Search Results (240)

Thin liquid film evaporation leverages latent heat and low thermal resistance to achieve superior heat transfer capabilities, making it pivotal for next-generation high-heat-flux thermal management systems. This paper presents a systematic review of the fundamental mechanisms, interfacial transport behaviors, and experimental techniques associated with static thin films and falling liquid films. This work elucidates the complex coupling of Marangoni convection, van der Waals disjoining pressure, and contact line dynamics. These mechanisms collectively govern film stability and the intensity of non-equilibrium phase change in the micro-region. The influence of surface wettability and dynamic contact angle hysteresis on hydraulic replenishment and dry spot formation is critically analyzed, offering insights into optimizing surface engineering strategies. In addition, the review categorizes advanced non-intrusive diagnostics, including optical interferometry, laser-induced fluorescence (LIF), and infrared thermography, evaluating their capacity to resolve spatiotemporal variations in film thickness (ranging from 10 nm to several μm) and temperature under complex boundary conditions. Special attention is directed toward falling film evaporation over horizontal tubes, addressing flow regime transitions and the impact of interfacial shear from external airflow. The work concludes by identifying key challenges in multi-physics coupling and proposing future directions for synchronized diagnostics and adaptive surface design. Full article

Air quality management in greenhouses is critical to safeguarding plant health and occupational safety, yet conventional filtration methods often fall short in performance and sustainability. These enclosed environments are prone to the accumulation of bioaerosols, including fungi, bacteria, pollen, and dust particles, which can compromise crop productivity and pose health risks to workers. This review explores recent advancements in air filtration technologies for controlled environments such as greenhouses, where airborne particulate matter, bioaerosols, and volatile organic compounds (VOCs) present ongoing challenges. Special focus is given to the development of filtration media based on electrospun nanofibers, which offer high surface area, tunable porosity, and low airflow resistance. The use of biodegradable polymers in these systems to support environmental sustainability is examined, along with electrospinning techniques that enable precise control over fiber morphology and functionalization. Antimicrobial enhancements are discussed, including inorganic agents such as metal nanoparticles and bio-based options like essential oils. Essential oils, known for their broad-spectrum antimicrobial properties, are assessed for their potential in long-term, controlled-release applications through nanofiber encapsulation. Overall, this paper highlights the potential of integrating sustainable materials, innovative fiber fabrication techniques, and nature-derived antimicrobials to advance air filtration performance while meeting ecological and health-related standards. Full article

Background/Objectives: Patients with eosinophilic chronic obstructive pulmonary disease (COPD) often remain symptomatic despite optimized triple inhaled therapy. Dupilumab is a fully human monoclonal antibody that blocks the IL-4 receptor alpha subunit, thereby inhibiting IL-4 and IL-13 signaling. Evidence from randomized trials supports dupilumab for add-on treatment of type 2-high COPD, but data referring to short-term effectiveness in clinical practice are quite limited. Methods: We conducted an observational, compassionate-use study enrolling 13 consecutive outpatients with eosinophilic COPD (blood eosinophils ≥ 300 cells/µL) receiving add-on biologic therapy with dupilumab 300 mg every two weeks. Clinical (CAT, mMRC), functional (spirometry and body plethysmography), and inflammatory parameters (blood eosinophils/basophils, fibrinogen, FeNO) were evaluated at baseline and after four weeks of treatment. Safety was monitored after injection in a clinical setting, as well as via weekly phone follow-up. Results: Participants (84.6% male; mean age 67.08 ± 11.42 years) experienced rapid and clinically meaningful improvements at four weeks. CAT score decreased from baseline 21.40 ± 6.22 to 14.00 ± 5.58 (p < 0.001) and mMRC scale from 2.90 ± 0.73 to 1.80 ± 0.63 (p < 0.0001), respectively. Pre-bronchodilator FEV₁ increased from baseline 1.35 ± 0.65 L to 1.59 ± 0.84 L (p < 0.05), and FVC from 2.36 ± 0.92 L to 2.83 ± 1.11 L (p < 0.01). A marked lung deflation was observed: indeed, residual volume declined from baseline 4.17 ± 1.98 L to 3.47 ± 2.07 L (p < 0.05), with a concomitant reduction in specific effective airway resistance (from baseline 3.15 ± 1.77 to 2.43 ± 1.44 kPa·s; p < 0.05) associated with significant increases in mid-expiratory flow (FEF₂₅₋₇₅: from baseline 0.62 ± 0.38 to 0.86 ± 0.71 L/s; p < 0.05) and peak expiratory flow (3.80 ± 1.40 to 4.48 ± 1.79 L/s; p < 0.01). Type 2 inflammatory biomarkers changed as follows: blood eosinophil count fell from baseline 390.0 ± 43.75 to 190.0 ± 65.47 cells/µL (p < 0.001); blood basophil number decreased from baseline 37.50 ± 13.89 to 26.25 ± 13.02 cells/µL (p < 0.001); plasma fibrinogen lowered from baseline 388.4 ± 54.81 to 334.9 ± 72.36 mg/dL (p < 0.01); FeNO levels dropped from baseline 23.95 ± 18.10 to 14.00 ± 2.04 ppb (p < 0.0001). Dupilumab was well tolerated, and no treatment-related serious adverse events or discontinuations were detected. Conclusions: Within an exploratory context of daily medical activity referring to eosinophilic COPD already treated with maximal inhaled therapy, we found relevant therapeutic effects of a four-week add-on treatment with dupilumab. In particular, our patients manifested rapid improvements in symptoms, airflow limitation, and lung hyperinflation, paralleled by significant decrements of type 2 inflammatory signatures. Such encouraging results were associated with a favorable short-term safety profile. However, larger and longer studies are necessary to corroborate these preliminary findings. Full article

Flow sensing is essential in biomedical engineering, industrial process control, and environmental monitoring. Conventional sensors, while accurate, are often constrained by high fabrication costs, complex processes, and limited design flexibility, restricting their use in disposable or rapidly customizable applications. This paper presents a novel ultra-low-cost airflow sensor fabricated entirely through fused deposition modeling 3D printing. The device employs a cantilever-based structure printed with PETg filament, followed by the deposition of a conductive ABS piezoresistive layer in a two-step process requiring no curing or post-processing. Experimental characterization reveals that the sensor operates in an ultra-low pressure range of 0.88–26.68 Pa, corresponding to flow velocities of 1.2–6.6 m/s. The sensor achieves a sensitivity of 967 Ω/Pa, a resolution of 9.27 Pa, and a detection limit of 83.27 Pa, with a total resistance change of approximately 51.5 kΩ. This kilo-ohm-scale response enables direct readout via a digital multimeter without requiring Wheatstone bridges or instrumentation amplifiers. The minimalist design, combined with sub-5 min fabrication time and material cost below $0.05, positions this sensor as an accessible platform for disposable, scalable, and resource-constrained flow monitoring applications in both biomedical and industrial contexts. Full article

Horizontal well air sparging (HAS) technology provides a promising approach for pollution remediation. In this study, a model experiment assessed the airflow distribution characteristics of HAS under varying air sparging (AS) pressure, tube burial depth, and groundwater flow conditions, while evaluating the retardation effects of HAS on dissolved groundwater contaminants. The results indicated that airflow velocity and diffusion range increased markedly with elevated AS pressure. Deeper AS tube burial depths resulted in more uniform airflow distribution and broader coverage. Groundwater flow significantly affected airflow distribution, as greater water head differences induced a downstream shift in the airflow pattern, resulting in an asymmetric diffusion range. Regarding pollutant retardation, airflow created a physical barrier by reducing permeability and interfacial resistance, effectively hindering pollutant diffusion. Airflow from the AS tube aligned parallel to the flow direction reduced Rhodamine B concentration by 53.1% over 300 min, preventing deeper pollutant migration into the sand layer. Conversely, airflow from the AS tube oriented perpendicular to the flow direction reduced Rhodamine B concentration by 84.38% over the same period, demonstrating superior effectiveness in limiting horizontal pollutant diffusion. These findings provide valuable theoretical insights and practical guidance for implementing HAS technology in groundwater pollution management. Full article

Nowadays, in order to follow the trends and principles of sustainability, natural materials are often investigated in acoustics and noise prevention. Hemp fibre is a sustainable alternative to conventional sound-absorbing or insulating materials. The aim of the research is to investigate the acoustic properties of different types of hemp fibre. Five different types of hemp fibre were tested: bleached, cottonized, boiled cottonized, well-stripped decorticated, and short, not combed decorticated fibres. The hemp fibre samples were varied in thickness from 20, 40, and 60 mm and density from 50 to 250 kg/m³ in steps of 50 kg/m³. The sound transmission loss of the material was measured using an impedance tube. In order to predict the sound absorption properties of the samples, the airflow resistivity of the hemp fibre was determined. Based on the theoretical calculations proposed by Delany, Bazley, and Miki, a theoretical analysis of the sound absorption of hemp fibre was performed. In order to determine the dependence on different fibre types, all fibres were examined using SEM. It has been found that hemp fibre can be used as an insulating or sound-absorbing material in noise prevention, as a sustainable alternative to conventional materials. Full article

Predicting the thermo-physiological comfort of technical clothing requires an understanding of how microscopic textile structures influence macroscopic properties such as air, heat, and moisture permeability. This work represents the first step towards a multi-scale predictive tool capable of estimating key comfort-related properties from the geometrical features of woven fabrics. Focusing on air permeability, the effect of structural and design parameters was investigated while keeping the fibre material (cotton) constant. A computational framework that combines validated Computational Fluid Dynamics (CFD) simulations with a Fully Connected Neural Network (FCNN) was developed, enabling fast and accurate predictions before production. The CFD model accounts for both intra- and inter-yarn porosity, ensuring reliability across a wide range of fabric configurations. The FCNN, trained on simulation and literature data, achieved a mean absolute relative error of 2.01% and a maximum error of 7.72%, demonstrating excellent agreement with experimental results. The analysis highlights how weave type and yarn density govern airflow resistance, offering an efficient tool for the design and optimisation of breathable technical textiles. Full article

In naturally ventilated dairy barns, many questions regarding airflow, indoor air quality, and emissions are still unanswered, often resulting in inaccurate environmental control of the housing. Particularly, limited understanding of the implications of the constantly changing outdoor weather conditions in interaction with the building design and the role of the characteristics of the animals’ movement inside the building enhances uncertainties in the estimation of airflows within and across the barns. Computational fluid dynamics (CFD) have been used in the past to better understand the dynamics of barn climate, but the models are typically too slow to be used for real-time prediction and control. We investigated the effect of animal characteristics (i.e., animal location, orientation, body posture, and dimensions) on the pressure drop in the animal occupied zone considering inlet wind speed from 0.1 m s⁻¹ to 5 m s⁻¹ and wind direction of 0° and 90° in a CFD model. The cow position in general had little impact on the pressure drop at low wind speeds, but became relevant at higher wind speeds. Cows distributed in a more organized alignment showed less airflow resistance, and, therefore, a lower pressure drop and higher air velocities. Moreover, the cow breed affected the pressure drop, with higher withers resulting in a higher pressure drop and air resistance. In contrast, the effects of cow lying–standing ratio on the pressure drop and airflow resistance coefficients were negligible for both investigated wind directions. Our study aims to provide guidance for optimizing parametrizations of the animal occupied zone in order to enhance the speed of simulations without significant loss in model accuracy. In addition, the conclusions drawn from our study may support the adaption of building design and herd management to improve the effectiveness of ventilation concepts of naturally ventilated dairy barns. Full article

Dry heat inactivates pathogens on personal protective equipment without chemical residues, but its effects on material integrity and performance across multiple reprocessing cycles have not been comprehensively assessed. We evaluated five filtering facepiece respirator (FFR) models and three surgical mask (SM) models after one, two, and three cycles of dry heat (80 °C, 90 min). We measured fabric and strap tensile properties as indicators of mechanical durability [Young’s modulus (E), yield strength (σ_y), ultimate tensile strength (σ_UTS), and strain at failure (ε_f)]. We also assessed particle filtration efficiency (PFE) and airflow resistance (breathability). Under the methods applied herein, all untreated SMs and FFRs performed within the range anticipated for their type. Tensile properties exhibited heterogeneous, model-specific responses to thermal stress. FFR fabrics ranged from progressive stiffening (Dräger DR-X1720C; +120% E) to marked softening (3M-8210; −82% E), while SM fabrics exhibited softening, consistent with thermal relaxation. Straps made of thermoplastic elastomer (3M-8210 and 3M-9320A+) weakened (15–31% σ_UTS decrease), whereas braided polyisoprene straps (3M-1860S and 3M-1870+) maintained their original strength. Despite these changes, all treated FFR replicates met filtration requirements across all cycles (45/45). For SMs, 24/27 treated replicates met the required PFE threshold (≥98%), but 3 treated RH-S919B replicates fell below this threshold (PFE 94.9% and 97.7% after one cycle, and PFE 97.3% after three cycles), identifying a potential model-specific vulnerability to the treatment. Breathability remained within control ranges for most models; however, the Level 2 ZA-S001B showed decreased breathability (higher airflow resistance) after two (+11.1 Pa) and three (+13.3 Pa) dry-heat cycles, whereas the Level 3 RH-S920TFG showed modest improvements in breathability (lower airflow resistance, up to −10.1 Pa). Under these laboratory conditions, up to three cycles of dry heat at 80 °C for 90 min preserved PFE and breathability in all treated FFR replicates and in most treated SM replicates. Nonetheless, there were measurable, component-specific mechanical changes (especially in some straps) that could compromise fit and durability with repeated use. These findings support dry heat at 80 °C for 90 min as a potential component of emergency PPE processing strategies, provided that model-specific quantitative fit testing and extended-wear studies confirm safe real-world reuse, regulatory approvals are met, and end-user acceptability is considered. Full article

L-shaped tunnels frequently occur in underground coal mines because of geological and operational limitations. Their complex geometry increases ventilation resistance and causes non-uniform airflow, promoting combustible gas accumulation and resulting in a greater fire risk than in straight tunnels. In this work, Fire Dynamics Simulator was employed to quantify the effects of the fire source’s transverse position, curvature radius, heat release rate, and imposed longitudinal ventilation on both the critical velocity and the extent of smoke back-layering. The analysis shows that higher heat-release rates elevate the critical velocity, whereas a centrally located fire yields the lowest value. Shifting the fire toward either sidewall or adopting a larger curvature radius results in a higher critical velocity. In addition, the extent of upstream smoke back-layering increases with curvature, peaking when the ignition point lies close to the convex sidewall. Specifically, with a ventilation velocity of 0.95 m/s and a centerline fire, the back-layering length extends from 23 m ($R$ = 5 m) to 40 m ($R$ = 10 m). Based on theoretical derivation and dimensional analysis, several dimensionless parameters were developed that incorporate both the transverse fire-source position and the curvature radius to modify the dimensionless heat-release rate. Finally, dimensionless predictive models for the critical velocity and back-layering length, incorporating the effects of the curvature radius and the fire transverse position, were developed. These models provide a theoretical foundation and practical framework for fire prevention and ventilation design in L-shaped tunnels. Full article

Airflow regulation is essential for optimizing pesticide deposition in orchard spraying. This study developed an airflow attenuation model for a five-port air-assisted sprayer by integrating jet dynamics with crown resistance characteristics. The tree crown was modeled as a porous medium with calibrated resistance coefficients, and airflow attenuation was described using momentum conservation theorems, with initial conditions derived from jet decay profiles at the outlet. Validation included free-space airflow measurements and field trials in three fruit tree species. In free-space tests, the model showed a maximum relative error of 22.31% and a mean error of 12.26%. Field tests yielded a maximum error of 25.92%, with mean errors of 14.85% and 15.76% at 2300 and 2800 rpm, respectively. The model provides a theoretical basis for intelligent airflow control aimed at improving deposition and reducing drift. Full article

Poultry transport represents a significant animal welfare challenge, particularly when birds are exposed to heat stress during travel, a condition that can compromise physiological stability, performance, and survival. Despite the relevance of this issue, research on engineering improvements to poultry transport crates remains limited. In this study, four virtual models of poultry transport crates were evaluated to assess their potential to improve the thermal comfort internal airflow conditions. Computational Fluid Dynamics (CFD) simulations were conducted under three transport speeds, complemented by wind tunnel experiments using reduced-scale prototypes fabricated by additive manufacturing. The results demonstrated that the alternative crate 3 (AC3) model presented exhibited superior internal average airflow velocities (IAFV) across all speeds, including a 32.85% increase compared to the conventional crate at 60 km/h. Wind tunnel testing confirmed significant differences among crate designs. AC3 showed lower air temperature than AC1 and reduced relative humidity compared to CC and AC2. Thermal comfort indices supported these findings, with AC3 presenting the lowest THI and enthalpy, indicating a less stressful microclimate. In terms of airflow, AC2 and AC3 achieved higher IAFV (19.27 ± 8.49 m/s and 19.30 ± 4.80 m/s) than CC and AC1. AC3 also had the lowest dynamic pressure, suggesting reduced airflow resistance and more efficient aerodynamics. Therefore, improved crate geometry and increased ventilation surface can enhance airflow distribution, potentially reduce heat accumulation and improve animal welfare. However, further studies involving live birds, realistic stocking densities, and full-scale trailer simulations are required to validate these benefits under commercial transport conditions. Full article

This study examines the impact of vocal fold (VF) lesions located on the superior surface on glottal airflow dynamics and tissue oscillatory behaviors using biomechanical simulations of a two-layered realistic VF model. It is hypothesized that morphological changes in the VFs due to the presence of a lesion cause changes in tissue elasticity and rheological properties, contributing to dysphonia. Previous research has lacked the integration of lesions in computational simulations of anatomically accurate larynx-VF models to explore their effects on phonation and contribution to voice disorders. Addressing the current gap in literature, this paper considers a computational model of a two-layered VF structure incorporating a lesion that represents a hemorrhagic polyp. A three-dimensional, subject-specific, multilayered geometry of VFs is constructed based on STL files derived from a human larynx CT scan, and a fluid–structure interaction (FSI) methodology is employed to simulate the coupling of glottal airflow and VF tissue dynamics. To evaluate the effects of the lesion’s presence, two FSI models, one with a lesion embedded in the cover layer and one without, are simulated and compared. Analysis of airflow dynamics and tissue vibrational patterns between these two models is used to determine the impact of the lesion on the biomechanical characteristics of phonation. The polyp is found to slightly increase airflow resistance through the glottis and disrupt vibratory symmetry by decreasing the vibration frequency of the affected fold, leading to weaker and less rhythmic oscillations. The results also indicate that the lesion increases tissue stress in the affected fold, which agrees with clinical observations. While quantitative ranges depend on lesion size and tissue properties, these consistent and physically meaningful trends highlight the biomechanical mechanisms by which lesions influence phonation. Full article

Passenger cars, sports utility vehicles (SUVs), and light trucks/vans, constituting the overwhelming majority of all road vehicles globally, burn about 25% of all fossil fuels, emit significant amounts of greenhouse gas emissions (CO₂), and deteriorate the environment. Nearly three-quarters of the engine power generated by burning fossil fuels is required to overcome aerodynamic resistance (drag) at highway driving speeds. Streamlining the body shape, especially the projected frontal area, can lead to a decrease in aerodynamic drag. Even though drag coefficients have plateaued since the late 1990s, further altering body shape might worsen vehicle cooling. Thus, the primary objective of this study is to explore the potential for aerodynamic drag reduction and improved cooling performance through careful component design unaffected by stylistic restraints. A variety of strategies for protecting the cooling intakes to reduce the drag coefficient are considered. The potential cooling drag reduction was found to be around 7% without compromising the cooling performance, which is in line with predictions for roughly 2.9% and 1.7% fuel consumption reductions for highway and city driving conditions, respectively. The study also reveals that passenger electric cars designed for city driving conditions possess a battery-to-kerb weight ratio of around one-quarter of the kerb weight, and vehicles designed for higher ranges have significantly higher ratios (nearly one-third), resulting in higher rolling resistance and energy consumption. The reduction of battery weight for EVs, streamlining vehicle shapes, and applying active and passive airflow management can help reduce aerodynamic drag and rolling resistance further, enhance driving range, and reduce energy consumption and greenhouse gas emissions. Full article

Background: Tracheal breathing sounds (TBS) have demonstrated strong potential as a non-invasive, wakefulness-based diagnostic tool for obstructive sleep apnea (OSA); yet the relationship between specific upper airway anatomical features and the resulting TBS spectra remains insufficiently understood. This study aims to enhance the diagnostic utility of TBS in OSA by investigating how the upper airway anatomy influences TBS spectral characteristics. Method: Patient-specific computational models of the upper airway were reconstructed from high-resolution CT scans of a healthy subject and an individual with OSA. Additional variants were generated with targeted constrictions at the velopharynx, oropharynx, and trachea, based on clinically reported anatomical ranges. Airflow dynamics were simulated using Large Eddy Simulation (LES), and the resulting acoustic responses were computed via Lighthill’s acoustic analogy within a hybrid aero-acoustic framework. Results: Oropharyngeal constriction generated the most spatially concentrated vorticity patterns among single-region constricted models. Airway Resistance analysis revealed that severe velopharyngeal and oropharyngeal constrictions contributed most to regional airway resistance. Spectral analysis showed that velopharyngeal narrowing produced a progressive downward shift in the third resonance peak (1000–1700 Hz), while oropharyngeal narrowing induced an upward shift of the third peak and a downward shift of the fourth peak (1700–2500 Hz). These frequency shifts were attributed to the effective role of acoustic mass and airway compliance. Conclusions: Anatomical modifications of the upper airway produce region-specific changes in both flow and acoustic responses. These findings support the use of TBS spectral analysis for non-invasive localization of airway obstructions in OSA. Full article