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Accurate wind pressure analysis on high‐rise buildings is critical for wind load prediction. However, traditional methods struggle with the inherent complexity and multiscale nature of these data. Furthermore, the high cost and practical limitations of deploying extensive sensor networks restrict the data collection capabilities. This study addresses these limitations by introducing a novel framework for optimal sensor placement on high‐rise buildings. The framework leverages the strengths of multiresolution dynamic mode decomposition (mrDMD) for feature extraction and incorporates a novel regularization term within an existing sensor placement algorithm under constraints. This innovative term enables the algorithm to consider real‐world system constraints during sensor selection, leading to a more practical and efficient solution for wind pressure analysis. mrDMD effectively analyzes the multiscale features of wind pressure data. The extracted mrDMD modes, combined with the enhanced constrained QR decomposition technique, guide the selection of informative sensor locations. This approach minimizes the required number of sensors while ensuring accurate pressure field reconstruction and adhering to real‐world placement constraints. The effectiveness of this method is validated using data from a scaled building model tested in a wind tunnel. This approach has the potential to revolutionize wind pressure analysis for high‐rise buildings, paving the way for advancements in digital twins, real‐time monitoring, and risk assessment of wind loads. [ABSTRACT FROM AUTHOR]

Understanding the aerodynamic performance of scaled-down models is vital for providing crucial insights into wind energy optimization. In this study, the aerodynamic performance of a scaled-down model (12%) was investigated. This validates the findings of the unsteady aerodynamic experiment (UAE) test sequence H. UAE tests provide information on the configuration and conditions of wind tunnel testing to measure the pressure coefficient distribution on the blade surface and the aerodynamic performance of the wind turbine. The computational simulations used shear stress transport and kinetic energy (SST K-Omega) and transitional shear stress transport (SST) turbulence models, with wind speeds ranging from 5 m/s to 25 m/s for the National Renewable Energy Laboratory (NREL) Phase VI and 4 m/s to 14 m/s for the 12% scaled-down model. The aerodynamic performance of both cases was assessed at representative wind speeds of 7 m/s for low, 10 m/s for medium, and 20 m/s for high flow speeds for NREL Phase VI and 7 m/s for low, 9 m/s medium, and 12 m/s for the scaled-down model. The results of the SST K-Omega and transitional SST models were aligned with experimental test measurement data at low wind speeds. However, the SST K-Omega torque values exhibited a slight deviation. The transitional SST and SST K-Omega models yielded aerodynamic properties that were comparable to those of the 12% scaled-down model. The torque values obtained from the simulation for the full-scale NREL Phase VI and the scaled-down model were 1686.5 Nm and 0.8349 Nm, respectively. Both turbulence models reliably predicted torque and pressure coefficient values that were consistent with the experimental data, considering specific flow regimes. The pressure coefficient was maximum at the leading edge of the wind turbine blade on the windward side and minimum on the leeward side. For the 12% scaled-down model, the flow simulation results bordering the low-pressure region of the blade varied slightly. [ABSTRACT FROM AUTHOR]

This article aims to present the results of tunnel tests and field tests of small-scale horizontal-axis wind turbines. The article proposes a new concept of turbine rotor adapted to improve efficiency at low wind speeds. The methodology for calculating the rotor and generator is shown. The turbine construction solution is presented briefly, along with the technology for manufacturing turbine components and assembly. An analysis of the obtained results is also conducted. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this paper is to reshape a fast-jet electronics pod's external geometry to ensure compliance with aircraft pylon load limits across its carriage envelope while adhering to onboard system constraints and fitment specifications. Design/methodology/approach: Initial geometric layout determination used empirical methods. Performance approximation on the aircraft with added fairings and stabilising fin configurations was conducted using a panel code. Verification of loads was done using a full steady Reynolds-averaged Navier–Stokes solver, validated against published wind tunnel test data. Acceptable load envelope for the aircraft pylon was defined using two already-certified stores with known flight envelopes. Findings: Re-lofting the pod's geometry enabled meeting all geometric and pylon load constraints. However, due to the pod's large size, re-lofting alone was not adequate to respect aircraft/pylon load limitations. A flight restriction was imposed on the aircraft's roll rate to reduce yaw and roll moments within allowable limits. Practical implications: The geometry of an electronics pod was redesigned to maximise the permissible flight envelope on its carriage aircraft while respecting the safe carriage load limits determined for its store pylon. Aircraft carriage load constraints must be determined upfront when considering the design of fast-jet electronic pods. Originality/value: A process for determining the unknown load constraints of a carriage aircraft by analogy is presented, along with the process of tailoring the geometry of an electronics pod to respect aerodynamic load and geometric constraints. [ABSTRACT FROM AUTHOR]

Separated shear layer roll-up over the airfoil suction surface at post-stall incidences leads to harmonic vortex shedding and may damage the body structure if the shedding frequency gets locked into one of the natural frequencies of the body. This article presents the results of a series of wind tunnel tests carried out on a stationary and oscillatory NACA4412 airfoil at an angle of attack (AOA) of 45° and Reynolds numbers Re=1.34×105 and Re=1.52×105 to perform an in-depth investigation of the vortex shedding and lock-in region for an oscillating airfoil in the low subsonic flow regime. Resulting from the semisinusoidal forced pitching motion, the lock-in region in the oscillation's frequency-amplitude plane was V-shaped, where the vortices shed with the oscillation frequency (lock-in condition) inside the V boundaries. Outside the V boundaries (unlocked conditions), the random shedding of vortices and their interaction causes the kinetic energy scattering in the frequency band limited to the oscillation frequency and the frequency associated with the quasi-steady condition due to the mean angle of attack. Moreover, the aerodynamic damping was examined by calculating the net energy transfer between the body and flow indicated that the direction of the energy transfer between the airfoil's body and flow is a function of both the oscillation amplitude and frequency, except during oscillation with the resonant frequency at which energy is always transferred from flow to the body. [ABSTRACT FROM AUTHOR]

The vortex-induced vibration (VIV) problem has been of critical concern for the wind-resistance of long-span bridges. Usually there are four types of approach for VIV studies: wind tunnel tests, field monitoring, computational fluid dynamics and mathematical models. However, traditional approaches have shown some limitations, such as high cost and low efficiency. In order to improve the efficiency and accuracy of VIV studies, this article has taken the VIV problem of a split three-box girder in a cable-stayed and cooperative suspension system bridge as an instance, and conducted a series of VIV wind tunnel tests. An approach based on machine learning is described that is able to serve as a complement to the wind tunnel tests. The proposed approach involves two steps: firstly, based on the dataset produced by wind tunnel tests, a clustering algorithm is introduced to separate the VIV signals automatically from other vibrations. Then, an artificial neural network is utilized to recognize the VIV response and aerodynamic force in the lock-in region directly. It is shown that the clustering algorithm can be a good tool for the recognition of VIV signals. Moreover, the proposed artificial neural network models show good ability for recognizing VIV amplitude and aerodynamic lift force. [ABSTRACT FROM AUTHOR]

Under the action of the fluctuating wind load, the low frequency part produces background response to the structures, while the high frequency part produces resonance response to the structures. In structural design, equivalent static wind load is usually used to equate the fluctuating wind load. Although there are various methods of evaluating the equivalent static wind load, they did not consider the correlation between modal responses or considered them insufficiently. Therefore, in this paper, the correlation between modal response is considered to evaluate the equivalent static wind load, the displacement response is decomposed by proper orthogonal decomposition (POD) method, the correlation between modal displacement is removed, the equivalent static wind load is expressed in the form of displacement mode, and then the correlation between modal response is fully considered in the extreme value combination. This paper combines the equivalent static wind loads in order to make the wind resistance design more reasonable for high‐rise buildings. First, the formulas of equivalent static wind loads expressed by displacement modes of background and resonant response are deduced based on modal decomposition and POD method. Second, the combination formulas of square‐root‐of‐sum‐square (SRSS) and complete‐quadratic‐combination (CQC) rules for the equivalent static wind loads considering the mean wind loads are proposed. Both the linear combination formula of SRSS for the equivalent static wind load and the weighting factor expressions of background and resonance equivalent static wind load are given. Third, the accuracy and validity of the formulas of equivalent static wind load are verified by a wind tunnel pressure test of a high‐rise building. Finally, the simplified combination coefficient formulas for the equivalent static wind loads are proposed, and the combination of the high‐rise building base's fluctuating equivalent static wind loads of along‐wind direction, across‐wind direction, and torsional direction is analyzed. [ABSTRACT FROM AUTHOR]

Computational fluid dynamic (CFD) has not been widely accepted as a design tool in current wind‐resistant structural design practices due to its contentious accuracy. To promote the application of CFD in wind‐resistant structural design, the accuracy of CFD should be comprehensively validated. However, most previous validation studies were focused on isolated generic or regular‐shaped buildings. This paper evaluates the accuracy of large eddy simulation (LES) in predicting the wind loads on a 600‐m‐high supertall building with a complex appearance in a realistic urban area against wind tunnel test results. The aerodynamic characteristics obtained from the LES and the wind tunnel test are compared and analyzed in detail, including wind pressure and force coefficients, wind force spectra, base moments, and correlations of the wind loads. This study aims to assess the performance and potential as well as the strengths and weaknesses of CFD in predicting wind loads on high‐rise buildings in an urban environment and promote its application to the wind‐resistant design of skyscrapers. [ABSTRACT FROM AUTHOR]

Accurately simulating turbulent wind fields is a significant challenge in wind engineering. This study proposes a novel block‐vorticity method aimed at overcoming the limitations of traditional turbulence generation methods. By superimposing a blocked vortex field at the inlet boundary of large eddy simulation (LES), the proposed method enables the generation of highly precise and anisotropic turbulent wind fields. To validate the effectiveness of the proposed method, the study investigates wind pressures on a high‐rise building structure and performs a comparative analysis with LES narrowband synthesis random flow generator (NSRFG), traditional LES, and SST k‐ω turbulence inlet models. The results demonstrate that the proposed method can effectively simulate turbulence characteristics of atmospheric boundary layer flow, including vortex structure and stochastic fluctuating wind field. Compared to traditional methods, the wind field characteristics of turbulence intensity, instantaneous vorticity, and turbulence self‐equilibrium had obvious advantages over traditional methods. Moreover, the LES vortex method is more accurate in simulating the mean wind pressure and fluctuating wind pressure of the high‐rise building compared to traditional models and is closer to the wind tunnel test results. The proposed method provides an effective approach for generating turbulent wind fields with anisotropic characteristics and can be used to predict the wind‐induced response of civil engineering structures. [ABSTRACT FROM AUTHOR]

Due to the influence of the three-dimensional (3D) effect, the identification accuracy of 3D aerodynamic admittance functions (AAFs) would inevitably be influenced by the ratio of turbulent integral scale to model dimension (dimensionless integral scale). For this, the two-dimensional (2D) AAFs of a streamlined bridge deck in different turbulent flow fields are experimentally investigated, wherein the 2D AAF is determined by separating out the 3D effect from the 3D AAF. Consistent with the previous studies, the 3D AAFs exhibit significant flow field dependence, and are less than the Sears function in low-frequency range. Different from the 3D AAF, the 2D AAFs obtained in two turbulent flow fields are higher than the Sears function and have a good consistency in various turbulent flows. It can be therefore considered that the identification accuracy of 2D AAF of a streamlined bridge deck is not related to the dimensionless integral scale, which might avoid the possible deviation caused by the mismatch of integral scale in the wind tunnel test. An empirical formula for the 2D AAF of a streamlined bridge deck is then proposed by fitting the experimental data. In addition, to further examine the validity of above conclusion, a comparison between the 3D AAFs of a streamlined bridge deck measured in other wind tunnel tests and the predictions calculated with the present 2D AAF is also made. [ABSTRACT FROM AUTHOR]

With the increased usage of air filtration and deodorization devices in livestock houses, the demand of agricultural axial flow fans with higher pressure has been raised. To improve the aerodynamic performance of an agricultural axial fan and expand its operating range, a new axial fan was developed using the theory of variable circulation method design via wind tunnel experiments and numerical simulations. The purpose is to change the structural form at the hub of the existing blade to improve the internal flow pattern of the agricultural axial fan, so as to achieve the purpose of improving the aerodynamic performance of the agricultural axial fan and expanding the range of stable operation. In this paper, a new agricultural axial flow fan is designed using the variable circulation method with 0.91m agricultural axial flow fan size and target airflow as design parameters. Secondly, the structural parameters at the hub of the axial fan are optimized by combining the simulation results of the flow field of the designed fan. Factors such as hub diameter d, the placement angle α and the number of moving blades n are analyzed individually, revealing the basic law of the influence of the changes of these factors on the performance of the fan, and the influence of the changes of each factor on the internal flow field of the fan is observed in combination with post-processing. using the better intervals for each factor derived from the one-factor optimisation results, the ventilation volume Q and the energy efficiency ratio N were selected as response values, and a response surface simulation study was carried out for the hub diameter d, the placement angle α, and the number of moving blades n. The response surface simulation study was carried out for the hub diameter d, the placement angle α, and the number of moving blades n. The response surface functional equations were obtained and the better parameter combinations were determined. The correctness of the functional model is further verified by observing the flow field characteristics and external characteristics through post-processing. Finally, the optimised impeller was fabricated by 3D printing technology and wind tunnel tests were conducted, and the results of the actual tests further confirmed the accuracy of the optimisation results. The numerical simulation results of the study show that the optimum combination of these parameters is d=260 mm, α=-0.369°, and n=4 pieces. Experimental test results show that the optimized axial fan performance is better than initial axial fans. On the high-pressure level (120 Pa), the ventilation volume Q of agricultural axial fan increased by 163%, and the energy efficiency ratio N increased by 18.9%. This study proves the feasibility of the variable circulation method in the design of high-pressure agricultural axial flow fan, and the optimization of structural parameters can further reduce the internal vorticity of the fan. The optimized axial fan reduced the secondary flow in the internal flow field, increased the work capacity of the blades, and improved the aerodynamic performance of the fan, ensuring that the axial fan can achieve air circulation and regulation more efficiently in agricultural applications. [ABSTRACT FROM AUTHOR]

This study is inspired by an experimental observation for vortex-induced vibrations (VIVs) of a double-hanger cable system, in which a smaller vibration of the downwind hanger cable is re-excited over a narrow range of wind speeds beyond the "lock-in" range. This phenomenon is known as the wake vortex-induced vibrations (WVIVs), where the upstream wake flow induces downstream vibrations. To further investigate the characteristics and reasons for WVIVs, a refined wind tunnel test of double-hanger cable was conducted to consider the influence of aerodynamic interaction. The double-hanger cable was modeled by the tandem-arranged spring-mounted cylinders vibrating in two dimensions. The vibration responses of hanger cables were obtained under various wind speeds to reproduce the lock-in phenomenon. In addition, the vibration trajectory, phase relationship, damping ratio, inter-cable correlation, and the wind pressure on the surface of cables were analyzed. Finally, the Stockbridge dampers were designed to suppress the vibrations. The results show that under the aerodynamic interaction of the cables, the onset wind speed of VIVs in the double cables increases, and the downstream cable WVIVs closely follow the VIVs. During the WVIV phase, the downstream cable behavior is characterized by increased negative aerodynamic damping and an inverse displacement correlation between the cables. The phase relationships between the cables are time-varying due to the aerodynamic interaction. The first proper orthogonal decomposition mode of wind pressure dominates the cross-wind of motions and is crucial in vibrations. Stockbridge dampers can effectively reduce the amplitude of VIVs and eliminate WVIVs in cables. [ABSTRACT FROM AUTHOR]

This paper presents an investigation aimed at enhancing the snow resistance of bogies in a three-car grouped alpine high-speed train (HST) that operates in a snowy region. The study employs a combination of the unsteady Reynolds-averaged Navier–Stokes model, coupled with the discrete phase model. This modeling approach has been validated through wind tunnel tests, including flow field tests, two-phase flow tests, and snow-ice tests. The study comprehensively compares the characteristics of the wind-snow flow, spatial snow concentration, and the distribution of snow on the train's underbody between two scenarios: the original train's underbody structure and the multifactor collaborative optimization scheme (MCOS). The results indicate that the MCOS case facilitates the escape of snow particles from the bogie cavities by weakening the upward and reverse flows. Furthermore, the MCOS case significantly reduces the concentration of snow particles around the heat-producing elements and decreases the accumulation of snow on both the lower and upper surfaces of the bogies. As a result, it reduces snow accumulation on the bogies by 50.6%, 56.4%, 60.8%, and 62.4% at train speeds of 200, 250, 300, and 350 km/h, respectively. In summary, this research provides valuable insights for improving the snow resistance of HSTs operating in snowy regions, with potential applications in enhancing railway transportation safety and efficiency. [ABSTRACT FROM AUTHOR]

This study experimentally investigates the impact of a pair of vertical-axis wind turbines at the leading corners of a tall building on its aerodynamic characteristics. These wind turbines have the potential to serve dual purposes: harnessing wind energy under normal wind conditions and mitigating wind loading of the building under strong wind conditions. The wind tunnel testing results in this study indicate when the tip speed ratio of the turbines is 0.34, with the wind turbines rotating toward downstream, the standard deviation of lift coefficient of the building decreases by 30.9%. Meanwhile, the mean pressure coefficient and the standard deviation of pressure coefficient on both the side face and leeward face of the building also exhibit a certain degree of reduction. The peak value of the power spectral density of lift coefficient of the building is also significantly decreased. This study clearly demonstrates that the wind turbines at the leading corners of tall buildings have the potential to effectively reduce wind loading of the buildings. [ABSTRACT FROM AUTHOR]

The study investigates flutter boundaries and auto-regressive moving average model (ARMA) stability analysis through numerical simulation cases. Two wind tunnel flutter tests were conducted to analyze the influence of parameter identification errors on boundary prediction accuracy. The research findings indicate: (a) Damping errors have smaller impact than frequency errors on the criterion of flutter boundaries. The criterion in the flutter boundary method is more insensitive to damping errors than the criterion in the ARMA stability analysis method. (b) For wing bending-torsion coupled mode flutter, the criteria of these two methods exhibit similar decreasing trend, which helps to predict flutter boundaries in advance. (c) For planar bending flutter, the ARMA stability analysis method may be more suitable than the flutter boundary method. [ABSTRACT FROM AUTHOR]

Icing is a popular research area in wind energy, and the icing problem of the supercooled droplet–ice crystal mixed-phase condition is one of the new challenges. A numerical method for analyzing the icing characteristics of wind turbine airfoil under mixed-phase conditions is presented. The control equations for the dynamics of supercooled droplets and ice crystals are formulated using the Lagrangian method. Equations for the conservation of mass and energy during the icing process involving supercooled droplets and ice crystals are constructed. The impact of erosion phenomena on the mixed-phase icing process is examined, and methodologies for solving the control equations are introduced. The numerical method is utilized for modeling mixed-phase icing under a range of conditions. The results of these simulations are then compared with data obtained from icing wind tunnel tests to assess the validity of the method. The influence of various mixed-phase conditions on ice shapes is studied. It is found that higher icing temperatures correspond to a larger icing range and amount. The increase in supercooled droplet content, ice crystal content, and ice crystal diameter all contribute to enhanced ice accretion. However, the effects of ice crystal content and diameter are relatively minor. [ABSTRACT FROM AUTHOR]

Studies on aerodynamic controls of central-slotted box decks primarily focused on mitigating vortex-induced vibrations (VIV), as this type of deck typically performs well against flutter instability. However, as the span length increases, the critical wind speed of aerodynamic static instability (U cr ) might be lower than flutter critical wind speed. Thus, U cr will determine the overall aerodynamic performance of such bridges. Investigating this instability through wind tunnel testing methods and numerical simulation can be expensive and time-consuming. In this paper, surrogate models using machine learning approaches, specifically artificial neural network (ANN) and extreme gradient boosting (XGBoost), were developed and optimized for fast and reliable prediction for U cr based on wind tunnel tests and simulation data. The results demonstrated that the built surrogate models can predict U cr accurately. The parametric study results showed that the height ratio of wind fairing apex (a/b), wind angle of attack (α), and length of the main span (L) have the most influence on the U cr compared with other parameters. Finally, based on the developed ANN surrogate model and the artificial bee colony (ABC) optimization algorithm, an optimized section was proposed to enhance the section's performance against aerodynamic static instability. [ABSTRACT FROM AUTHOR]

To address the challenges in predicting the aeroelastic phenomenon and the resulting wind-induced forces on slender bridges, a real-time aeroelastic hybrid simulation (RTAHS) system was developed. The RTAHS system directly measures the aerodynamic and aeroelastic forces through load cells. It controls the next step's position of the deck section model with linear motors by solving the governing equations of motion in real time. Given the complex shape of a bridge deck section geometry, load cells are chosen for force measurement instead of as pressure sensors. In the previous RTAHS system proposed by the authors, the inertial forces of a rectangular section model were eliminated from the measured forces under the assumption of the model's rigid-body motion. However, when conducting RTAHS experiments with a realistic bridge deck section model, increasing the mass ratio between the mass of the model and the target mass input to the hybrid system results in unstable vibrations. This instability is primarily attributed to forces generated by the model's flexibility. This study developed an improved RTAHS system, which took into account the inertial forces arising from the nonrigid motion of the flexible bridge deck section model. An accelerometer was additionally installed at the midpoint of the model, and the inertial forces caused by the nonrigid behavior were compensated using a calibration factor derived from impact hammer tests. This approach was validated by comparing the spring-supported experiments conducted on a realistic bridge deck section model. [ABSTRACT FROM AUTHOR]

Saddle-shaped roofs are one typical kind of large span roofs, but there are few studies on the equivalent static wind load (ESWL) of saddle-shaped roofs, which is important for structural design. This study conducts wind pressure measurements of saddle-shaped roofs with three typical rise-span ratios (f/S=1/6 , 1/8 , 1/12) by wind tunnel tests. Subsequently, the influences of wind and structural parameters on dynamic responses and ESWLs are investigated for 81 single-layer saddle-shaped shells with different structural stiffness, including rise-span ratio, span length, roof mass, and incoming mean wind velocity. The results show that the most unfavorable wind directions of the peak structural responses for single-layer saddle-shaped shells are 60° and 90°, as well as the axisymmetric wind directions corresponding to these two wind directions, i.e., 120°, 240°, 270°, 300°. Finally, a simple fundamental vector is proposed to express the multitarget ESWLs for single-layer saddle-shaped shells to reproduce multiple peak responses at the most unfavorable wind directions. Through parametric analysis, mean pressure coefficients of roof zones are proposed. Within the investigated parameter ranges, the fluctuating ESWL coefficients are expressed as the functions of the reduced structural frequency at the most unfavorable wind directions, which is very convenient for structural engineers to determine the wind loads on main force resisting structural systems. [ABSTRACT FROM AUTHOR]

Historical wooden pagodas are found in several Asian countries and are considered priceless world heritage values due to their majestic appearance and exquisite manufacturing techniques. Over time, the structure may occur inclination due to the wind action. This study presents a nondestructive method based on trees that can reduce wind pressures and loads on the wooden pagoda. The methodology was applied to the Yingxian wooden pagoda in China, a site of great historical interest. The feasibility and effectiveness of the methodology were validated through wind tunnel tests. A refined model of the wooden pagoda, with a scale ratio of 1∶50 , was fabricated and tested. Wind pressure coefficients and shelter effects of the pagoda with and without trees were analyzed. Additionally, wind base loads and reduction rates of pagoda with various tree arrangements are calculated and discussed, and the suggested tree arrangements are proposed. Though the discussion of the study, the study shows that the proposed nondestructive method can effectively reduce wind loads and actions with an average reduction rate of 12%. The height of the trees significantly affects the shelter effect of the tree blockings. This study provides a useful reference for protecting historical pagodas with similar profiles. [ABSTRACT FROM AUTHOR]

This article reports about a wind‐tunnel experiment carried out in the ONERA F2 low‐speed wind tunnel on a model of the DU 97‐W‐300Mod airfoil designed for wind turbine application. The wind tunnel, the airfoil model, and experimental techniques used are presented, with special emphasis on the data processing and corrections required to derive airfoil forces and pressure distribution. To better document the flow physics at play, the results are illustrated by infrared thermography and surface oil flow visualization. The test allowed investigating Reynolds number effects between 1 and 3.8 millions. To ameliorate the understanding of the benefits and limitations of such airfoil testing, one section is devoted to the comparison of present results with previous experiments in other wind tunnels. Some of the difficulties arising in airfoil testing are evidenced and discussed to contribute to the improvement of test methods. [ABSTRACT FROM AUTHOR]

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A numerical analysis of the wind load for the purpose of evaluating the wind resistance acting on a ship and the validity of the wind profile applied to determine the wind load coefficient were conducted. Through the evaluation of estimation results by a wind tunnel test, CFD analysis, and present semi-empirical formulae, it was recognized that the difference in estimation of ship resistance due to wind could not be ignored. In order to identify the main causes of the difference, extensive analyses were performed for a container, tanker, and LNG carrier. In particular, the estimation results for a container ship with two islands showed unreliable results. The main reason for the difference is that each method reflects the wind speed in the vertical direction differently, and the wind profile applied when considering the self-induced wind effect is not a uniform wind profile. In the calculation of wind resistance by self-induced wind, wind resistance estimation results differed by about 1.5% to 3.4% depending on the application of uniform or non-uniform wind profile. The total wind resistance acting on the vessel shall be divided into wind resistance from a stationary vessel without speed and wind resistance caused by the forward speed of the vessel in no wind conditions. Therefore, it is reasonable to apply a uniform wind profile to estimate wind resistance caused by the ship's forward speed, while a wind profile that reflects the effect of changes in the ship's vertical speed should be applied to estimate the wind resistance caused by the ship's forward speed. [ABSTRACT FROM AUTHOR]

To investigate the nonlinear flutter characteristics of long-span suspension bridges under different deck ancillary structures and configurations, including those with and without a central wind-permeable zone, as well as to analyze the hysteresis phenomenon of a subcritical flutter and elucidate the mechanisms leading to the occurrence of nonlinear flutter, this paper studies first the post-flutter characteristics of the torsion single-degree-of-freedom (SDOF) test systems and vertical bending–torsion two-degree-of-freedom (2DOF) test systems under different aerodynamic shape conditions are further analyzed, and the role of the vertical vibration in coupled nonlinear flutter is discussed. The results indicate that better flutter performance is achieved in the absence of bridge deck auxiliary structures with a central wind-permeable zone. The participation of vertical vibrations in the post-flutter vibration increases with the increase in wind speed, reducing the flutter performance of the main girder. Furthermore, the hysteresis phenomenon in the subcritical flutter state is observed in the wind tunnel experiment, and its evolution law and mechanism are discussed from the perspective of amplitude-dependent damping. Finally, the vibration-generating mechanism of the limit oscillation ring is elaborated in terms of the evolution law of the post-flutter vibration damping. [ABSTRACT FROM AUTHOR]

Changes in canopy structures caused by harvesting and regeneration practices can significantly alter the wind environment. Therefore, it is essential to understand the wind patterns influenced by seed tree arrangements for predicting seed dispersal by winds and ensuring the success of natural regeneration. This study aimed to identify how wind speed responds to seed tree arrangement designs with differing horizontal distances, vertical positions, and free-stream wind speeds. A wind tunnel test was conducted using pine saplings for a scale model of various seed tree arrangements, and the change in wake speed was tracked. The wake's relative wind speed averaged 71%, ranging from 3.5% to 108.5%, depending on the seed tree arrangement, distance from saplings, and vertical position. It peaked within the patch of three seed trees compared to other arrangements and at the top canopy layer. The empirical function effectively described the wind speed reduction and recovery with distance from saplings. For instance, the minimum wind speed was reached at 0.6–2.2 times the canopy height, and a wind speed reduction of over 20% of the free-stream wind speed was maintained at a 1.6–7.6 canopy height. A negative relationship between the seed tree leaf area and the relative wind speed was observed only at the top canopy layer. This study presents empirical evidence on the patterns of wake winds induced by different types of heterogeneous canopy structures. [ABSTRACT FROM AUTHOR]

The Golmud-Korla Railway in the Gobi area faces operational challenges due to sand hazards, caused by strong and variable winds. This study addresses these challenges by conducting wind tunnel tests to evaluate the protective benefits of High Density Polyethylene (HDPE) board sand fences, focusing on their orientation relative to various wind directions (referred to as 'wind angle'). This study found that the size of the low-velocity zone on the leeward side of the sand fences (LSF) expanded with an increase in the wind angle (WA). At 1H (the height of the sand fence) and 2H positions on the LSF, the wind speed profiles (WSP) exhibited a segmented logarithmic growth, constrained by Z = H at varying WAs. The efficacy of the sand fence in obstructing airflow escalated as WA increased. The size of the WA has a significant impact on the protective efficiency of HDPE board sand fences. Furthermore, compared to typical sandy surfaces, the rate of sand transport across the Gobi surface diminishes more slowly with height, attributed to the gravel's rebound effect. This phenomenon allows some sand particles to bypass the fences, rendering them less effective at blocking wind and trapping sand than in sandy environments. This paper offers scientific evidence supporting the practical use and enhancement of HDPE board sand fences in varied wind conditions. [ABSTRACT FROM AUTHOR]

Rain–wind-induced vibration (RWIV) is a phenomenon of cable vibration with a large amplitude and low frequency. The RWIV involves gas, liquid, and solid phases. Therefore, it is very difficult to reproduce the RWIV by using the method of numerical simulation. In the previous research, based on the lubrication theory, researchers have established a theory model for RWIV of a rigid segment of 3D cables. Based on the previous researches, a new numerical simulation method of 3D flexible cable is proposed, which can reflect the interaction between the gas, the liquid, and the solid. The aerodynamics force is calculated by the COMSOL. The evolution of the water film is calculated by MATLAB. In the previous researches, the variation of cable shape was not considered. The cable vibration is obtained by solving the vibration equation of a 1-DOF system. In this paper, the cable is considered to generate the variation in the shape of the cable. The results of cable vibration are obtained by establishing a 3D flexible cable model in ANSYS. By using the new numerical simulation method, the RWIV phenomenon of 3D flexible cable is reproduced. The revolution of the water film, the variation of cable lift, and the cable vibration are calculated at different wind speeds. The spatial shape of cable vibration at every time is obtained. By the analysis of numerical simulation results, the mechanism of RWIV is explained again. Then, by comparing with the previous numerical simulation method, the advantage of the simulation method of RWIV of 3D flexible cable is reflected. Finally, by comparing the numerical simulation results with the results of the wind tunnel test of Gao et al., the accuracy of the simulation method of RWIV of 3D flexible cable is verified. [ABSTRACT FROM AUTHOR]

AbstractRail models may be simplified at different levels in wind tunnel tests and numerical simulations. This work used delayed detached eddy simulations to analyze and compare the aerodynamic loads (drag, side force, lift, and rolling moment), surface pressure, and flow characteristics around a train model placed on subgrades with three different rail models: no-rail, simplified rail, and realistic rail. The simulations were conducted at a large yaw angle of 60°. The mean aerodynamic characteristics of the car bodies and bogies were similar with the simplified rail model and realistic rail model, while those were completely different without the rail model. The difference in aerodynamic loads between the no-rail model and the realistic rail model was as high as 53.1%, whereas the difference between the simplified and realistic rail models was only 7.7%. And for fluctuating aerodynamic characteristics of the train, there was still differences between the cases with the simplified and realistic models. Further, the rail model significantly impacted the flow (such as the velocity, turbulent kinetic energy, and vorticity) around the train, especially under the train, resulting in significant differences in the aerodynamic loads in time and frequency domains. For accurate and precise measurements of mean aerodynamic loads, incorporating a rail model (with the simplified model being sufficient) can improve accuracy by 48.0% and precision by 66.9%. When focusing on fluctuating aerodynamic loads, using a realistic rail model is essential to accurately capture amplitude-frequency characteristics. The rail model setup recommendations outlined in this work aim to enhance the accuracy and reliability of various wind tunnel tests and numerical simulations related to train aerodynamics. [ABSTRACT FROM AUTHOR]

The wind-resistant performance of cable-stayed bridges under construction deteriorates sharply as the cantilever length increases, and the arrangement of the temporary pier is an effective measure to improve aerodynamic stability. To investigate the effect of the temporary pier on buffeting response of a long-span three-tower cable-stayed bridge under construction, the nonlinear buffeting analysis and wind tunnel test of aeroelastic model methods are adopted in this paper. The influence of the type and arrangement positions of temporary piers on mean wind response and the nonlinear buffeting response of double-cantilever construction are studied, and the arrangement of the temporary pier is optimized based on the buffeting response. The results show that the reduction rates of the RMS of the torsional moment at the tower bottom and the lateral buffeting displacement at the girder end with the rigid pier are 35.6% and 59.2% compared to those without the temporary pier. Further, the buffeting response will decrease as the distance between the rigid pier and the tower increases in the state. On the contrary, in the double-cantilever construction state before the constraint of temporary piers, the buffeting response will become significant as the distance increases. Therefore, it is necessary to consider the buffeting response under two construction states when optimizing the arrangement position of the temporary pier. [ABSTRACT FROM AUTHOR]

Wind energy has emerged as a prominent alternative energy source, harvesting energy through turbines to contribute sustainably to the electricity grid. Effective control of these turbines is crucial for regulating power generation, with wind farm control strategies geared toward maximizing on-demand energy generation. In this work, we propose a wind turbine regulator based on blade-pitch actuation and assess the impact of adopted turbine derating strategies on aerodynamic loading and downstream power availability in an experimental setting. By considering a derating strategy based on generator torque control law, we explore two wind farm control approaches: thrust balance and power compensation. Our findings highlight the advantages of balancing aerodynamic loads across the farm, preventing turbine saturation, and enhancing power availability by 3%–5% compared to a uniform power dispatch. Furthermore, the inclusion of power compensation results in a heightened upper limit in wind farm power tracking, indicating a 22% boost in wind farm power availability. This research underscores the potential benefits of innovative turbine regulation strategies for optimizing wind farm performance and enhancing overall energy flexibility. [ABSTRACT FROM AUTHOR]

Stall flutter is a serious threat to the operational integrity in turbomachinery, particularly in the final stage rotors of steam turbines and in compressors. Although computer science has developed rapidly and much of the research can be carried out using numerical tools, the simulation of some phenomena, such as stall flutter, is still very challenging and needs to be supported by experimental data. This paper presents an innovative experimental linear blade cascade design with five prismatic blades with pitch degrees of freedom, designed to be operated in a low subsonic wind tunnel. The geometry of the blade cascade was chosen on the basis of the experimental and numerical tests to allow stall flutter initiation. New suspension, measurement and electromagnetic excitation systems were developed and experimentally tested to allow accurate measurement of aerodynamic damping during controlled flutter tests. The novelty of the experimental blade cascade is the possibility of single pulse excitation of the blades. The cascade can be brought to the edge of stability by adjusting the angle of attack and flow velocity, and then the pulse can be used to induce stall flutter. Measurement of both mechanical and flow characteristics, also demonstrated in this paper, will provide data for in-depth analysis of stall flutter initiation and propagation. [ABSTRACT FROM AUTHOR]

The emergence of prosumers, who actively participate in designing and producing goods, has generated a growing interest in homemade products. Factors such as design methods, component reuse, or digital fabrication empower prosumer designers to realize their ideas. Although there are cases of bioinspired products manufactured by prosumers, the interactions between bioinspired design methods in the prosumer field have not been addressed from an academic point of view. This article presents a case that combines bioinspired design methods with prosumer characteristics from the perspective of a designer who uses biological research results whilst acting as a prosumer. The proposal is to see whether working on a small scale, without the need for biomimetics experts, and independently, as a prosumer, is feasible and valuable. As a result, a bicycle flashlight is designed with a microgenerator bioinspired by the geometry of samara seeds, and is tested in a wind tunnel. This case shows that the integration of a bioinspired design in prosumer contexts poses unique challenges and requires a multidisciplinary approach. Furthermore, the application of a bioinspired approach in this case has not only provided a certain level of novelty to the final product, but has also improved its efficiency and reduced its financial expenditure. [ABSTRACT FROM AUTHOR]

The internal to external pressure ratio in a large-span cylindrical roof building with a dominant gable opening fluctuates dramatically between 0 and 1, significantly impacted by the attenuation of internal pressure. Current theories usually assume this ratio equal to 1 and overlook the attenuation effect. This study investigates four cylindrical roof models with varying opening areas, scale ratios, and wind speeds by wind tunnel tests. It analyzes ratios of mean ( C ¯ p i / C ¯ p e ), fluctuating ( σ p i / σ p e ), and peak ( C ̂ p i / C ̂ p e ) internal to external pressure to pinpoint factors affecting the internal pressure attenuation. The results highlight that the most pronounced internal pressure attenuation is at the sideward opening. The vortex shedding around the opening is induced by the wind direction, scale ratio, and wind speed. The attenuation effect decreases with lower frequencies of periodic vortex shedding. This effect generally vanishes when the windward or leeward opening ratio (A1.5/V0) exceeds 0.57%. Empirical design formulas are proposed to predict ratios of internal to external pressure considering the attenuation effect. The inertia (CI) and loss coefficients (CL) affected by the internal pressure attenuation are analyzed to estimate the air slug inertia and damping through the opening. A governing equation, incorporating reduction coefficients ( C ¯ eddy , C ̃ eddy ) from empirical design formulas, is applied to precisely compute the attenuated internal pressure in the large-span cylindrical roof building with a dominant gable opening for engineering risk assessment. [ABSTRACT FROM AUTHOR]

The existing theories for along-wind loads on slender structures, based on the "strip assumption" overlook the three-dimensionality of turbulence. However, numerous experimental phenomena contradicting the "strip assumption" highlight the need to consider the effects of three-dimensional turbulence (3D effect). This study develops an analysis model that considers the three-dimensionality of turbulence and derives a function containing the section-shape-dependent characteristic parameters to represent the 3D effect. A method for identifying the parameters through a wind tunnel test is proposed to solve this function. The parameters for the square cross section are then identified in two different turbulence fields, revealing that the identification parameters of both cases are nearly identical. This similarity indicates that the parameters are independent of the turbulence validating the proposed theories. Finally, the 3D effect on square cross-sectional structures with different aspect ratios under various turbulence integral scales is analyzed. The results showed that as the ratio of the turbulence integral scale to the windward width of the structures increases, the 3D effect reduces, but the rate of reduction slows down. In addition, increasing the aspect ratios of structures further mitigates the 3D effect, enhancing the accuracy of the "strip assumption." These results can be a reference for evaluating the accuracy of the "strip assumption" theory for square cross-sectional high-rise buildings in atmospheric boundary layer turbulence. The proposed method can be applied to investigate the 3D effect on along-wind loads of slender structures with various cross-sectional shapes. [ABSTRACT FROM AUTHOR]

Airflow separation at the rear area of the automobile is the main source of automobile aerodynamic drag. To suppress the airflow separation, minimize the aerodynamic drag of the automobile, realize energy saving and emission reduction, a bionic drag reduction device was designed based on the dorsal fin of the orca with low drag characteristics. A numerical computation method was established to maximize the drag reduction performance of the bionic device, and the parametric modeling of the bionic drag reduction device was carried out. The design of experiments, the Kriging surrogate model, and an optimization algorithm were used to optimize the bionic drag reduction device. The validity of the optimization design was validated by the wind tunnel test. Finally, the mechanism and effectiveness of the bionic device in reducing aerodynamic drag were investigated through the comparison of flow field. The results show that the optimized bionic drag reduction device can delay the airflow separation and effectively reduce turbulence intensity of the automobile. According to the wind tunnel test, the aerodynamic drag coefficient of the optimized model is reduced by 6.16% compared with the original model. [ABSTRACT FROM AUTHOR]

The main structure of the transmission tower consists of the tower body and the cross arm, which serve as vertical support and transverse extension, respectively. Compared with the tower body, due to the difference between the transverse and longitudinal projected areas of the cross-arm, the wind load distribution of the cross-arm is more complicated and requires more in-depth research. In this paper, wind tunnel force tests under skew wind were carried out on the 1:20 scaled rigid models of the tubular and the tubular-angle combined cross-arms. The tests consider four solidity ratios (0.2, 0.3, 0.4, and 0.5) under three wind speeds and 19 yaw angles. The aerodynamic force coefficients Ci, the skewed wind load factor Kθ, the transversal and longitudinal wind load distribution factor nX and nY, and the angle α between the transversal aerodynamic force coefficient (CX) and the resultant wind force coefficient (CR) were obtained and analyzed. It was found that the wind load coefficients decrease with increasing solidity ratio. The tested drag coefficient of the tubular cross-arm is larger than the combined cross-arm under the same solidity ratio. The nX of the tubular and combined cross-arm reaches the maximum range of 0.33–0.47 and 0.22–0.23 at 30° <θ < 45° and 30° < θ < 35°, respectively. The nY curves were ordered from large to small as follows: EN 50341-1, the tested tubular cross-arm, the tested combined cross-arm, and JEC-127-1979. At 55° < θ < 65°, the difference of α and θ for the tested tubular and combined cross-arm reaches the maximum of 10°–18° and 29°–32°, respectively, indicating that the lift force cannot be ignored and the assumption α = θ is not applicable. Reasonable nonlinear fitting functions are proposed to accurately calculate the wind load of the two types of cross-arms. [ABSTRACT FROM AUTHOR]

Due to the complex nature of the built environment, urban wind flow is unpredictable and characterised by high levels of turbulence and low mean wind speed. Yet, there is a potential for harnessing urban wind power by carefully integrating wind turbines within the built environment at the optimum locations. This requires a thorough investigation of wind resources to use the suitable wind turbine technology at the correct location—thus, the need for an accurate assessment of wind resources at the proposed site. This paper reviews the commonly used wind assessment tools for the urban wind flow to identify the optimum tool to be used prior to integrating wind turbines in urban areas. In situ measurements, wind tunnel tests, and CFD simulations are analysed and reviewed through their advantages and disadvantages in assessing urban wind flows. The literature shows that CFD simulations are favoured over other most commonly used tools because the tool is relatively easier to use, more efficient in comparing alternative design solutions, and can effectively communicate data visually. The paper concludes with recommendations on best practice guidelines for using CFD simulation in assessing the wind flow within the built environment and emphasises the importance of validating CFD simulation results by other available tools to avoid any associated uncertainties. [ABSTRACT FROM AUTHOR]

Purpose: An experimental investigation of hemispherical forebody interaction effects on the drag coefficient of a D-shaped model is carried out for three-dimensional flow in the subcritical range of Reynolds number 1 × 105 ≤ Re ≤ 1.8 × 105. To study the interaction effect, hemispherical shapes of various sizes are attached to the upriver of the D-shaped bluff body model. The diameter of the hemisphere (b1) varied from 0.25 to 0.75 times the diameter of the D-shaped model (b2) and its gap from the D-shaped model (g/b2) ranged from 0.25 to 1.75 b2. Design/methodology/approach: The experiments were carried out in a low-speed open-circuit closed jet wind tunnel with test section dimensions of 1.2 × 0.9 × 1.8 m (W × H × L) capable of generating maximum velocity up to 45 m/s. The wind tunnel is equipped with a driving unit which has a 175-hp motor with three propellers controlled by a 160-kW inverter drive. Drag force is measured with an internal six-component balance with the help of the Spider 3013 E-pro data acquisition system. Findings: The wind tunnel results show that the hemispherical forebody has a diameter ratio of 0.75 with a gap ratio of 0.25, resulting in a maximum drag reduction of 67%. Research limitations/implications: The turbulence intensity of the wind tunnel is about 5.6% at a velocity of 18 m/s. The uncertainty in the velocity and the drag coefficient measurement are about ±1.5 and ±2.83 %, respectively. The maximum error in the geometric model is about ±1.33 %. ractical implications: The results from the research work are helpful in choosing the optimum spacing of road vehicles, especially truck–trailer and launch vehicle applications. Social implications: Drag reduction of road vehicle resulting less fuel consumption as well as less pollution to the environment. For instance, tractor trailer experiencing approximately 45% of aerodynamics drag is due to front part of the vehicle. The other contributors are 30% due to trailer base and 25% is due to under body flow. Nearly 65% of energy was spent to overcome the aerodynamic drag, when the vehicle is traveling at the average of 70 kmph (Seifert 2008 and Doyle 2008). Originality/value: The benefits of placing the forebody in front of the main body will have a strong influence on reducing fuel consumption. [ABSTRACT FROM AUTHOR]

Highlights Air velocity characteristics within soybean rows were monitored to inquire about potential spray droplet movement inside dense foliage. Magnitude of air velocity at high and middle canopy heights decreased with decreasing row spacing and increasing plant canopy leaf area index. The objective of this study was to characterize air velocities within a group of soybean plants under controlled conditions in a University of Tennessee biosystems engineering low-speed wind tunnel. The wind tunnel had 13 module sections that were each sized 1.22 m long, 2 m high, by 2 m wide, and was powered with a 93.25-kW motor and variable frequency drive at a mean air velocity of 1.4 m s-1. Extreme high air velocities were avoided to reduce the impact and added complexities of plant structural deflections. Wind tunnel tests were conducted with soybeans grown in pots placed in the wind tunnel with pot row spacings selected as 0.25, 0.38, and 0.51 m to vary the openness of the plant canopy. These row spacings represented narrow production practices that were perceived as difficult for spray droplets to penetrate. Soybeans were grown in pots outdoors to achieve plants that resembled the hardy structural characteristics of those in field production. Plants reached the R3 growth stage when the air velocity experiments started, and mean plant height and width were 0.51 and 0.46 m, respectively. Outdoor plant canopy leaf area index (LAI) measured at heights of 0.28 and 0.43 m for pot row spacings of 0.25, 0.38, and 0.51 m were 8.27, 6.66, and 5.59 m2 m-2 and 7.04, 6.49, and 5.01 m2 m-2, respectively. Thus, increased measurement height and increased row spacing reduced LAI values as expected. Soybean pots were placed in rows oriented along the length of the wind tunnel. Air velocity component values in the foliar canopy were the greatest for longitudinal components, followed by vertical and lateral components. A complex system of three-dimensional air velocities was observed along soybean rows of various row spacings. The soybean canopy was perceived as the root cause of wind velocity blockage resulting in mean longitudinal wind velocities ranging from -0.01 to 0.61 m s-1 depending on row spacing, location between- or in-row and measurement height. Using ambient wind to reliably and consistently aid spray penetration and droplet movement into soybeans grown under conditions with dense foliage appeared to further compound the issue of spray penetration. [ABSTRACT FROM AUTHOR]

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]

Air-delivered spraying can enhance the effective transport and uniform coverage of fog droplets into the interior of the tree crown. However, it is still unclear on the effect of the intensity of air-delivered flow on the response of a single leaf to the motion state and the microcosmic settlement of fog drop. In this study, a single leaf of a pear tree was placed under the stable air flow in the test section of the wind tunnel equipment. The wind vibration response test was carried out on the leaves of a single pear tree. Four feature points were then marked on the leaves, in order to represent the leaf morphology. Binocular high-speed cameras were used to track the feature points on the leaves. The three-dimensional spatial motion model of simulated leaves was constructed to decompose into several sub-stages for subsequent analysis. A systematic analysis was made on the spatial motion trajectory of feature points, in order to explore the effect of droplet deposition on the leaf surface. The research results were as follows. The leaves showed static stability, swing, and a large number of twisting and turning complex motions under the action of wind-driven air flow. The critical response speed of wind vibration was defined as the generation of a large number of twisting motions. Once the wind speed was lower than the critical airflow speed of wind vibration, the leaves were basically lifted at the angle position in a static and stable state. When the air velocity was greater than or equal to the critical, the dynamic stable state of the leaves was destroyed into a compound motion response state of large spatial swing, turnover, and torsion, indicating the periodic motion state of the leaves under the action of strong air. Specifically, the total travel distances of leaf tips in a space movement period were 180.61, 1140.77, and 766.33 mm, respectively, at the speed of 5, 7, and 9 m/s, and the torsion angles were 290.7°, 896.8°, and 716.2°, respectively. In the test of leaf droplet deposition, the spray droplets were deposited mainly on the side of the leaf facing the airflow direction, when the airflow velocity was lower than 5 m/s. There was also an increase in the airflow velocity. The coverage rate of droplet deposition on the front of the leaf gradually decreased from 43.2% to 10.3%. When the airflow velocity was greater than the critical wind response velocity of 5 m/s, the fog droplets were deposited on both sides of the leaves. However, the droplets were deposited mainly on the opposite side of the leaves with better hydrophilicity. The spatial pose and motion of leaves were also simulated, according to the actual coordinates in the instantaneous position of leaves under the space motion. The finding can further reveal the interaction and deposition between the air flow carrying fog droplets and the leaves in the air-driven sprayer. [ABSTRACT FROM AUTHOR]

Rocket sled test avoids boundary effects in wind tunnel test and inconvenience of flight test, which is one of the feasible options for future single-stage-to-orbit. To analyze potential safety issues during payload separation and optimize the arrangement of testing sensors, different structural layouts and operating speeds of the rocket sled are conducted based on computational fluid dynamics and computational aeroacoustics. The hypersonic winged standard model is utilized as the load for these simulations. The analysis encompasses the evolution of shock waves, the forces exerted on the payload and noise propagation. Variations in flow field and aeroacoustic characteristics of rocket sled are analysed, revealing underlying physical mechanisms. It is observed that placing the payload in front of the thruster can reduce the head pressure, excessive wingspan may have an impact on the structural safety of the wingtip, and the regions of high sound pressure levels mainly exists in the middle and rear sections of the rocket sled. Moreover, as the Mach number increases, the characteristic frequency initially rises and then declines. These researches can serve as a valuable reference for the development of ground test systems and single-stage-to-orbit. [ABSTRACT FROM AUTHOR]

High-rise structures with large aspect ratios are subjected to unexpected motions under wind excitation. Structural vibrations induced by vortices in the wake were captured by aeroelastic real-time hybrid simulation (aeroRTHS) in the companion paper. An effective and practical method is critical for explaining the mitigation of adverse wind loading impact upon these structures. Analyzing the performance of structural control devices against wind excitation in an aeroelastic wind tunnel test often is time- and cost-intensive. In this paper, aeroRTHS testing is extended to include (1) a vibration control device numerically added to the numerical substructures and tested to mitigate the cross-wind oscillation in the aeroRTHS framework; and (2) the use of 128 pressure sensors installed on two side faces of a physical building model in a boundary layer wind tunnel (BLWT) at the University of Florida Natural Hazards Engineering Research Infrastructure Equipment Facility (UF NHERI EF) to provide a more complete description of the wind-force distributions imparted on nine building configurations both with and without a tuned mass damper (TMD) at various constant wind speeds. Wind-force distribution was characterized in the time domain in terms of time histories of equivalent forces and displacements, and envelopes of wind forces. Frequency response analysis was conducted based on power spectral densities of input equivalent wind forces and output structural dynamic response. Results from the aeroRTHS tests demonstrated that the aeroRTHS method is capable of investigating aeroelastic structures with passive mitigation devices. The aeroRTHS tests in the wind tunnel demonstrated that the augmentation of buildings with TMDs is an effective way to attenuate the cross-wind vibration in tall buildings. [ABSTRACT FROM AUTHOR]

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Segregated incompressible large eddy simulation and acoustic perturbation equations were used to obtain the flow field and sound field of 1:25 scale trains with three, six and eight coaches in a long tunnel, and the aerodynamic results were verified by wind tunnel test with the same scale two-coach train model. Time-averaged drag coefficients of the head coach of three trains are similar, but at the tail coach of the multi-group trains it is much larger than that of the three-coach train. The eight-coach train presents the largest increment from the head coach to the tail coach in the standard deviation (STD) of aerodynamic force coefficients: 0.0110 for drag coefficient (Cd), 0.0198 for lift coefficient (Cl) and 0.0371 for side coefficient (Cs). Total sound pressure level at the bottom of multi-group trains presents a significant streamwise increase, which is different from the three-coach train. Tunnel walls affect the acoustic distribution at the bottom, only after the coach number reaches a certain value, and the streamwise increase in the sound pressure fluctuation of multi-group trains is strengthened by coach number. Fourier transform of the turbulent and sound pressures presents that coach number has little influence on the peak frequencies, but increases the sound pressure level values at the tail bogie cavities. Furthermore, different from the turbulent pressure, the first two sound pressure proper orthogonal decomposition (POD) modes in the bogie cavities contain 90% of the total energy, and the spatial distributions indicate that the acoustic distributions in the head and tail bogies are not related to coach number. [ABSTRACT FROM AUTHOR]

Connecting infrastructures such as steel bridges are important for sustainable and economic development of society. Understanding the risks to these infrastructures associated with wind is crucial to ensure their resilience, particularly with the evident threat of climate change. The authors will discuss the benefits of early‐stage consulting in delivering climate aware performance‐based design for steel bridges. A holistic approach comprising bridge monitoring, aerodynamic consultation coupled with wind tunnel testing and numerical simulations enables us to understand the structural response of bridges, from an aerodynamic perspective. By combining this knowledge with a local climate model, the bridge response to current and future expected wind conditions, can be predicted and assessed. The outcomes of such an approach enable us to refine design wind loads optimizing material usage and ensuring safe and cost‐effective construction processes, thereby reducing embodied carbon. [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]

The article discusses the importance of research in the field of flight dynamics, control, and simulation for advancing aeronautical sciences. It emphasizes the need for a deep understanding of flight dynamics to enhance aircraft performance, safety, and efficiency. The integration of advanced control strategies and the use of simulation play a crucial role in optimizing aircraft behavior and reducing costs. The article also provides an overview of 14 papers published in a special issue of the Aerospace journal, covering various topics such as hybrid electric propulsion, aerodynamic parameter identification, and autonomous flare control. The research presented in the papers contributes to the development of new technologies and innovations in aviation. [Extracted from the article]

The implementation of morphing wing mechanisms shows significant potential for improving aircraft performance, as highlighted in the recent literature. The Clean Sky 2 AirGreen 2 European project team is currently performing ground and wind tunnel tests to validate improvements in morphing wing structures. The project aims to demonstrate the effectiveness of these morphing designs on a full-scale flying prototype. This article describes the design methodology and structural testing of a scaled morphing-flap structure, which can adapt to three different morphing modes for various flight conditions: low-speed (take-off and landing) and high-speed (cruise). A scale factor of 1:3 was selected for the wind tunnel test campaign. Due to challenges in scaling the embedded mechanisms and actuators necessary for shape-changing, a full geometrical scale of the real flap prototype was not feasible. Static analyses were performed using the finite element method to address critical load conditions determined through three-dimensional computational fluid dynamic (CFD) analysis. The finite element (FE) analysis was conducted and the results were compared with the empirical data from the structural test. Good correlations were found between the structural testing results and numerical predictions, including static deflections and elastic deformations under applied loads. This indicates that the modeling approaches used during the design and testing phases were highly successful. Based on simulations for the ultimate load conditions tested during the wind tunnel tests, the scaled flap prototype has been deemed suitable for further testing. [ABSTRACT FROM AUTHOR]

The effect of spanwise wing non-planarity, employed in conjunction with a Gurney flap, is presented. Testing was undertaken in a low-speed wind tunnel using a rectangular wing with an aspect ratio of three. The outer one-third of the wing was non-planar, which took the form of either dihedral or a circular arc. A 2% high Gurney flap was implemented such that it could extend over the entire span or the planar inboard section. The loads were measured using a sting balance. The data show that non-planarity increases the maximum lift coefficient and the wing's lift curve slope. Gurney flap lift modulation was enhanced in the presence of non-planarity. The addition of Gurney flaps caused a greater increment in the minimum drag coefficient for the non-planar wings. The Gurney flaps reduced the lift-dependent drag of the wings. As a whole, the Gurney flaps reduced the maximum lift-to-drag ratio (L/D)max for the non-planar wings; however, the flat wing exhibited a small L/D increment with flap addition. [ABSTRACT FROM AUTHOR]