Search Results (998)

To address the severe snow accumulation within road cuttings triggered by wind-blown snow on mountainous highways, and to elucidate the influence mechanisms of cutting depth and snow fence parameters on the wind–snow flow field, this study presents a systematic investigation based on typical sections of the G577 Grade I mountain highway in the Xinjiang Uygur Autonomous Region, China. First, indoor wind tunnel experiments were conducted to observe the distribution characteristics of the wind– snow field inside and outside the cuttings and around the snow fences under varying cutting depths and fence parameters. Second, numerical simulations were performed using the Analysis System Fluent software with models identical to those used in the wind tunnel tests to analyze the airflow field and snow particle movement patterns. Finally, experimental results were compared with field observations of winter snow accumulation to validate the reliability of both the numerical simulations and wind tunnel experiments. The results indicate that under small intersection angles (15–30°), deep cuttings significantly exacerbate snowdrift accumulation trends, reducing wind speed within the cutting and increasing snow accumulation at the bottom (an increase of 31–81% per 5 m of depth). Furthermore, a nonlinear relationship regarding the impact of different snow fence parameters on flow field distribution. These findings provide theoretical support and valuable engineering references for optimizing road cutting design and snow fence construction in mountainous regions. Full article

The radial heat transfer mechanism of compacted conductors in overhead insulated cables is unclear, and the insulation layer complicates the thermal boundary conditions, limiting the direct applicability of existing ampacity calculation methods. Based on the Morgan model framework, this paper proposes an ampacity calculation method that accounts for the “plastic-then-elastic” deformation characteristics of compacted conductors. Material plastic flow and elastic deformation of the substrate are incorporated to refine the formulations for interlayer thermal contact conductance and thin-layer air gap thickness, while the equivalent distance of air voids is corrected using the fill factor. An iterative convergence procedure for the insulation outer surface temperature is established to accurately evaluate conductor Joule losses. Validated by wind tunnel tests on JKLGYJ 240/30 cables, the proposed method yields a radial temperature difference of 2.41 °C, closely matching the measured 2.6 °C, with an error of 7.4% compared to 13.5% for the conventional Morgan model. Parametric analysis reveals that equivalent radial thermal conductivity is independent of external environmental factors. Conductor stress has a negligible effect on the ampacity (variation < 0.1%). Under low wind speeds (0–5 m/s), the ampacity increases substantially with wind speed. Full article

Aerodynamic drag is a key factor influencing performance in high-speed winter sports, and even small reductions in drag may contribute to meaningful improvements in race time. This study investigated the effects of seam position and seam-folding direction on the aerodynamic characteristics of skiwear fabrics using wind tunnel experiments with two simplified models: a cylinder model and a wing-shaped model. In the cylinder model, the seam position directly facing the airflow was defined as 0° and shifted in 30° increments, whereas in the wing-shaped model, the seam was moved rearward from the foremost point in 5 cm increments. The inward-folded portion of the seam was arranged either toward the airflow or opposite to it. Wind tunnel tests were conducted at wind speeds ranging from 40 to 120 km/h, and drag coefficients were calculated from measured drag forces. The results show that aerodynamic drag varied with seam position in both models. In the cylinder model, the lowest drag coefficient was observed at 30° from the front, whereas in the wing-shaped model, the lowest drag was obtained at the foremost seam position (0 cm). At 100 km/h, shifting the seam position from 0 cm to 5 cm increased the drag coefficient by approximately 54.5% in seam type A and 50.0% in seam type B. These findings suggest that seam position may be a potentially relevant aerodynamic design variable in skiwear research, whereas seam-folding direction appeared to be of secondary importance under the present test conditions. However, the present conclusions are restricted to simplified experimental geometries and should not be directly generalized to specific body regions or full-garment systems. Full article

This paper presents the development of a novel morphing wing prototype with three camber-twist morphing flaps. Reflexed airfoil morphing is achieved by means of two chordwise degrees-of-freedom, thereby decoupling lift from the aerodynamic moment with respect to the aerodynamic centre. The prototype wing design is characterised by a novel morphing flap concept and driven by the boundary conditions pertinent to the wind tunnel testing facilities and the choice of research questions. The flaps’ spanwise ends are adapted to represent a seamless and a discontinuous transition between adjacent flaps. Linear electric motors induce the morphing shapes, equipped with load cells on their respective push rods, for actuator force measurement. Pressure taps are included to measure the pressure distribution along the wing section. Upon manufacturing, preliminary static test results validate the wing’s morphing functionality. The morphing trailing edge demonstrates a range of camber morphing and twist morphing shapes, as well as the ability to support asymmetric morphing between adjacent flaps. Full article

Glass curtain walls are widely used in the enclosure structure of airport terminals due to their advantages of lightweight and beautiful appearance, good lighting, and easy installation. However, coastal areas are constantly affected by typhoons, and under the influence of strong winds, complex pressure distributions are generated on the surface of curtain walls. Therefore, studying the wind pressure distribution characteristics of glass curtain walls is crucial for the structural safety and durability of coastal airport terminals. Based on this, accurately predicting wind pressure distribution not only helps to improve the design safety of airport terminals but also effectively prevents potential damage under strong wind conditions. To achieve effective prediction of wind pressure on glass curtain walls, this paper adopts a combination of wind tunnel tests and neural network prediction models. Real wind pressure coefficient data is obtained through wind tunnel tests, and a CNN–Transformer combination model is proposed to predict wind pressure coefficients. The results show that the prediction accuracy of the combined model is higher than that of the CNN and Transformer single models. MAE is optimized by 0.04~0.10 compared with the former and 0.16~0.34 compared with the latter; RMSE has been optimized by 0.02–0.10 and 0.30–0.34, respectively. This article can provide reference for the prediction research of wind pressure on the surface of glass curtain walls in airport terminals. Full article

The retrofitting of existing stadiums with retractable roof systems presents a complex interdisciplinary challenge, requiring the reconciliation of aged structural capacity with modern performance demands. This paper investigates the engineering design and analysis of a new retractable roof system for the Ningbo (Yinzhou) Tennis Center, a facility originally completed in 2007 and now requiring an upgrade to host higher-tier WTA 500 events. The retrofit is further complicated by increased seismic design requirements and the need to preserve the existing structure. To address these constraints, this study proposes a novel, structurally independent roof system comprising 12 radially deployable units supported by an external single-layer spatial grid and lambda-shaped columns. A multidisciplinary approach integrates structural engineering, mechanical systems, and architectural technology. Key innovations include (1) the selection and detailed modeling of a rack-and-pinion drive mechanism, with a floating engagement design to accommodate dynamic load transfer; (2) a two-stage analytical framework employing both sub-assembly and integrated assembly finite element models to capture the unique mechanical behavior and coupling effects between the new and existing structures; (3) the strategic implementation of circumferential hoop cables to counteract uplift forces and redirect the internal force distribution in the supporting bifurcated columns; and (4) the validation of structural integrity through comprehensive static, stability, and seismic gap analyses, informed by wind tunnel testing. The results demonstrate that the proposed system satisfies all strength, stiffness, and stability criteria under multiple operational states (open, closed, and transitional) and meets the enhanced seismic fortification standards. This research provides a validated theoretical foundation and practical implementation guidelines for this specific stadium retrofit, demonstrating a viable pathway for extending the service life of aging sports infrastructure, with insights that may inform similar urban renewal projects under comparable conditions. Full article

The limited self-starting capability of H-type Darrieus Vertical-Axis Wind Turbines (VAWT) remains one of the main obstacles to their deployment in low-power and urban applications, where wind conditions are typically weak and intermittent. Although several passive geometric modification strategies have been proposed to enhance initial torque generation, most available studies rely predominantly on numerical simulations, with limited systematic experimental validation under low tip-speed ratio (TSR) conditions. In this work, the influence of passive blade modifications on self-starting performance is assessed through a combined numerical–experimental approach. An integrated numerical–experimental framework was used to systematically compare passive blade configurations under equivalent low-wind conditions. Two modified configurations, a biomimetic profile incorporating passive trailing-edge devices and an asymmetric J-type geometry, were optimized using transient CFD simulations of the first rotation cycle and a Design of Experiments (DOE) framework. Additively manufactured full-rotor test blades were then manufactured via additive manufacturing and tested in a controlled wind tunnel at 3.0 m/s and 2.25 m/s. Start-up time, azimuthal robustness, tip-speed-ratio evolution, and static start-up torque (interpreted through its corresponding torque coefficient) were measured and compared against a baseline NACA0018 profile. The biomimetic configuration consistently produced higher start-up torque and shorter acceleration times, achieving self-starting in 66.7% of the evaluated azimuthal positions at 2.25 m/s, compared to 22.2% for the baseline profile. Within the investigated operating range, this configuration emerged as the most robust passive strategy. The agreement between CFD predictions and experimental measurements supports the use of first-cycle maximum torque as a representative indicator of self-starting performance. These findings highlight the comparative value of first-cycle maximum torque as a practical metric for passive self-starting design assessment in low-TSR Darrieus turbines. These findings provide direct experimental evidence to guide the rational design of Darrieus turbines intended for marginal wind conditions. Full article

Airfoil flow-field prediction is important for aerodynamic design, but wind-tunnel testing and computational fluid dynamics (CFD) remain costly and time-consuming. Deep learning enables fast inference, yet many existing models still rely on fixed grid representations, which may lead to insufficient learning in high-gradient regions and larger local errors. This study proposes Spatial Multilayer Perceptron (Spatial MLP) together with an Error-Gradient-Guided Data Sampling (EGDS) strategy for airfoil flow-field prediction. Spatial MLP adopts a coordinate-based point-wise prediction framework. A spatial decoder is introduced as an auxiliary branch to enhance global flow consistency during pretraining, while channel-wise multi-head attention is incorporated to improve cross-variable feature coupling. EGDS prioritizes physically informative points according to relative prediction error and gradient magnitude, while retaining random samples to preserve data diversity. Experiments on an independent test set show that Spatial MLP reduces the mean relative error (averaged over the velocity components u, v, and pressure p) by 15.2% relative to the MLP baseline. With EGDS, the overall mean relative error is further reduced by 34.5% relative to the MLP baseline. These results demonstrate that combining global consistency constraints with targeted sampling effectively improves both global prediction accuracy and local reconstruction quality in high-gradient flow regions. Full article

This work presents an experimental aerodynamic study of a Mars rover model, aimed at characterizing its flow behavior under Martian environmental conditions. Due to the extremely low Reynolds numbers associated with Mars’ thin atmosphere, the experiments were conducted using a scaled model of the rover manufactured via additive techniques. The study first focuses on understanding how the geometry of the rover influences the overall flow field, identifying key aerodynamic features such as separation zones, vortical structures, and flow reattachment regions driven by the complexity of the vehicle. A comprehensive investigation of the flow around the model was performed using both a hydrodynamic towing tank with dye injection for qualitative visualization, and particle image velocimetry (PIV) for quantitative flow field analysis in wind tunnel tests. After the general flow characterization, a more detailed local analysis was conducted using laser Doppler anemometry (LDA). This phase of the study targeted precise velocity measurements at specific locations corresponding to the MEDA (Mars Environmental Dynamics Analyzer) wind sensors onboard the rover. Quantitative results indicate that the central body induces a local flow acceleration of 20% to 40% relative to the free stream while severe turbulence was recorded in specific angular sectors, with velocity fluctuations reaching up to 120% for Sensor 1 and 90% for Sensor 2. Full article

Previous studies and current wind-load standards for low-aspect-ratio circular structures primarily consider external pressure and insufficiently address the combined effects of roof openings, internal–external-pressure interaction, and surface roughness. To overcome these limitations, this study investigates the net-pressure characteristics of such structures through wind-tunnel experiments conducted for two aspect ratios and four levels of surface roughness. The vertical variation in net pressure and its implications for wind-load estimation are systematically examined. For smooth surfaces, the net-pressure distribution exhibits pronounced height dependence due to the free-end effect. This dependence diminishes as surface roughness increases, indicating a significant modification of the flow structure around the cylinder. Neglecting this height-dependent behavior leads to substantial inaccuracies in drag-coefficient estimation. Comparisons with existing standards reveal that the drag coefficients specified in AS/NZS 1170.2 and AIJ-RLB overestimate values for smooth surfaces by up to 38.7% and 21.5%, respectively, whereas the AIJ-RLB provisions underestimate values for rough surfaces by approximately 4.7%. To improve predictive accuracy, a simplified model for the circumferential distribution of mean net-pressure coefficients is developed. The proposed model incorporates height-dependent aerodynamic parameters and demonstrates strong agreement with experimental data, with a maximum relative error below 8.6%. This model provides a practical reference for more reliable wind-load estimation in the structural design of low-aspect-ratio circular structures with roof openings. Full article

This work presents an integrated experimental and numerical determination of the aerodynamic (lift) characteristics of an ogive forebody equipped with all moving canards. Experimental testing was conducted in the subsonic custom-made wind tunnel of the Vlatacom Institute at a nominal free stream velocity of 32 m/s (and Mach number M = 0.09). Aerodynamic loads on the canards were measured using a custom one-component force balance, while free stream flow properties were obtained via a calibrated Pitot–Prandtl probe on the full-scale geometry model. On the numerical side, RANS simulations were performed in ANSYS Fluent using the k-ω SST turbulence model. Two geometric representations were considered: (a) a high-fidelity configuration explicitly resolving the physical gap between the canard and ogive, and (b) a simplified configuration with the gap removed. Boundary conditions, Reynolds number, and operating parameters were matched to the wind tunnel conditions to enable a strict one-to-one comparison. Particular emphasis was placed on examining the effect of geometric simplification on the predicted lift characteristics. The gap-resolved configuration reproduces the experimentally measured lift curve within approximately 10% across the investigated angle-of-attack range, satisfying conventional aerodynamic validation criteria. The results confirm both the robustness of the applied RANS approach for highly three-dimensional separated flows often found in engineering applications, as well as the reliability of the experimental measurement system. Full article

The present study proposes a full-scale experimental methodology for testing and quantifying the trajectory deviations induced in road vehicles. A full-scale articulated bus was employed in this work and tested under real operating conditions. In its foreseen exploitation use, the vehicle will, under certain conditions, be automatically guided (to cross bridges and tunnels and to approach and stop at bus stops). A series of tests was conducted on a bridge under different transverse wind conditions. It is important to note that the deviation measured by the laser system includes both the inherent deviations of the optical guidance system (OGS) and those induced by wind. It was observed that, despite trajectory variability, when measured at high spatial resolution (±1 mm) during the approach phase upstream of the test zone, the optical guidance system corrected deviations from the ideal trajectory within a short time interval and over a short distance. The system’s response shows reasonable agreement with the manufacturer’s results reported in the OGS study. The results also show some degree of dispersion, given multiple sources of uncertainty inherent to full-scale testing under real operating conditions. The findings show that the OGS’s dynamic response is adequate to reduce disturbances to the vehicle’s trajectory caused by crosswind. Full article

The inhibitory effect of vegetation on soil wind erosion along grassland highways in semi-arid regions has not been fully elucidated. In this study, the dry vegetation near S105 provincial highway in the Sangendalai area of Xilingol League, Inner Mongolia was selected for a wind tunnel test, and the vegetation coverage and porosity during the test were determined by using image processing methods. On this basis, a porous medium model of dry vegetation was established, and the two-phase flow of wind and sand was numerically simulated. The results show that: (1) The numerical simulation results are in good agreement with the wind tunnel observations, confirming the feasibility of using CFD to simulate wind erosion affected by vegetation along grassland highways in semi-arid areas. (2) The aerodynamic roughness of the grassland surface increases nonlinearly with the increase of vegetation cover, and the increase of aerodynamic roughness is more obvious when the vegetation cover is more than 16% in the scope of this study. (3) Vegetation changed the typical jump-dominated wind–sand flow structure on the bare ground surface, showing a significant interception and attenuation effect of vegetation, which was manifested by the reduction of sand accumulation at the wind outlet and the increase of deposition within the vegetated area, thus effectively inhibiting the wind erosion process. The results of the study provide methodological references and a theoretical basis for the study of wind erosion along grassland highways in semi-arid regions and help to promote the sustainable development and ecological balance of grassland ecosystems in semi-arid regions. Full article

This paper presents an experimental investigation of the level flight speed and endurance characteristics of a micro-class unmanned aerial vehicle as a function of operating weight. Wind tunnel experiments were conducted to determine the aerodynamic performance and power requirements of the UAV over a range of operating weight configurations. The tested vehicle, a fixed-wing micro UAV, was examined under steady, level flight conditions, with particular emphasis on identifying variations in the minimum power required to sustain level flight. Measured aerodynamic forces and moments were used to derive drag polars and the corresponding power curves for each mass configuration. Based on these results, endurance estimates were obtained by coupling the experimentally derived power requirements with the characteristics of the onboard electric propulsion system. The study demonstrates a clear shift in flight speeds with increasing operating weight, as well as a reduction in achievable endurance, highlighting the sensitivity of micro-class UAV performance to mass variations, and therefore energy consumption. Full article

In modern society, distributed photovoltaics are widely used, and overhead photovoltaic roofs are favored for their many advantages; however, they are vulnerable to failure during high-wind events. Parapets are common auxiliary structures on building rooftops. Wind tunnel testing was employed to investigate the effects of parapet configurations on wind pressures acting on overhead photovoltaic (PV) roofs. Results show that wind suction dominates, with maximum negative pressure consistently at the windward corner leading edge. A solid parapet significantly increases the maximum mean pressure coefficient, whereas perforated parapets have little effect. In most cases, parapets reduce fluctuating pressure coefficients. Extreme pressure distribution exhibits significant regional characteristics, with the most unfavorable area at the roof corner. The solid parapet increases unfavorable extreme values at the corner. Horizontal and rectangular grid parapets reduce extreme pressure coefficients at the high-eave corner with minimal impact on the low-eave corner, while the vertical parapet increases values at the low-eave corner. Under the conditions of this experiment, among the four parapet types, the horizontal and rectangular grid parapets have little effect on the mean wind pressure and significantly reduce the peak wind pressure, thereby helping to ensure the wind resistance safety of the photovoltaic roof. Full article