8 J/g and a crystallization enthalpy of 96.3 J/g, exhibiting good coverage and energy storage efficiency. After mixing tetradecane phase change microcapsules (PCMS) with polyurethane coating (PUR) and coating them on wind turbine blades, after a 5 min icing wind tunnel test, the coating could significantly delay the icing on the blade surface, with the highest anti-icing rate reaching 60.41%. This indicates that the coating has a good anti-icing effect and provides basic research data for exploring new anti-icing methods. [ABSTRACT FROM AUTHOR]

Offshore wind turbines operating in frigid and humid climates may encounter icing on the blade surface. This phenomenon adversely impacts the aerodynamic efficiency of the turbine, consequently diminishing power generation efficacy. Investigating the distribution characteristics of icing on the blade surface is imperative. Hence, this study undertook icing wind tunnel tests on segments of DU25 airfoil, a prevalent type for offshore wind turbines, to examine such characteristics as different chord lengths and angles of attack. The results show a simultaneous increase in the blade icing area and growth rate of the net icing area with augmenting the chord length and angles of attack. The total icing area rate decreases by a factor of two when the chord length is doubled. The relative positioning of icing and the average icing thickness remain consistent across the airfoil blades with varying chord lengths. Comparing the icing shapes on blades of varying scales shows a similarity ranging from 84.06% to 88.72%. The results of this study provide insight into the icing characteristics of offshore wind turbines. [ABSTRACT FROM AUTHOR]

In recent years, the outbreak of infectious diseases has highlighted the need for improved planning of hospital buildings. Traditional planning for infectious disease hospitals only considers the impact of wind and pollutant diffusion, without analysing pollutant diffusion under different thermal conditions. To reveal the distribution of pollutants in infectious disease hospitals under different thermal conditions, this study conducted wind tunnel tests and numerical analyses of pollutant diffusion in the environment surrounding an infectious disease hospital in Changsha, China. The results show that the pollutant concentration mainly depends on the local wind speed. In the range of Rb = −1.25 to 1.25, the concentration of pollutants was mainly affected by the disturbance of the flow field in areas with rough surfaces, where the effect of the thermal stability of the atmosphere on pollutant diffusion was relatively small. However, in relatively flat regions, the thermal stability of the atmosphere played a significant role in pollutant diffusion around the buildings. [ABSTRACT FROM AUTHOR]

In aerodynamics, characterizing the aerodynamic behavior of aircraft typically requires a large number of observation data points. Real experiments can generate thousands of data points with suitable accuracy, but they are time-consuming and resource-intensive. Consequently, conducting real experiments at new input configurations might be impractical. To address this challenge, data-driven surrogate models have emerged as a cost-effective and time-efficient alternative. They provide simplified mathematical representations that approximate the output of interest. Models based on Gaussian Processes (GPs) have gained popularity in aerodynamics due to their ability to provide accurate predictions and quantify uncertainty while maintaining tractable execution times. To handle large datasets, sparse approximations of GPs have been further investigated to reduce the computational complexity of exact inference. In this paper, we revisit and adapt two classic sparse methods for GPs to address the specific requirements frequently encountered in aerodynamic applications. We compare different strategies for choosing the inducing inputs, which significantly impact the complexity reduction. We formally integrate our implementations into the open-source Python toolbox SMT, enabling the use of sparse methods across the GP regression pipeline. We demonstrate the performance of our Sparse GP (SGP) developments in a comprehensive 1D analytic example as well as in a real wind tunnel application with thousands of training data points. [ABSTRACT FROM AUTHOR]

The transition characteristics of a modified RAE5243 airfoil were investigated using a wind tunnel test and numerical simulations. Transition detection is of great significance for the assessment of drag reduction. In wind tunnel tests, transition location can be detected by infrared thermography. However, in subsonic and transonic wind tunnel tests, the temperature difference between the laminar flow region and turbulent flow region is small. Moreover, the test models are usually made of metals, which make the transition location hard to identify. Combined with infrared thermography, a carbon nanotube heating coating powered by electricity was used to detect the transition location of a modified RAE5243 airfoil wing. The effects of heating power, angle of attack (AOA), and Mach number were studied. The results show that heating power has no impact on transition location. As the AOA increases, the transition location moves forward. With an increase in Mach number, the transition location moves forward first and then backward, and it reaches its most forward point at Ma = 0.75. The results of our numerical simulations indicate that, at Ma ≥ 0.75, a shock wave appears on the wing, and the transition is closely related to the shock wave rather than the adverse pressure gradient. [ABSTRACT FROM AUTHOR]

Developing wind tunnel models is time consuming, labor intensive, and expensive. Rapid prototyping for wind tunnel tests is an effective, faster, and cheaper method to obtain aerodynamic performance results while considerably reducing acquisition time and cost for the models. Generally, the rapid prototyping models suffer from insufficient stiffness or strength to withstand the loads generated during a wind tunnel test. In the present study, a rapid prototype model reinforced with metallic inserts was produced to experimentally investigate the aerodynamic characteristics of an uncrewed aerial vehicle with various wingtip deflections. The fused deposition modeling process was used to make the outer mold, whereas the metallic parts were produced using laser cutting and the computer numerical control machining process. Then, the model was evaluated both experimentally and numerically. The test campaign presented in this work was conducted in the de Havilland low-speed wind tunnel facility at the University of Glasgow. For better characterization of flow patterns dominated by leading edge vortices, numerical simulations were run using OpenFOAM 8.0 and validated with experimental data. The experimental data obtained from the hybrid rapid-prototyped model agreed well with the numerical results. This demonstrates the efficacy of hybrid rapid-prototyped models in providing reliable results for initial baseline aerodynamic database development within a short period and at a reduced cost for wind tunnel tests. [ABSTRACT FROM AUTHOR]

A thousand-meter-high megatall building, which consists of three tear-drop-shaped towers arranged in an equilateral triangle and a central circular tower, has ten outdoor platforms along the height at an interval of 100 m to connect the four towers. As the pedestrian-level wind environment around the outdoor platforms of high-rise buildings has been less studied for higher incoming wind speeds than those of the ground wind, it is necessary to conduct the related research and evaluations of the pedestrian-level wind environment around outdoor platforms to ensure pedestrian comfort and safety. First, based on the flow field analysis of the megatall building model, potential aerodynamic measures are proposed to improve the pedestrian-level wind environment of outdoor platforms. Then, the wind tunnel test and CFD simulation of outdoor platforms are conducted with five aerodynamic measures, and an averaged adjustment coefficient is put forward to establish the link between the full model and the sub-configuration model for the wind speed amplification factor, Ri, greater than 1.0, so the data obtained from the wind tunnel test can be transformed for further assessment of the pedestrian-level wind environment. Finally, the Lawson criterion was used to quantitatively analyze and compare the effects of five aerodynamic measures to improve the wind environment, thus providing a design that satisfies the requirements of "wind comfort" and "wind safety" for the thousand-meter-high megatall pedestrian platform. This study contributes to the further understanding of pedestrian-level wind environment characteristics of outdoor platforms and the potential aerodynamic measures to improve wind comfort and wind danger. [ABSTRACT FROM AUTHOR]

Ice accumulation significantly impacts the mechanical properties of wind turbine blades, affecting power output and reducing unit lifespan. This study explores the icing characteristics and their effects on a 1.5 megawatt (MW) wind turbine blade's mechanical properties under various conditions, including wind speeds of 5 m per second (m/s) and 10 m per second, temperatures of −5 degrees centigrade (°C) and −10 degrees centigrade, and different liquid water contents, by using icing wind tunnel tests and structural statics analysis. The research reveals that ice predominantly forms in an irregular pattern on the leading edge of the blade. It is easy to produce corner ice and ice skating when the icing temperature and wind speed are higher, and the icing surface is rougher. When the other conditions remain unchanged, the decrease in temperature, an increase in wind speed, or a rise in liquid water content all lead to an increase in the average thickness of icing and the volume of icing at the leading edge, with the effect of the wind speed on the two being 147.8% and 147.9%, the effect of the liquid water content on the two being 39.9% and 53.5%, and the effect of the temperature on the two being 24.6% and 13.2%. The study finds that the blade tip experiences the maximum displacement in both iced and non-iced states, although the positions of peak equivalent stress and strain vary. The above study will also provide references for the design of new wind turbine blades and the anti-icing maintenance of wind turbine generator sets. [ABSTRACT FROM AUTHOR]

For this paper, full-scale/model test comparisons to validate the traditional atmospheric boundary layer (ABL) wind-tunnel simulation technique performed until now by the wind engineering community are systematically reviewed. The engineering background includes some benchmark low-rise buildings specifically established for use in wind engineering research (the Aylesbury experimental buildings, the Texas Tech University experimental building, the Silsoe buildings, etc.), several high-rise buildings in North America and East Asia, long-span bridges, large-span structures, and cooling towers. These structures are of different geometries, are located in different wind environments, and are equipped with various transducers and anemometers. By summarizing the different articles in the literature, it is evident that notable discrepancies between the full-scale measurement and the model test results were observed in most full-scale/model test comparisons, which usually took certain forms: the mean and/or the peak negative pressures at the flow separation regions on buildings were underestimated in the wind tunnel; differences in the root-mean-square (rms) values of the acceleration samples between the full-scale measurements and the force balance model tests were non-negligible; the vertical vortex-induced vibration amplitudes of bridges measured using section models and aero-elastic models were much lower than those observed on the prototypes, etc. Most scholars subjectively inferred that inherent technical issues with the ABL wind tunnel simulation technique could be responsible for the observed full-scale/model test discrepancies, including the Reynolds number effects, the turbulent flow characteristics effects, and the non-stationarity effects. However, based on the authors' years of experience and after discussion with experienced researchers, it was found that some of the full-scale measurements performed in earlier research were inherently less accurate and deterministic than the wind tunnel experiments they were supposed to validate, which could also be a significant cause of the full-scale/model test discrepancies observed. It is suggested herein that future studies in this field should regard full-scale measurements only as benchmarks, and that future works should focus on synthesizing the results from different schools of physical experiments and formulating universal empirical models of high theoretical significance to properly validate future wind tunnel tests. [ABSTRACT FROM AUTHOR]

A monopile is the most popular foundation type for wind turbines. However, the dynamic performance of monopile-supported wind turbines under different operating and ground conditions is not fully understood. In this study, an integrated monopile-supported wind turbine model in a wind tunnel was employed to jointly simulate the operating and ground conditions. A series of wind tunnel tests were designed and performed to investigate the dynamic performance of monopile-supported wind turbines. These tests included seven operating conditions (seven wind speeds and corresponding rotor speeds) and four ground conditions (one fixed ground condition and three deformable ground conditions with different soil relative densities). According to the test results, the structural responses and dynamic characteristics were analyzed and discussed. This shows that the assumption of fixed-base support significantly overestimates the natural frequency but underestimates the global damping ratio. With the increase in soil relative density, the natural frequency slightly increases, while the damping ratio decreases more significantly. With the increase in the wind speed and rotor speed, the increase in global damping is larger on softer ground. A regression analysis was performed to estimate the global damping ratio under different operating and ground conditions. [ABSTRACT FROM AUTHOR]

The concept of the Fan Wing, a novel aircraft vector-force-integrated device that combines a power unit with a fixed wing to generate distributed lift and thrust by creating a low-pressure vortex on the wing's surface, was studied. To investigate the unique propulsion mechanism of the Fan Wing, a Fan Wing test platform was developed, and experiments were conducted in a wind tunnel. At the same time, numerical simulations were established. In order to further improve the aerodynamic efficiency of the Fan Wing and decouple the control of lift and thrust, an improved scheme for the leading-edge structure of the Fan Wing was proposed, and a numerical analysis was conducted. A Fan Wing unmanned aerial vehicle (UAV) was designed and manufactured using the Fan Wing as the source of lift and thrust for the aircraft, and flight verification was conducted. The wind tunnel tests have proven that the main factors influencing the lift and thrust of the Fan Wing are rotation speed of cross flow fan, angle of attack, and incoming flow. The numerical analysis results of slotting on the leading edge show that the lift and thrust of the Fan Wing can be improved, but also the strength and position of the low-pressure vortices can be controlled. The results of flight tests show that the distributed lift and thrust of the Fan Wing can be directly applied to aircraft without the need for additional propulsion devices. In summary, the aerodynamic characteristics of the Fan Wing can be applied to electric short takeoff and landing (E-STOL) scenarios in urban air traffic. [ABSTRACT FROM AUTHOR]

Due to the tall and large superstructures of cruise ships, the wind-induced vibration of frame structure on open decks cannot be neglected. This study investigated the wind-induced vibration of a typical frame structure on a cruise ship by using wind tunnel tests and numerical simulations. Wind tunnel tests were conducted to explore the simulation methods of the fluid–structure interaction (FSI). CFD simulations were performed to obtain the wind field data of the entire ship, which was utilized as an input for the open deck through the subdomain method. Subsequently, wind-induced vibration simulations of the guide rail frame structure on the open deck was carried out under various wind conditions. The results revealed that employing the turbulence model SST k-ω had a good agreement with the experimental data. The entire ship's CFD results have a significant impact on the subdomain's wind-induced vibration results. The vibration frequency of the guide rail frame structure was mainly concentrated between 0.8–10.1 Hz. The most unfavorable conditions appear at the wind attack angles of 0° and 120°. This study can provide some instructive insights for the prediction of wind-induced vibration and control of typical structures on the open decks of large cruise ships. [ABSTRACT FROM AUTHOR]

To investigate the flow control characteristics of antiphase pulsed jet technology and explore a more efficient method to control unsteady flow with minimal impact on flow turbulence, wind tunnel experiments were conducted. The aim was to address the issue of flow separation control on the surface of a cylindrical model. The model had a diameter of 100 mm, and an experimental setup utilizing an antiphase pulsed jet excitation was developed. The optimisation of unsteady jet control involved adjusting parameters such as jet momentum coefficient, slot position, and excitation frequency. The flow separation control effect on the cylinder surface was compared between in-phase and antiphase pulsed jet using a particle image velocimetry (PIV) technique. The mechanisms of flow control for these two methods were analysed. The results showed that in still air, increasing the jet momentum led to a gradual decrease in the high-velocity region, which also moved away from the wall. Under incoming flow conditions, positioning the slot closer to the separation point resulted in better flow separation control, particularly when the excitation frequency matched the main flow frequency. Both in-phase and antiphase pulsed jet excitations effectively suppressed flow separation. In the near-wall region within the symmetric plane between the two slots, the antiphase excitation reduced the root mean square of velocity fluctuations by approximately 1.9% and increased the average velocity by approximately 15.5% compared to in-phase pulsed jet excitation. In-phase pulsed jets exhibited low-frequency, high-velocity characteristics near the separation point, while antiphase pulsed jets, due to the alternating discharge of the two jets, had a lesser impact on the flow field turbulence. [ABSTRACT FROM AUTHOR]

Featured Application: A normalized across-wind fluctuating wind load spectrum model is proposed, taking into account the effects of incoming turbulence, the side ratio, vortex shedding, and separation reattachment flow-induced spectral bandwidth changes and high-frequency fluctuations. The present work is devoted to the role of boundary layer turbulence on the spectral characteristics of fluctuating wind loads on large aspect-ratio rectangular prisms. Seven rectangular rigid models with different side ratios (1/4~4) were created, and simultaneous pressure experiments were conducted under the boundary layer turbulence flows. Using the measured data, the power spectrums of the fluctuating aerodynamic forces were calculated, and then, the spectral characteristics under different turbulent boundary layer flows were analyzed. In contrast to the typical power spectrum model, the main factors affecting the spectral characteristics of the fluctuating aerodynamic loads are presented and discussed in this study. The power spectrum of the rectangular prism was significantly impacted by the turbulent wind field, primarily because higher turbulence intensity levels result in a lower spectral peak and a wider spectral bandwidth, which also redistributes spectral energy. In particular, the effect on the spectral properties of across-wind fluctuating loads was stronger, and the turbulent disturbance modified the lateral separation flow structure, causing the reattachment phenomenon to occur earlier on rectangular prisms with small side ratios, which effectively altered the spectral properties. Thus, a normalized across-wind fluctuating wind load spectrum model is proposed, taking into account the effects of incoming turbulence, the side ratio, vortex shedding, separation reattachment flow-induced spectral bandwidth changes, and high-frequency fluctuations. [ABSTRACT FROM AUTHOR]

When examining the history of wind engineering, it is evident that many full-scale/model test comparisons have found noticeable differences between the results. Although understanding the causes of these differences is important for practical purposes, limited numerical and experimental conditions have often resulted in subjective explanations for full-scale/model test comparisons without scientific validation. To address this issue, this article suggests the use of the computational fluid dynamics technique or the multiple-fan actively controlled wind tunnel technique to quantitatively reveal the adverse effects that impact the reliability of the traditional atmospheric boundary layer wind tunnel tests for a large cooling tower, including not only the widely acknowledged influences (Reynolds number effects and turbulent flow characteristics effects) but also the non-stationarity effects that have potential influences. Established on the novel proposition, a new research scheme for future full-scale/model test wind effects comparisons for large cooling towers has been formulated based on the numerical or physical simulations of the sinusoidal flow fields. Using the Pengcheng cooling tower as a case study, the research recognized the very significant impact of Reynolds number effects, the non-stationarity effects that cannot be ignored, and the negligible effects of turbulent flow characteristics. [ABSTRACT FROM AUTHOR]

This paper carried out wind tunnel tests and numerical analysis to study the effect of the spatial position of deflector plates on the vortex-induced vibration (VIV) of a double-deck truss girder. The wind tunnel tests found that setting the web deflector plate and the lower chord deflector plate significantly suppressed the VIV. In order to study the suppression mechanism of the deflector plate on VIV, numerical simulations were conducted using the computational fluid dynamics (CFD) method. We analyzed the suppression mechanism of the deflector plate on VIV by combining the vertical amplitude obtained by numerical simulation with the change in the vorticity magnitude and direction. The results showed that the flow velocity around the lower surface of the airflow was reduced, resulting in significantly lower vorticity at the exact position of the lower chord deflector plate and web deflector plate section compared to the original section. The web deflector plate and the lower chord deflector plate broke the vortex shedding mode in the wake flow region, and the vortex shedding frequency was far away from the self-oscillation frequency of the double-deck truss girder, thus suppressing the VIV. [ABSTRACT FROM AUTHOR]

High-rise residential buildings often adopt rectangular cross-sections with large depth-to-width ratios. Moreover, the cross-sections have many grooves and chamfers for better ventilation and lighting. However, related research is lacking. This study performed wind tunnel tests and large eddy simulations (LES) on two typical buildings to analyze the surface wind pressures and flow fields around the buildings. The base moment spectra, along with the wind pressure coefficients, demonstrate that numerical simulation is capable of accurately representing the magnitudes and variations in wind loads along the height of the building. Furthermore, numerical simulation effectively captures the dominant energy distribution characteristics of fluctuating wind loads in the frequency domain. The shear layer separations, vortex shedding and reattachment phenomenon were observed. It was found that in the middle and lower parts of the buildings, the shear layer separation changed dramatically. Buildings with depth-to-width ratios close to 2 are minimally affected by changes in wind direction. However, for buildings with larger depth-to-width ratios, especially when the short side faces the wind, the reattachment of the shear layer and the shedding of wake vortices become crucial factors in generating fluctuating cross-wind loads. This emphasizes the significant impact of wind direction and plan dimensions on flow characteristics and aerodynamic behavior. When the building contained corners and grooves, the low-wind-speed area induced by the shear layer separation shrank and the reattachment point shifted closer to the windward facade. [ABSTRACT FROM AUTHOR]

Large-span suspension bridges are susceptible to wind loads. Therefore, a more precise analysis of their wind-induced vibration response is necessary to ensure the structure's absolute safety. This investigation conducted wind tunnel tests for the construction and completion stages to reveal the vortex-induced vibration (VIV) phenomenon of a double-deck suspension bridge. The results showed that no VIV occurred during the construction stage. However, the inclusion of railings significantly deteriorated the aerodynamic performance of the suspension bridge, leading to significant VIV at +3° and +5° wind angles of attack. Additionally, reducing the railing ventilation rate can significantly suppress the VIV amplitude. A new analysis method based on computational fluid dynamics (CFD) simulation is proposed to investigate the VIV mechanism of the double-deck truss girder. Twenty-nine measurement points were used to explore the vortex that causes VIV. The numerical simulations found that the area above and aft of the upper deck dominated the vertical VIV, while the aft of the lower deck dominated the torsional VIV. Furthermore, the intensity of the vortex in these areas was significantly lower during the construction stage. Moreover, reducing the railing ventilation rate significantly suppresses the torsional VIV by reducing the intensity of the vortex in the region behind the lower deck. [ABSTRACT FROM AUTHOR]

This article presents the results of experimental and numerical studies on a single coherent rotor blade. The blade was designed for a vertical-axis wind turbine rotor with a self-adjusting system and planetary blade rotation. The experimental tests of the full-scale blade model were conducted in a wind tunnel. A computational fluid dynamics (CFD) analysis of the blade's cross section was then carried out, including the boundary conditions corresponding to those adopted in the wind tunnel. The main objective of the study was to determine the aerodynamic forces and aerodynamic moment for the proposed single coherent cross-section of the blade for the carousel wind rotor. Based on the obtained results and under some additional assumptions, the driving torque of the wind rotor was determined. The obtained results indicated the possibility of using the proposed blade cross-section in the construction of a carousel wind rotor. [ABSTRACT FROM AUTHOR]

To investigate the wind-induced response and equivalent wind load of a super-tall building, an aeroelastic model of the building was designed to measure aerodynamic interference in wind tunnel tests. Experiments on pressure and vibration measurements were conducted in both uniform and turbulent wind fields, and the displacement response and surface wind pressure at different locations of the model were recorded. The displacement time-history response spectrum and aerodynamic spectrum in both fields were compared and analyzed. The research showed that the mean displacement responses of the model in the across-wind and along-wind directions gradually increased with velocity under different wind attack angles. The mean displacement response of torsion moment in a uniform wind field changed very little, and the mean and fluctuating wind pressures in each layer were significantly stratified, making it is easy to generate a coupled vortex-induced resonance. On the other hand, the mean displacement response of torsion moment in a turbulent field increased with wind velocity. Strong turbulence made the fluctuating wind pressure at the top and bottom of the model slightly more significant than in a uniform field. The resistance of super-tall buildings came from turbulence excitation in the along-wind direction and the self-excited resistance generated by the across-wind direction. The test methods and main research conclusions may provide a reference for glass curtain walls and the structural wind-resistant design of super-tall buildings. [ABSTRACT FROM AUTHOR]

In this study, the flow patterns and fluctuating wind pressure characteristics around the roof of a spherical dome with a low rise–span ratio (f/D) were analyzed in detail. Significant differences were observed when compared to the results of previous studies on spherical dome roofs with relatively high f/D. The flow-pattern-based zone divisions and zone-specific pressure spectra models proposed in previous studies have limitations when applied to a spherical dome with an f/D ratio of 0.1, which is the subject of this study. Therefore, this study modified and proposed zone division and pressure spectra modeling methods based on the zone division and pressure spectra models of previous studies, and applied them to spherical dome roofs with a low rise–span ratio. Based on spectral statistics, the average error between the measured and simulated spectra was less than 4%, demonstrating high accuracy. [ABSTRACT FROM AUTHOR]

This research investigates the cross-wind aeroelastic effects of tall buildings with hexagonal cross-sections by using aeroelastic models with multiple-degree-of-freedom (MDOF). Cross-wind displacement and acceleration responses at the top of each model are measured using the wind tunnel test. The aerodynamic damping ratios for the two representative wind directions are identified by analyzing the measured responses using the random decrement technique. Results show that large-amplitude vortex-induced vibrations occur for one of the representative wind directions where the vertex of the hexagonal model is against the approaching wind, while there is no significant VIV observed for the other representative wind direction where the face of the hexagonal model is perpendicular to the approaching wind. The most dangerous wind direction is then identified based on the discussion. Two expressions for the cross-wind aerodynamic damping ratio are established for the two wind representative wind directions. The two equations can be used in engineering practice to estimate the cross-wind aerodynamic damping ratio of hexagonal tall buildings. [ABSTRACT FROM AUTHOR]

A new idea of nosebleed air jets with strong coupled internal and external flow is put forward using the lateral jet control principle to improve the maneuverability and fast reaction capabilities of hypersonic vehicles. The hypersonic vehicle's nose stagnant high-pressure and high-temperature gas is utilized as the drive source for long-term jet control. The significant coupled jet interaction of the internal and external flow changes the aerodynamic characteristics. As a result, the structure is basic and does not rely on any external source to achieve flight attitude control. The complicated flow characteristics of the nosebleed jet in supersonic crossflow surrounding the vehicle were numerically and experimentally investigated. The jet interaction characteristics and the aerodynamic characteristic changes generated by the nosebleed air jet are verified by comparing the flow field with and without the jet. Results indicate that the nosebleed air jet alters the center-of-pressure coefficient, which is subsequently coupled with the interference aerodynamic force. This results in a variation in pitch moment. The jet decreases the pitching moment coefficient when compared with the case without a jet. It is probable that combining nosebleed air jets with model centroid adjustment yields an optimal trim angle of attack. [ABSTRACT FROM AUTHOR]

In order to investigate the output power and wake velocity of small multi-rotor wind turbines compared to single-rotor wind turbines, which operate in the same swept area at various blade tip distances, this paper used the wind tunnel test method to examine single-rotor wind turbines with diameter D of 0.4 m and 0.34 m corresponding to the triple-rotor wind turbines and double-rotor wind turbines with a single rotor diameter D of 0.24 m, respectively. The experimental results indicated that, without rotation speed control, the triple-rotor wind turbine produced more power than the single-rotor wind turbine with an equivalent swept area and that the output power tended to rise initially and then fall as the distance between each rotor increased. Moreover, the power increase reached a maximum of 8.4% at the 0.4D blade tip distance. In terms of wake measurement, triple-rotor wind turbines had smaller wake losses and faster recovery rates than single-rotor wind turbines. The smaller the blade tip distance, the earlier the wake merged and fused and the faster the recovery rate. In designing small multi-rotor wind turbines, the above discussion can serve as a guide. [ABSTRACT FROM AUTHOR]

In view of the deficiency of the quasi-steady galloping critical wind speed calculation method based on the classical Den Hartog criterion, this paper proposes a quasi-steady galloping stability analysis method that considers the wind attack angle criterion (dCV/dα) through theoretical analysis. Firstly, the tri-component force coefficients of a square-section model were measured through wind tunnel tests, and the galloping force coefficients calculated with three different galloping criteria (the dCV/dα criterion, Den Hartog criterion, and Xie criterion) were compared and analyzed. Secondly, to further verify the reliability and applicability of the criteria proposed in this study, wind tunnel tests and numerical simulations were conducted on an H-shaped section. The verification results of the H-shaped section showed that under the action of the incoming flow at a large angle of attack of 70°, the maximum error of the classic Den Hartog criterion could reach about 44%. This study used the dCV/dα criterion while considering the large angle of attack of the incoming flow, and its calculation error could be controlled within 10%. At the same time, the numerical simulation showed that there was serious aerodynamic instability in this section under the critical wind speed. A pair of periodic vortex structures were formed in the wake region of the H-shaped section, resulting in constant generation and separation phenomena, which induced structural instability. [ABSTRACT FROM AUTHOR]

A variable geometry auxiliary inlet for a wide-body aircraft environmental control system with moveable deflectors operating in a large mass flow rate range is studied through numerical simulation and wind tunnel tests, which yields a design method for the variable geometry auxiliary inlet with high performance. The characteristics of the flow field are studied by numerical simulation. The results show that the favorable pressure gradient and the roll-up vortices are the major impetus that inhales the incoming flow into the inlet. The law of regulation and the performance variation under different conditions are obtained by wind tunnel test. The flow coefficient increases first but then decreases with the increase in the inlet opening, and the pressure rise ratio and total pressure recovery coefficient increase first and then decrease with the increase in the mass flow rate. In general, under the condition of a high Mach number (Ma > 0.4), the inlet opening of this test configuration should not exceed 50%. The deflectors can maintain the normal work of the environmental control system by moving properly to control the mass flow rate of the auxiliary inlet. [ABSTRACT FROM AUTHOR]

In this study, an experimental investigation is performed on a scaled, all-movable horizontal tail to study the aeroelastic behaviors induced by multiple free-plays. The dynamic response in wind tunnel tests is measured by strain gauges, an accelerometer, and a binocular vision measurement system. The obtained results indicate that the present aeroelastic system exhibits highly nonlinear characteristics and undergoes two independent limit cycle oscillations (LCOs) induced by bending free-play and torsion free-play, respectively. Further, various parametric studies are conducted to evaluate the effects of the free-play angles, angle of attack, flow velocity, and gust excitation on the LCOs. It is found that the value of free-play angle has no significant effect on the critical flow velocity which leads to the occurrence of LCOs. The amplitude and frequency of LCOs increase with the increasing free-play angle and flow velocity. Moreover, the horizontal tail experiences high-order harmonic resonances when LCOs appear. Finally, the stability of limit cycles is analyzed based on the gust excitation experiment. Overall, compared to an all-movable horizontal tail with single free-play, the multiple free-plays system exhibits more complex dynamic behaviors. In this paper, the measured results of the scaled model, which has a similar mass distribution and stiffness distribution as actual aircraft, may be valuable for predicting such LCOs induced by multiple free-plays, and providing a reference for the design of all-movable horizontal tail to prevent LCOs. [ABSTRACT FROM AUTHOR]

Icing is a common phenomenon in nature and has a serious impact on wind turbines. Anti-icing coatings have become a major focus of industrial applications and academic research. In this study, a hydrophobic nano-carbon coating was prepared from corn-straw-biogas residue. The characterization results of the SEM, BET, FTIR, and XRD analyses showed that the hydrophobic nano-carbon has good pore structure and crystal structure. The hydrophobic and anti-icing effects of the carbon were confirmed by contact-angle measurements and anti-icing experiments. The ice thicknesses of the hydrophobic nano-carbon-coated aluminum-alloy blade (AAB) and bakelite blade (BB) were found to decrease by 1.20 mm and 1.10 mm, respectively, compared with those without coating; their weights decreased by 2.00 g and 1.31 g, respectively. The ratios of the icing areas before and after the hydrophobic nano-carbon coating of the AAB and BB were 8.15% and 9.65%, respectively. In brief, this method is a more effective technique for creating anti-icing coatings on wind-turbine blades and other outdoor apparatus. [ABSTRACT FROM AUTHOR]

In cold areas, wind turbines face ice risk. The ice accretion on the blade surface will reduce the output power of wind turbines. To explore the effect of blade material on icing distribution, the blades of aluminum and carbon fiber-reinforced polymer (CFRP) were made, and the icing wind tunnel tests were carried out. The icing test is conducted under three icing times (2 min, 4 min, and 6 min) and three ambient temperatures (−5 °C, −10 °C, and −15 °C). The experimental results show that the icing time and ambient temperature are key factors in icing distribution. When the icing time increases, the average thickness of ice on the blade surface increases, and the airfoil profile of the blade changes significantly. When the ambient temperature decreases, the average thickness of ice on the blade surface increases, and the ice type changes from glaze ice to rime ice. The effect of blade material on the icing distribution is significantly affected by ambient temperature. [ABSTRACT FROM AUTHOR]

The significance of long-span bridges being susceptible to wind-induced vibrations and the need for evaluating their aerodynamic performance is the focus of this study. The main emphasis is on experimental methods for assessing the bridges' aerodynamic stability, using sectional model tests with the free vibration technique. The dynamic properties of the model are determined from the measured response, using various system identification methods, including the modified Ibrahim time domain (MITD) and iterative least squares (ILS) for two-degree-of-freedom systems and the logarithmic decrement method (LDM) and the Hilbert transform method (HTM) for single-degree-of-freedom (SDOF) systems. A new dynamic testing setup was designed to facilitate single-degree-of-freedom (heave and pitch) and coupled two-degree-of-freedom (2DOF) motion in a wind tunnel section model. The vertical and torsional stiffnesses of the model were adjusted with elastic springs. A Great Belt Bridge section model was selected for testing due to its streamlined aerodynamic shape. The direct and crossflow derivatives were extracted from the measured response using the system identification methods mentioned. Additionally, analytical studies and numerical computational fluid dynamics simulations were conducted to validate the experimental results. The study found that HTM is most effective in SDOF due to its ability to extract both damping and frequency from the nonlinear response, whereas the MITD method is faster in converging system parameters in 2DOF system tests. The experimental and numerical results are comparable to the flat plate, which confirms the streamlined behavior of the Great Belt section from an aerodynamic perspective. [ABSTRACT FROM AUTHOR]

Existing studies have found that curved beam unilateral stayed bridges (CBUSB) have a risk of cable breakage under the design wind velocity. To ensure structural wind-induced vibration security, it is necessary to study the wind-induced vibration characteristics of CBUSBs considering the influence of the impact load due to the cable breakage. Based on the aerodynamic coefficients determined by a wind tunnel test and the established impact load model, parametric analyses of important CBUSBs' characteristics (beam curvature and cable arrangement scheme) and the location of the cable breakage are carried out to assess the influence of cable breakage on the time-domain statistical values and frequency-domain distribution characteristics of wind-induced vibration response. The DAF, considering the influence of cable breakages on the wind-induced vibration peak value of CBUSBs, is proposed through dynamic analysis. Study results show that, with increasing curvature, under the two-modes action of wind loads and impact loads, the fluctuation component of the CBUSB is changed, resulting in a smaller proportion of resonant response. For CBUSBs with unilateral or bilateral cable arrangements, their wind-induced vibration behavior is significantly different. The former have dynamic characteristics and the latter have quasi-static characteristics. The breakage of the shortest cable at 7/33 to 7/22 of the curved beam length and its symmetry part significantly increases the wind-induced peak response of CBUSBs. The DAF recommended values can consider the amplification effect of wind-induced vibration due to the cable breakage. [ABSTRACT FROM AUTHOR]

Wind turbines operating in cold regions are prone to blade icing, which seriously affects their aerodynamic characteristics and safety performance. Coatings are one of the effective solutions to the icing problem on wind turbine blades. In this study, MoS2/ZnO/PDMS superhydrophobic nano-anti-icing coatings were prepared using the hydrothermal method and the liquid phase method. SEM revealed that the MoS2/ZnO coating was a typical superhydrophobic nanostructure with an ultra-thin sheet-like morphology of clusters and a hilly nano-rough structure, with contact angles (CA) of 152.1° and 4.7° with water droplets and the sliding angle (SA), respectively. The MoS2/ZnO/PDMS coating had an adhesion strength to ice of 78 kPa, which was 60.2% lower than an uncoated surface. The icing effects of the NACA0018 airfoil blade model with or without MoS2/ZnO coatings were studied at different ambient temperatures and wind speeds using the icing wind tunnel test. The results showed that, compared to uncoated blades, the level of icing was lower on the blade airfoil surface that was coated with MoS2/ZnO. At 10 m/s and −10 °C, the icing thickness and icing area of the leading edge of the blade airfoil were 13.7% and 28.3% lower, respectively. This study provides a valuable reference for the development of anti-icing coatings for wind turbine blades. [ABSTRACT FROM AUTHOR]

Multiple unusual vibrations occurred in SEG Plaza from May 18 to 20, 2021. To investigate the causes of these vibrations, a rigidity compression wind tunnel test was applied to study the wind-induced response of the main structure, and acceleration sensitivity analysis was conducted with parameters such as wind speed, structural period and damping ratio included. Additionally, the mast vortex-induced resonance equivalent force of reaction in the bottom was exerted on the top of the structure to obtain the acceleration response of the main structure with mast. Based on the evaluation of the vibration response of the structure before and after considering the mast as per the current specifications, it is indicated that the base overturning moment of the structure is much smaller than the specification value excluding the factor of mast, and the acceleration response varies significantly with wind pressure, structural frequency and damping ratio, but the centroid acceleration and the angular acceleration meet the comfort requirements. This indicates that the wind load on the main structure is not the dominant cause of the structural vibration. With the mast taken into account, the acceleration response of the structure exceeds the limits of the comfort level to varying degrees. For a mast damping ratio of 0.3%, the maximum angular acceleration exceeds the H-90 limit and the comfort level is poor. These findings provide considerable evidence that the dominant cause of vibration in the SEG Plaza was the vortex resonance of the top mast inducing higher mode resonance in the main structure. [ABSTRACT FROM AUTHOR]

New knowledge in multidisciplinary methodology is presented in this article for the design, aerodynamic optimization, and model validation of an adaptive wing prototype. The optimization framework integrates the design, the finite element analysis, and the model validation. A computational fluid dynamics model of the adaptive wing and the flow in its vicinity was developed and validated with experimental metrics, such as the lift, the drag, and the lift-to-drag ratio. A new genetic algorithm strategy was chosen to find the optimized airfoil shapes for the prototype's upper surface. The reliability of the proposed methodology was investigated through the design, manufacture, and testing of a wing prototype proposed for the UAV S45. The experimental and simulated results have shown a low drag production and a high lift-to-drag ratio of the adaptive wing prototype that will translate into a reduction in fuel consumption and an increase in cruising flight range and therefore into climate improvement. [ABSTRACT FROM AUTHOR]

In order to simulate the flight state of the helicopter effectively, it is necessary to trim the helicopter during the forward flight in a wind tunnel test. Previously, due to the lack of an internal-control closed loop in the test rig, the helicopter-wind-tunnel-test trimming was carried out manually, with low test efficiency, unstable data quality, and high labor intensity. With the continuous development of computer technology and automatic control technology, the helicopter-wind-tunnel-test trimming technology has been developing in the direction of automation and intelligence. The helicopter wind tunnel test automatic trimming system is a typical multi-input–multi-output (MIMO), strongly coupled, and complex nonlinear system, involving data acquisition and a processing system, rotor control system, tail-supported mechanism control system, wind-tunnel-speed pressure control system, and other subsystems, which is difficult to describe with an accurate mathematical model. Therefore, in order to meet the needs of a 3 m diameter rotor model aerodynamic performance evaluation and noise characteristics research wind tunnel test, an error feedback variable step automatic trimming algorithm is proposed based on the fuzzy-control principle to realize automatic trimming of aerodynamic loads of rotor model in the forward flight state. To verify the effectiveness and reliability of the trimming strategy, a series of wind tunnel tests on a 3 m diameter scaled rotor model of a helicopter were conducted in the FL-17 aeroacoustics wind tunnel of China Aerodynamics Research and Development Center (CARDC) based on the Φ3m tail-supported helicopter rotor model wind tunnel test rig. The wind tunnel test's results show that the proposed automatic trimming algorithm has the characteristics of fast trimming speed and high efficiency, which can realize the automatic trimming of rotor model aerodynamic loads under different test states in the wind tunnel test effectively and reliably and greatly improve the intelligence level of helicopter wind tunnel test. [ABSTRACT FROM AUTHOR]

Feedforward gust alleviation control using gusts as input signals has received increasing attention in recent years. One of the most important issues in such a control scheme is how to obtain the high-quality gust information during an aircraft's flight. In this study, a calculation method for obtaining gust information when an aircraft is flying with an arbitrary attitude is derived, based on which a simplified calculation method is established. A wind tunnel test was carried out to verify the gust calculation method. Numerical simulations were employed to investigate the influence of sensor characteristics on the gust calculation accuracy and gust alleviation performance. The results show that the time delay of the sensor has a very important influence and leads to decreases in the gust calculation accuracy and the alleviation effect. A five-hole probe was mounted on an aircraft model for gust sensing, and a gust alleviation wind tunnel test was conducted by combining the gust calculation with the feedforward gust alleviation system. The accurate calculation of the gust signal enables the feedforward gust alleviation system to achieve a 39.12% reduction of wing root bending moment and a 65.47% reduction of wingtip acceleration on average. [ABSTRACT FROM AUTHOR]

Major disasters and losses would be caused by the galloping of transmission lines. The basis for studying the galloping mechanism of transmission lines is to analyze the aerodynamic characteristics of iced conductors. The wind tunnel test is a traditional way to obtain the aerodynamic coefficients of an iced transmission line under wind load. Due to the high cost and long duration of wind tunnel tests, an experimental method based on machine learning to predict aerodynamic coefficients is proposed. Here, the steady and unsteady aerodynamic coefficients of an iced conductor under different parameters were obtained by wind tunnel test, and then the aerodynamic coefficients of the iced conductor under different parameters were predicted by machine learning. The aerodynamic coefficients of each iced conductor varied with the angle of wind attack by the wind tunnel test. The Den Hartog and Nigol coefficients determined based on the aerodynamic coefficients obtained by machine learning and wind tunnel test are in agreement. The results show the feasibility of the machine learning prediction method. [ABSTRACT FROM AUTHOR]