Search Results (557)

This work presents an extensive experimental and numerical analysis, aimed at investigating the impact of shelf-like fences applied on the suction side of a turbine nozzle guide vane. The cascade is constituted of vanes characterized by long chord and low aspect ratio, which are typical features of some LPT first stages directly downstream of an HPT, hence presenting high channel diffusion, especially near the tip. In particular, the present study complements existing literature by highlighting how blade fences positioned on the suction side can reduce the penetration of the large passage vortex. This is particularly effective in applications where flow turning is limited, the blades are lightly loaded at the front, and the horseshoe vortex is weak. The benefits of the present fence design in terms of losses and flow uniformity at the cascade exit plane have been demonstrated by means of a detailed experimental campaign carried out on a large-scale linear cascade in the low-speed wind tunnel installed in the Aerodynamics and Turbomachinery Laboratory of the University of Genova. Measurements mainly focused on the characterization of the flow field upstream and downstream of straight and fenced vane cascades using a five-hole pressure probe, to evaluate the impact of the device in reducing secondary flows. Furthermore, experiments were also adopted to validate both low-fidelity (RANS) and high-fidelity (LES) simulations and revealed the capability of both simulation approaches to accurately predict losses and flow deviation. Moreover, the accuracy in high-fidelity simulations has enabled an in-depth investigation of how fences act mitigating the effects of the passage vortex along the blade channel. By comparing the flow fields of the configurations with and without fences, it is possible to highlight the mitigation of secondary flows within the channel. Full article

In the research and development system of bat-like flapping-wing flying robots, lift modeling and numerical analysis are the key theoretical basis, which will directly affect the construction of the body structure and flight control system. However, due to the complex three-dimensional flapping motion mechanism of bats and the flexible deformation characteristics of their wing membranes, the existing lift theory lacks a mature calculation method suitable for bionic flapping-wing flying robots. In this paper, the wing membrane deformation mechanism of a bat-like flapping-wing flying robot is studied, and the coupling effect of wing membrane motion and deformation on flight parameters is analyzed. A set of calculation methods for flexible morphing wing membrane lift is improved by using a quasi-steady model and the blade element method. By comparing and analyzing the theoretical calculation and experimental results under various working conditions, the error is less than 4%, which proves the effectiveness of this method. Full article

Farmland shelterbelts are vital ecological infrastructure for sustaining agriculture in arid regions, where high winds, soil erosion, and water scarcity severely constrain productivity. While their protective functions—reducing wind speed, controlling erosion, moderating microclimates, and enhancing yields—are well documented, previous studies have largely examined individual structural elements in isolation, leaving their interactive effects and trade-offs poorly understood. This review synthesizes current research on the structural optimization of shelterbelts, emphasizing the critical relationship between their physical and biological attributes and their protective functions. Key structural parameters—such as optical porosity, height, width, orientation, and species composition—are examined for their individual and interactive impacts on shelterbelt performance. Empirical and modeling studies indicate that moderate porosity maximizes wind reduction efficiency and extends the leeward protection zone, while multi-row, multi-species configurations effectively suppress soil erosion and improve microclimate conditions. Sheltered areas experience reduced evapotranspiration, increased humidity, and moderated temperatures, collectively enhancing crop water use efficiency and yielding significant improvements in crop production. Advanced methodologies, including field monitoring, wind tunnel testing, computational fluid dynamics, and remote sensing, are employed to quantify benefits and refine designs. A multi-objective optimization framework is essential to balance competing goals: maximizing wind reduction, minimizing water consumption, enhancing biodiversity, and ensuring economic viability. Future challenges involve adapting designs to climate change, integrating water-efficient and native species, leveraging artificial intelligence for predictive modeling, and addressing socio-economic barriers to implementation. Building on this evidence, we propose a multi-objective optimization framework to balance competing goals: maximizing wind protection, minimizing water use, enhancing biodiversity, and ensuring economic viability. We identify key research gaps including unresolved porosity thresholds, the climate resilience of alternative species compositions, and the limited application of optimization algorithms and outline future priorities such as region-specific design guidelines, AI-driven predictive models, and policy incentives. This review offers a novel, trade-off–aware synthesis to guide next-generation shelterbelt design in arid agriculture. Full article

Accurate wind field modeling over hilly terrain is critical for wind energy, infrastructure safety, and environmental assessment, yet its inherent complexity poses significant simulation challenges. This paper systematically reviews this field’s major advances by analyzing 610 key publications from 2015 to 2024, selected from core databases (e.g., Web of Science and Scopus) through targeted keyword searches (e.g., ‘wind flow’, ‘complex terrain’, ‘CFD’, ‘hilly’) and subsequent rigorous relevance screening. We critique four primary modeling paradigms—field measurements, wind tunnel experiments, Computational Fluid Dynamics (CFD), and data-driven methods—across three key application areas, filling a gap left by previous single-focus reviews. The analysis confirms CFD’s dominance (75% of studies), with a clear shift from idealized 2D to real 3D terrain. Key findings indicate that high-fidelity coupled models (e.g., LES), validated against benchmark field experiments such as Perdigão, can reduce mean wind speed prediction bias to below 0.1 m/s; and optimized engineering designs for mountainous infrastructure can mitigate local wind speed amplification effects by 15–20%. Data-driven surrogate models, represented by FuXi-CFD, show revolutionary potential, reducing the inference time for high-resolution wind fields from hours to seconds, though they currently lack standardized validation. Finally, this review summarizes persistent challenges and outlines future directions, advocating for physics-informed neural networks, high-fidelity multi-scale models, and the establishment of open-access benchmark datasets. Full article

This study presents the design, numerical analysis, and experimental validation of an innovative wind turbine blade incorporating an internal flow channel and tangential slots to harness the Coanda effect for enhanced aerodynamic performance. The primary objective is to improve thrust generation and lift while reducing drag, thereby increasing the efficiency of wind turbines and potential aerial propulsion systems. A three-dimensional blade model was developed in COMPAS-3D and fabricated using PET-G filament through 3D printing, enabling precise realization of the internal geometry. Computational fluid dynamics (CFD) simulations, conducted in ANSYS Fluent using a refined mesh and the k—ω SST turbulence model, revealed that the proposed blade design significantly improves pressure distribution and airflow attachment along the blade surface. Compared to a conventional blade under identical wind conditions (12 m/s), the innovative blade achieved a 12% increase in power coefficient, lift force of 33 N and drag force of 60 N, validating the efficacy of the Coanda-based flow control. Wind tunnel experiments confirmed the numerical predictions, with close agreement in thrust and lift measurements. The blade demonstrated consistent performance across varying wind velocities, highlighting its applicability in renewable energy systems and passive flow control for aerial platforms. The findings establish a practical, scalable approach to aerodynamic optimization using structural enhancements, contributing to the development of next-generation wind energy technologies and efficient propulsion systems. Full article

This study presents a computational fluid dynamics (CFD) modeling framework to simulate two-phase (liquid and gas) chemical agent dispersion in urban canyons. The model was validated against wind tunnel experiments, meeting statistical criteria. To assess geometric impacts on flow and dispersion, the model was applied to four idealized canyon types—Cube (CB), Short (SH), Medium (MD), and Long (LN). Results revealed that increasing building length reduced the horizontal extent but enhanced the vertical extent of wake zones, weakened roof-level wind speeds, and shifted the reattachment point farther downstream. For liquid-phase sulfur mustard (HD), CB showed active canyon exchange and rapid penetration to pedestrian level. SH and MD exhibited more gradual infiltration with weaker variability due to fewer streamwise streets. LN had no streamwise street; transport was primarily driven by canyon vortices and showed slower penetration. Gaseous HD exhibited similar patterns to liquid HD but attained higher in-canyon concentrations due to differences in evaporation and dry deposition effects, indicating prolonged persistence. Overall, canyon geometry strongly influenced pollutant retention and variability. These findings suggest that the model can support chemical hazard assessment and early response planning that considers building geometry. Full article

Wind tunnel experiment serves as a primary method for characterizing grid fin aerodynamics, yet a fundamental conflict arises between facility size constraints and the structural vulnerability of excessively thinned grid fins from aggressive scaling, which might prevent viable experiments from being conducted. This study addresses this limitation by proposing two aerodynamic approximation methods, namely the unconstrained cell chord ratio method and the unconstrained external frame dimensions method, which generate aerodynamically equivalent configurations by strategically reducing the number of cells within the external frame to increase structural thickness. Through combined computational fluid dynamics (CFD) simulations and wind tunnel experiments analyzing full-scale isolated grid fins, full-scale launch vehicles equipped with grid fins, and their 1:25 scaled counterparts, both methods demonstrably outperform the published supersonic linearization approximation method. Critically, once the cell number is not excessively reduced, the unconstrained frame method maintains identical variation trends in aerodynamic forces, moments, and rudder control effectiveness compared to the baseline configuration, with maximum deviations constrained within 3% across tested conditions. This precision validates the exceptional suitability of the method for aerodynamic approximation of scale-down grid-fin-equipped launch vehicles in wind tunnel experiments, resolving the critical trade-off between test feasibility and structural strength. Full article

In our previous study, the transition behavior of a flared cone–swept fin configuration was investigated under an angle of attack (AoA) of 0°. To further explore the role of AoA in complex three-dimensional geometries with strong fin–body interactions, wind tunnel experiments were conducted at Ma = 9.3, Re = 1.36 × 10⁷/m, with AoA ranging from −6° to 6°. Global surface temperature distributions were obtained using temperature-sensitive paint (TSP), while localized heat flux and pressure fluctuations were captured using thin-film thermocouples and high-frequency pressure sensors. The results show that varying AoA shifts the location of high heat flux between the upper and lower surfaces of the flared cone and induces a switch from streamwise to separation vortices. The windward side exhibits stronger disturbance responses than the leeward side. The junction region between the flared cone and the near-horizontal surface is highly sensitive to AoA variations, consistently exhibiting pronounced second-mode instabilities. These findings provide experimental support for understanding transition mechanisms under the combined effects of shock/boundary layer interaction (SBLI), crossflow, and adverse pressure gradients, with implications for transition prediction and thermal protection system design. Full article

Straight-walled diffusers can boost the power density of horizontal-axis hydrokinetic turbines (HKTs), but are prone to boundary layer separation when the divergence angle is too large. We perform a systematic factorial study of three diffuser configurations, slotless, mid-length single-slot, and outlet-slot with dual divergence angles, using a two-dimensional, transient SST k–$\omega$ Reynolds-averaged Navier–Stokes model validated against wind tunnel data (maximum error 6.4%). Eight geometries per configuration are generated through a $2^3$ Design of Experiments with variation in the divergence angle, flange or slot position, and inlet section. The optimal outlet-slot design re-energises the boundary layer, shortens the recirculation zone by more than 50%, and raises the mean axial velocity along the diffuser centreline by 12.6% compared with an equally compact slotless diffuser, and by 42.6% relative to an open flow without a diffuser. Parametric analysis shows that the slot position in the radial (Y) direction and the first divergence angle have the strongest influence on velocity augmentation. In contrast, the flange angle and axial slot location (X) are second-order effects. The results provide fabrication-friendly guidelines, restricted to straight walls and a single slot, that are capable of improving HKT performance in shallow or remote waterways where complex curved diffusers are impractical. The study also identifies key geometric and turbulence model sensitivities that should be addressed in future three-dimensional and multi-slot investigations. Full article

Co-flow jet (CFJ) is an active flow control technique that significantly enhances aerodynamic performance metrics such as the maximum lift and maximum lift-to-drag ratio of airfoils or wings. Currently, investigations into lift enhancement and drag reduction on three-dimensional CFJ swept wings are limited. To address this issue, we used a low-speed, high-lift NPU-LS 0515 airfoil as a baseline and designed a wind tunnel experimental model of a CFJ swept wing, with the CFJ driven by internally mounted ducted fans and guided by injection ducts. We investigated the effects of jet direction, jet momentum coefficient, and injection slot size on lift enhancement and drag reduction performance of the CFJ swept wing through wind tunnel experiments. Experimental results showed that chord-wise vortices generated by the interaction of the deflected jet flow with the main flow through shear stress effectively enhanced mixing effect and energy transfer, improving the lift coefficient of the CFJ swept wing. Compared to the baseline configuration, the CFJ swept wing achieved over a 20% increase in maximum lift coefficient and more than a 50% reduction in drag coefficient at high angles of attack. Consequently, the lift-to-drag ratio of the swept wing improved substantially. Full article

This paper highlights recent activities associated with the design of an uninstalled open fan propulsor for next-generation civil aircraft in the high-subsonic flight regime. The concept comprises a transonic propeller–rotor and a subsequent guide vane, which are both subject to pitch-variability in order to account for the strong variations in flight conditions over the entire mission profile. The engine-scale design aimed for high technological maturity and to comply with a high number of industrially relevant requirements to ensure a competitive design, meeting performance requirements in terms of high efficiency levels at cruise and maximum climb conditions, operability in terms of stability margins, good acoustic characteristics, and structural integrity. During the design iterations, rapid 3D-RANS-based optimisations were only used as a conceptual design tool to derive sensitivities, which were used to support and justify major design choices in addition to established relations from propeller theory and common design practice. These design-driven optimisation efforts were complemented with more sophisticated CFD analysis focusing on rotor tip vortex trajectories and resulting in unsteady blade row interaction to optimise the guide vane clipping, as well as investigations of the entire propulsor under angle-of-attack conditions. The resulting open fan design will be the very basis for wind tunnel experiments of a downscaled version at low and high speed. Full article

The ablation process of a silica fiber-reinforced polymer (SiFRP) composite under aerodynamic heating and a shear environment was investigated by experiments and numerical study. The flat plate samples were tested in an arc jet wind tunnel under heat flux and pressure ranging from 107 W/cm² at 2.3 kPa to 1100 W/cm² at 84 kPa. The heating surface experiences shear as high as 1900 Pa. The in-depth thermal response and ablating surface temperature of the specimens are measured during ablation. According to the ablation experimental results, a multi-layer ablation model was established that accounts for the effects of carbon deposition, investigating the thermophysical properties of the ablation deposition layer. The accuracy of the proposed ablation model was evaluated by comparing the calculated and experimental surface ablation recession and internal temperature of a silica–phenolic composite under steady-state ablation. Carbon–silica reaction heat is the important endothermic mechanism for silica-reinforced composites. The research provides valuable reference for understanding the ablative thermal protection mechanism of silicon–phenolic composites in a high shear environment. Full article

Sand disasters significantly restrict ecological restoration and the development of sustainable transport infrastructure in desert areas, and the impact of varying subgrade width and roughness caused by different types and uses of routes on the wind-sand environment is still unclear. To address this, four typical subgrade widths were studied, and wind tunnel experiments were carried out using models. Near the ground surface (at heights < 8.3 cm), a 3.5 cm wide subgrade had a greater effect on the windward wind speed compared with three other widths. The distance required for wind speed recovery on the leeward of the 3.5 cm wide subgrade was greater than that for the three other widths. The 3.5 cm wide subgrade had a larger effect range and extent on the leeward wind flow field compared with the three other widths. The distance needed for the leeward wind flow field to recover at the 3.5 cm wide subgrade was also greater than that for the three other widths. The sand transport rates for the 14, 26, and 41 cm wide subgrades were similar and showed a consistent trend. However, the sand transport rate for the 3.5 cm wide subgrade was more variable and was lower than that for the three other widths at near-ground surface heights but higher at intermediate heights. Width has a minor effect on the wind-sand environment around the subgrades compared to roughness. The research findings provide insights into the relationship between the subgrade width, roughness, and wind–sand environment, offering guidance for mitigating sand disasters along transportation routes. It provides theoretical support for optimizing transportation infrastructure design, promoting green and low-carbon construction, and promoting ecological restoration around the routes. Full article

The fall armyworm, Spodoptera frugiperda, is a long-distance migratory pest, which invaded the African continent in 2016, causing enormous losses to agricultural crops, especially maize. Synthetic insecticides are primarily used for managing S. frugiperda, but they leave residues on human food and animal feed and also cause environmental hazards. We evaluated the crude ethanolic extract of Piper guineense fruits for contact toxicity on S. frugiperda larvae and determined the lethal concentration (LC₅₀) of the extract. Additionally, we conducted an electrophysiological (EAG) experiment to determine the responses of adult S. frugiperda males and females to P. guineense and determined whether the extract influenced mating, oviposition, and repellence to the adult female. We found that P. guineense extract caused significantly higher mortality to S. frugiperda larvae than an ethanol control. Electrophysiologically, we observed significantly higher responses to the extract than the control, with some variations in response between the sexes. A wind tunnel experiment revealed that females moved more towards the control than towards the extract. Taken together, our results confirm that P. guineense extract is effective against S. frugiperda larvae and adults. Future research should explore the responses of S. frugiperda to P. guineense extract on a field scale. Full article

The integration of three-dimensional inward-turning inlets with airframes has broad application prospects. This paper develops an integrated design method for the inlet forebody with a controllable incident shock wave shape, aiming at the three-dimensional inward-turning inlet with a circular entrance, and it is applied to the forebody design of a given inward-turning inlet to obtain a three-dimensional inward-turning inlet/forebody matching scheme. Numerical simulation and wind tunnel experiment were carried out to investigate the aerodynamic performance of the inlet. The results show that the inlet/forebody matching scheme successfully realizes both geometric and aerodynamic matching between the inlet and forebody, resulting in a shock-on-lip condition at the design point, with only a 2% reduction in mass flow rate. This indicates that the forebody design and matching method are highly effective. It should be noted that after the forebody matching is achieved, the overall compression effect of the inlet on the airflow is weakened, and both the Mach number and total pressure at the inlet outlet increase slightly. Full article