Chilling injury (CI) affects up to 33% of globally traded postharvest commodities, yet the influence of precooling conditions on CI susceptibility remains largely unexplored. This is likely due to the inherent complexity and variability of commercial operations. This study introduces a novel methodology to systematically evaluate precooling-CI interactions under controlled laboratory conditions. The approach is grounded in commercial precooling characteristics and comprehensive cold chain CI evaluation protocols. A laboratory forced-air cooling system was developed, consisting of wind tunnels installed in existing cold rooms to replicate commercial precooling airflow speeds and cooling rates. The wind tunnels operate over a 0.0-0.9 m s-1 range, with an uncertainty of <3.6% at a 99% confidence level. The system successfully reproduced commercial precooling conditions and induced statistically significant, differentiable CI responses in citrus trials. The methodology provides researchers with a reproducible platform for investigating precooling optimisation strategies and CI mitigation for both citrus and other fruit types, with potential applications in postharvest technology development and supply chain optimisation. Key methodological components include:•Characterisation of commercial precooling conditions to establish realistic design parameters•Development and application of a laboratory-scale wind tunnel precooling simulator•Chilling injury evaluation protocol for precooling protocol assessment.

AR Tunnel: An augmented-reality digital twin for immersive learning of wind tunnel laboratories

The global rise in energy demand, driven by modern lifestyles, necessitates more efficient wind energy harvesting. This research aims to determine the optimal blade angle for enhancing aerodynamic performance in Horizontal Axis Wind Turbines (HAWTs) under specific wind conditions. Computational and experimental analyses were conducted to evaluate lift and drag forces across different blade angles, focusing on maximizing moment and power output. The results identify 82° as the optimal blade angle for peak performance, with maximum moment observed at this angle for wind speeds of 3 m/s, 12.5 m/s, and 25 m/s. CFD simulations using ANSYS Fluent 17.0 with NACA aerofoils were validated through experiments, showing strong agreement between theoretical and experimental results. The study establishes a rated tip speed of 105 m/s for a 5 MW HAWT. By integrating experimental and computational approaches, this research provides valuable insights into the aerodynamic behavior of HAWTs, aiding in the development of efficient airfoils and blades to enhance energy generation. The findings highlight CFD's role as a cost-effective and time-efficient tool for assessing blade and wind characteristics, contributing to the optimization of wind energy systems and the advancement of sustainable energy solutions. • Integration of computational, theoretical, and experimental methods to optimize HAWT performance • Identification of optimal blade angles to enhance efficiency at low wind speeds • Analysis of wind turbine performance using ANSYS Fluent and wind tunnel experiments • Insights into the impact of wind speed variations on electricity production • Comprehensive evaluation of aerodynamic forces influencing HAWT performance

This study introduces a non-intrusive Particle-Tracking Velocimetry (PTV) technique to simultaneously measure aeolian transport velocity, concentration, and mass flux profiles, overcoming the flow disruption and uncertainty issues of traditional sand traps. By analyzing particle trajectories frame-by-frame, this image-based method enables high-resolution spatiotemporal analysis without disturbing the flow. The derived vertical mass flux, calculated as the product of velocity and concentration, revealed that particle velocity increases logarithmically with height while particle concentration decreases exponentially. Notably, particle concentration was identified as the dominant factor driving surface mass flux. The vertically integrated mass fluxes, or total aeolian mass flux, showed strong agreement with a theoretical model supporting a quadratic dependence of mass flux on shear velocity rather than traditional cubic scaling models. The proposed PTV technique demonstrates significant potential as a reliable measurement tool for validating theoretical predictions and providing high-quality observation data in the field of coastal engineering and environmental management. • A non-intrusive PTV method quantifies aeolian velocity, concentration, and mass flux. • Vertical mass flux profiles show concentration dominates transport near the surface. • Total aeolian mass flux follows a quadratic scaling with shear velocity. • Measured fluxes agree closely with physically based transport models.

Performance evaluation of a fan-array wind tunnel for advanced aerodynamic studies

Energy harvesting properties of flexible piezoelectrets under wind-induced vibration

The energetic performance of railway vehicles is becoming increasingly important, including for low-speed trains operating on regional and inter-city routes. Aerodynamic drag significantly affects train power consumption, making its accurate estimation essential for the design of energy-efficient rolling stock. Numerical simulations are widely used to estimate aerodynamic resistance; however, simplified fluid-dynamics approaches may lead to inaccurate predictions, particularly for the complex geometries typical of regional trains. This paper compares two numerical methods — Reynolds-Averaged Navier–Stokes (RANS), widely adopted in industry, and the state-of-the-art Improved Delayed Detached-Eddy Simulation (IDDES) — against wind tunnel experiments. Two train geometries are analysed: a conventional regional-train shape and a modified, more streamlined configuration. The analysis focuses on the global aerodynamic drag predicted by the numerical approaches and compares it with experimental measurements. Both methods show satisfactory agreement with the experiments, although noticeable differences emerge. Significant discrepancies are observed in highly turbulent regions, such as the tail, roof, and bogie areas, with IDDES consistently predicting higher drag levels than the RANS model. This work provides new insights into the aerodynamics of regional trains, a vehicle category that has received limited attention so far, and offers results of practical relevance to the railway industry. • Comparison between RANS and IDDES turbulence models for regional-train aerodynamics. • Effects of turbulence models on bluff and streamlined train geometries. • Evaluation of drag contributions along the train using sectional and cumulative aerodynamic coefficients. • Assessment of the influence of roof-mounted equipment and bogie geometry on drag prediction.

Comprehensive evaluation of the SST k-ω model for building environment applications: comparison with k-ε models, LES, and wind tunnel experiments

Skin friction measurement of the turbulent boundary layer at very high Reynolds numbers on a wind tunnel wall using a floating element device

Bumblebees rely on diverse sensory information to locate flowers while foraging. The majority of research exploring the relationship between visual and olfactory floral cues is performed at local spatial scales and applicable to understanding floral selection. Floral-cue use during search remains underexplored. This study investigates how the bumblebee Bombus impatiens uses visual versus olfactory information from flowers across behavioral states and spatial scales. At local spatial scales, non-flying animals in an associative learning paradigm will generalize to either unimodal attribute of a learned color+odor cue with equal likelihood. However, bumblebees flying in a wind tunnel shift cue-use strategy depending on the spatiotemporal scale of cue encounter. When both color and odor cues mimic local/ within patch spatial scale, bumblebees weigh color information of a learned floral-cue more heavily. When cues mimic an intermediate/ between patch spatial scale, bumblebees weigh color and odor information equally, and show the highest response to fully intact multimodal cues. Thus the spatiotemporal scale of sensory information influences how bumblebees utilize multimodal floral cues.

Wind erosion in arid and semi-arid regions poses a significant global environmental challenge, threatening infrastructure and human health. Conventional enzymatic-induced carbonate precipitation (EICP) for soil stabilization, while effective, relies on the natural urease enzyme extracted from plants or microorganisms, thereby being limited by extraction methods, purification levels, and the availability of biological sources, as well as the natural enzyme's environmental sensitivity. This study introduces a novel approach utilizing synthetic urease-mimetic catalysts to induce calcite precipitation for dust suppression. Two Schiff base complexes, derived from glycine and salicylaldehyde with central metal ions of copper(II) and zinc(II), were synthesized and evaluated as catalysts for urea hydrolysis. The zinc-based complex was selected as the superior catalyst based on higher calcite precipitation yield and lower cost. Through response surface methodology (RSM) and wind tunnel testing on erodible siliceous sand, the optimal application parameters were determined to be a solution containing 8g/L urea, 13g/L CaCl₂, and 1g/L Zn-complex applied at a rate of 1.65L/m². This treatment effectively reduced wind erosion to negligible levels (mass loss per original mass of the sample ~ 1%). Supplementary tests, including successive wet-dry cycles, surface strength measurement, and SEM analysis, confirmed the formation of a durable calcite crust that bonds soil particles, increasing surface strength to over 150kPa. The stabilized soil exhibited excellent resistance to simulated environmental stressors, including heat (50°C) and long-term aging (one year), with only a minimal increase in erosion (mass loss percent of 1.5%). This research demonstrates that Schiff base complexes, particularly the zinc variant, are highly effective and durable catalysts for soil stabilization via chemical carbonate precipitation, offering a promising alternative to biological enzyme-based methods.

Abstract This paper presents an experimental investigation of the properties of long electrical arcs immersed in a crossflow. The insights gained from these experiments can be applied in numerous fields: one of which is lightning protection of aircraft. Upon initial attachment to the airplane, the lightning arc column can sweep along the plane's surface due to the relative motion between the two in a process known as the swept-stroke. The first set of experiments corresponds to meter-scale low-current D.C. arcs (3 A) attaching to an aeronautic airfoil in low speed flow (1-4 m/s), extending prior work that considered an anodic airfoil to the negative polarity case. The dynamic and electrical properties of the arc channel, as well as the dynamic motion of the cathodic arc root, are investigated through high-speed imaging, particle image velocimetry (PIV), and electrical measurements. The influences of wind speed, airfoil angle of attack (AoA), and counter-electrode configuration are explored. The second set of results applies the same data processing to high-speed videos from a previous experimental campaign conducted at ONERA on meter-long high-current D.C. arcs (200-600 A) subject to high-speed flow (40-60 m/s). Unlike the anodic arc root, the cathodic arc root is observed to either stall or sweep along the airfoil surface. In general, the root trails the leading edge of the arc column, which is advected by the flow, with the degree of lag depending on the experimental conditions. These findings enable analysis of how flow separation, boundary layer dynamics, arc regimes, and cathode emission processes influence the physical behavior of the arc column and root over two orders of magnitude in current and one order of magnitude in wind speed, providing insight into the coupled phenomena governing the swept-stroke.

Natural antimicrobial composite membranes for effective filtration and inactivation of airborne bacteria and viruses.

This study investigates the aerodynamic characteristics of a swallow-inspired wing based on a NACA 2415 airfoil at Reynolds numbers of 7.5 × 104and 1.25 × 105using experimental force measurements and flow-visualization techniques. The bioinspired wing model was designed according to the top-view geometry of a swallow wing and tested in a low-speed open-suction wind tunnel together with a rectangular wing of identical planform area and airfoil profile to provide a baseline comparison. Aerodynamic measurements were conducted over an angle-of-attack range between -6° and 24° to determine lift, drag and moment coefficients as well as aerodynamic efficiency. In addition to force measurements, smoke-wire and TiO2based flow visualization techniques were used to examine the flow topology around the test models. The results show that the swallow-inspired wing exhibits improved aerodynamic performance compared with the rectangular configuration under both Reynolds number conditions. AtRe= 1.25 × 105, the bioinspired wing achieved a maximum lift coefficient of 0.694 at an angle of attack of 9°, while the minimum drag coefficient was approximately 7.48 × 10-3. The aerodynamic efficiency reached a maximumL/Dratio of 42.9 at an angle of attack of 2°. Similar aerodynamic trends were observed atRe= 7.5 × 104, although slightly reduced lift and aerodynamic efficiency were recorded due to stronger viscous effects at lower Reynolds numbers. The pitching moment coefficient varied approximately linearly with angle of attack, with a slope of -7.8 × 10-3per degree and a zero-lift moment value of -7.47 × 10-3, indicating stable longitudinal aerodynamic behavior. Flow visualization results revealed a gradual transition from attached laminar flow to separated turbulent flow, suggesting smoother stall development and improved flow stability for the bioinspired configuration. These findings highlight the aerodynamic advantages of swallow-inspired wing geometries and their potential to enhance aerodynamic efficiency in low Reynolds number flight.

SynopsisBird wings contain several feather groups, some of which contribute to their aerodynamic performance during flight. One of these groups is the emarginated primary feathers, which exhibit slots, bending, and twisting in flight. Slotted wingtips vary in morphology across the avian clade, raising questions about the relationship between their form and function, particularly with regard to their aerodynamic role. This study expands the current understanding of the functional morphology of slotted wingtips by systematically studying slots, bending, and twist using various engineered wingtip configurations: one that captures the slotting only, another that has both slotting and bending, and a third that combines slots, bending, and twist. Force, moment, and PIV data acquired during wind tunnel testing reveal that the bioinspired wingtips have both global and local aerodynamic effects. The wingtips’ global aerodynamic effect is to delay spanwise stall propagation, thereby altering the lift distribution over the wing. Local aerodynamic effects include the reduction of aerodynamic load over the wingtips as well as changes to the separated shear layer location and the breakdown of tip vorticity. The results show that while global aerodynamic effects are universal across all configurations, local effects are sensitive to wingtip design. Nonetheless, both the global and local effects enable structural resilience and effective roll and yaw control authority. These results demonstrate that the emarginated primary feathers may have multiple aerodynamic functions, offering new insights into their role in bird flight and showcasing their potential as flow- and flight-control devices for engineered aerial vehicles.

ABSTRACT Circular saw blades can radiate high levels of sound during idle running and cutting, primarily due to aerodynamically driven vibrations when vortex shedding frequencies coincide with structural resonances. In this study,d the influence of the spacing between two consecutive teeth on vortex-shedding phasing, unsteady lift forces, structural vibration, and tonal noise radiation were investigated. A two-dimensional scale adaptive simulation (SAS) model, representing two consecutive teeth as tandem rectangular bodies, is combined with wind tunnel measurements of aerodynamic force proxies, vibration, and far-field sound pressure level over an inlet velocity of 12 ms−1. The results reveal a critical pitch ratio (p/D ≈ 2.0, where p is the streamwise spacing between the leading edges of consecutive teeth and D is the characteristic tooth thickness) in which the shedding of the adjacent teeth is in phase, producing constructive interference, maximum unsteady lift, increased vibration amplitude, and elevated tonal noise levels. For p/D ⪆ 2.5, shedding shifts towards antiphase, reducing aerodynamic excitation, and broadening the acoustic spectrum. These findings provide a physical explanation for common idle tonal peaks and support design strategies that avoid uniform spacings near the critical ratio. The introduction of an irregular pitch disrupts phase coherence, mitigating tonal noise without compromising cutting performance.

In modern agriculture, both the "3R" (Resistance/Residue/Resurgence) problems caused by chemical insecticides and the issue that commercial sex pheromone attractants only lure male moths have driven researchers to urgently seek safer and more environmentally friendly alternatives. In this study, dynamic headspace adsorption method combined with GC-MS was employed to collect and identify volatile organic compounds emitted by mulberry leaves from different cultivars selected by female Glyphodes pyloalis (Lepidoptera: Pyralidae) (Walker, 1859) for oviposition. Subsequently, qualitative screening of active components with oviposition-attracting effects on female G. pyloalis was conducted using an EAG apparatus, a three-arm olfactometer, a wind tunnel device, and field trapping experiments. The results indicate that female G. pyloalis exhibit a strong preference for oviposition on mulberry varieties JS, XJ5, SH1, and Y1. Among the identified leaf volatiles, four compounds inciuding Hexacosane, Butyl acrylate, (E)-3-Hexen-1-ol, and 4-Hexen-1-ol, 1- acetate, elicited significant EAG responses and behavioral attraction in female moths. Specifically, compared with the CK, Butyl acrylate at a concentration of 10.0 μg/μL and (E)-3-Hexen-1-ol at 100.0 μg/μL produced the highest responses, with EAG amplitudes of 689.90 × 10-3 mV and 620.22 × 10-3 mV, respectively, the selection rates of female moths to them were 78.95% and 76.19%. Further screening and verification experiments confirmed that the optimal ratio of the novel "female moth-specific attractant" was Butyl acrylate: (E)-3-Hexen-1-ol = 19.627%: 15.189%. These findings provide a scientific foundation for exploring the host location mechanism of female G. pyloalis during oviposition and developing novel biological control technologies.

A hybrid laminar flow control (HLFC) airfoil with boundary-layer suction (BLS) applied between 50 and 80% of the chord on the upper surface is tested in a wind tunnel, revealing the potential of HLFC in the adverse pressure gradient region. The HLFC airfoil is designed for Re=1.67 million (55 m/s) through a numerical optimization framework for two-dimensional HLFC profiles. The wind-tunnel model is constructed from composite materials with a metallic insert enabling BLS. The suction panel consists of a thin, porous stainless-steel sheet with laser-drilled holes of 120 μm in diameter and a porosity of 0.9%. This porous surface is bonded to a multichamber suction system that allows independent control of the suction flow rate at four chordwise locations. Pressure measurements are used to compute Cl and Cd, while infrared thermography tracks the transition location. Flow meters monitor the suction flow rate. Experimental results demonstrate that BLS extends the laminar region by displacing the laminar separation bubble toward the trailing edge, thereby reducing drag. The application of laminar-flow suction reduces aerodynamic drag by 33% compared with the baseline configuration and by 20% when accounting for the energy cost of suction actuation.

Extreme wind events are responsible for significant human and economic losses, with low-rise buildings particularly affected during such events. The current wind load provisions are based on wind tunnel tests of rectangular building models conducted over the past four decades. However, modern buildings have evolved into complex plan shapes that are often hardly represented by simplified shapes in existing provisions. This study investigated the pressure distribution around buildings with nonrectangular plans. Seven models were constructed and tested in a large wind tunnel under simulated atmospheric boundary-layer conditions. The results indicate that the wall and roof pressure distributions can vary significantly from those of rectangular buildings. Owing to the increased number and complexity of corners, more separation zones are formed, leading to a higher likelihood of multiple simultaneous suction zones. A comparison with current wind provisions also revealed that, in several cases, the local and area-averaged pressures exceeded the recommended design guidelines. Further research is essential to develop a wind load database that encompasses a wider variety of building shapes and ultimately establishes nonrectangular building wind design guidelines.

A wind-tunnel test campaign was conducted to estimate the surface-pressure fluctuations on NASA’s Zephyr probe during its descent into the Venusian atmosphere. A 2%-scale model of the Zephyr probe was manufactured, instrumented with 18 microphones, and tested in two wind tunnels located in the Fluid Mechanics Laboratory of NASA Ames Research Center at velocities ranging from 13 to 48 m/s. Microphones were located to provide spectra of pressure fluctuations in regions with different flow characteristics, as well as for calculating various two-point statistics. Besides fluctuating surface-pressure measurements, hot-film velocity measurements as well as smoke–laser flow visualization were conducted to better understand the flow around the probe. The flow visualization showed three primary flow regimes: an attached turbulent boundary layer on the front; a region of separated flow upstream of the flared lip; and a large, separated wake at the rear. The acoustic spectra generally showed three different shapes corresponding to these flow regions, with the highest levels at the rear of the model and directly in front of the drag plate. The autospectra and cross spectra were used to determine Corcos model parameters and were passed on for vibroacoustic analysis of the probe and the science instruments inside.