A CFPD-FSI analysis of the impact of nasal hairs on airflow patterns, nasal resistance, and particle filtration in a realistic human nasal airway.

The nasal passages of bats that emit their echolocation call through their nostrils have adapted for sound emission as well as standard respiratory and olfactory functions. Rhinolophids, hipposiderids and rhinonycterids all use a high duty cycle (HDC) echolocation strategy. In this study we used computational fluid dynamics (CFD) to simulate airflow through models of the nasal passages of 12 members of Rhinolophoidea, with the aim of gaining a greater insight into how differences in nasal passage anatomy and echolocation strategy influence airflow. We also aimed to gain greater insight into the function of the unique strands housed in the rhinolophid nasal passage, by comparing models with the strands intact and digitally removed. We found that nasal passage anatomy (e.g., the presence or lack of an ethmoturbinal I projecting into the rostral part of the nasal chamber), not echolocation strategy (HDC vs. low duty cycle) appeared to influence simulated airflow patterns and rates. Further, our results revealed digital removal of the unique strands within the nasal passages of the rhinolophids resulted in a reduction in the overall pressure gradient across the nasal passage models and altered the airflow patterns. How this pressure gradient change influences either the functions of echolocation and/or respiration warrants further investigation.

In complex flows where motions at distinctly different speeds co-exist on the same plane, current optical flow (OF) methods preferentially track the slower component due to the small-motion assumption in OF algorithms. We overcome this limitation by balancing light intensity and applying per-pixel time-based high-pass filtering. We demonstrate this method using schlieren video of air motion generated by speech, where fast speech air flow co-exists with slower buoyancy flows from body heat-discrimination impossible with conventional OF. Our method extracted air flow patterns several centimetres from the mouth as a function of spoken sounds, with peak velocities in the English "pa" sound agreeing with CFD simulations. The method allows analysis of spatial and temporal variation in air velocity at distance from the speaker's lips, made by different sounds (phones). To do this, kymographs (space-time velocity plots) were generated and analysed using Generalized Additive Mixed-effect Models (GAMM). At 30 cm from the lips, statistical models showed higher predictive power ([Formula: see text]: 2.64%→7.57%), reduced complexity, and improved fit (fREML: 6.8E7→7.3E6, 89.3% residual reduction) compared to uncorrected data. The method is generalizable to any 3D optically accessible flow with motion predominantly in the image plane containing co-located high and low speed motions.

Wind-blown sand hazards are a major threat to the safe operation of railways in arid regions. To systematically investigate how different subgrade structures affect sand transport and deposition around railway tracks and slopes, wind tunnel experiments and lagrange three-dimensional numerical simulations were conducted to simulate the airflow patterns and sand transport processes under three typical structural conditions: full subgrades, full bridges, and subgrade-bridge transition sections. The results indicate that the airflow velocity within the model height exhibits a typical "W" distribution along the flow direction, with significant differences in flow disturbance intensity and sand accumulation patterns. The full subgrade structure induces the strongest airflow interference, resulting in the highest sand deposition on the windward slope, followed by the leeward slope, with the most severe accumulation occurring in the track area. When a train model is introduced, sand accumulation on the leeward slope increases, with the accumulation on the windward side reaching 87% of that on the leeward slope, and sand deposition on the track increases by approximately 57%. In contrast, the bridge structure demonstrates superior ventilation, resulting in the least sand accumulation on the track, although this increases by about 56% with the addition of a train. The transition section exhibits intense wind-sand interaction, with the amount of sand accumulation on the track falling between those for the subgrade and bridge structures, and consistently higher deposition on the windward side than the leeward side. After introducing a train, the sand accumulation on the track in the transition section becomes comparable to that for the bridge structure.

Pediatric olfactory development remains poorly understood, particularly regarding how age-related nasal morphological changes influence olfactory airflow dynamics and odorant transport. This study aimed to characterize age-dependent variations in olfactory airflow patterns and odorant distribution within the pediatric nasal cavity using computational fluid dynamics (CFD) analysis. Three-dimensional nasal cavity models were reconstructed from high-resolution sinus CT scans of 11 pediatric patients (ages 3-18 years) using Mimics Innovation Suite. CFD simulations of inspiratory airflow were performed using OpenFOAM with physiologically scaled, age- and sex-dependent flow rates. Odorant transport was modeled as a dimensionless passive scalar representing an inert, non-reactive tracer gas to analyze concentration dynamics and arrival times at the olfactory mucosa across age groups. The olfactory cleft volume and airflow generally followed an upward trend from early childhood until approximately 15 years of age, with more pronounced enlargement observed in late adolescence (15-18 years). Young children (3-6 years) demonstrated markedly reduced olfactory airflow delivery compared to late adolescents (15-18 years). Odorant transport analysis revealed prolonged arrival times and reduced peak concentrations at the olfactory mucosa in younger subjects, indicating that anatomical immaturity constrains olfactory efficiency in early childhood. Age-related nasal morphological development substantially influences olfactory airflow dynamics and odorant transport efficiency in children. These computational findings provide mechanistic insights into pediatric olfactory development and may inform clinical assessment strategies for childhood olfactory disorders.

Empty Nose Syndrome (ENS) is a rare and paradoxical complication often associated with aggressive turbinate reductions. Previous computational fluid dynamic (CFD) modeling has indicated that distorted nasal airflow patterns could contribute to ENS. However, no data have shown that aggressive turbinate reductions consistently lead to ENS. Retrospective case series. Tertiary. We retrospectively recruited 6 nasal obstruction patients who underwent turbinate reduction surgery, and performed total inferior and middle turbinectomies on all patients using a published virtual surgical simulator. We compared the CFD modeling results to that of patients' presurgery and postsurgery and published 27 ENS patients. As expected, the virtual turbinectomy significantly expanded nasal airway cross-sectional area, more than that of actual surgery (inferior: 0.9 ± 0.4 to1.8 ± 0.3 cm2, middle: 0.6 ± 0.3 to 1.0 ± 0.3 cm2, all P < .01); however, it does not create the same distorted nasal airflow patterns as seen in ENS patients, with no significant difference in nasal resistance after actual surgery (0.12 ± 0.04 Pa/mL*s) versus virtual surgery (0.10 ± 0.03 Pa/mL*s) nor ENS (0.11 ± 0.04 Pa/mL*s, all P > .05). However, all had significantly higher inferior wall shear force (WSF) distribution, an important indicator of air/mucosa stimulation, than that of ENS patients (baseline 54.0 ± 11.9%, surgery: 51.5 ± 15.1%; virtual: 46.5 ± 11.5%, P > .05; ENS: 32.2% ± 12.5%, P < .001). The opposite was seen for the middle turbinate region-WSF among all actual or virtual surgeries conditions was significantly lower than that of the ENS group (baseline: 36.1 ± 11.0%; virtual: 30.2 ± 13.1%; ENS: 43.8 ± 10.1%; all P ≤ .05). ENS cannot be solely attributed to aggressive turbinate reduction surgeries with various factors potentially playing a role.

This study presents the design, development, and acoustic characterisation of a tessellated polyform absorber composed of perforated panels (PPs) made from jute-reinforced rigid composites. A full factorial optimisation involving 72 combinations—spanning 12 geometric variants, six cavity depths, multiple perforation ratios, and orifice diameters—was conducted using impedance tube measurements. Integration of jute fleece within the backing cavity, combined with an L-tromino tessellation, enabled noise absorption (NAC ≥0.9) across 400–6300 Hz in a single modular structure. To explain deviations from the classical Maa model, the transfer matrix was progressively refined: T 1 accounted for orifice irregularities caused by jute-fibre fraying; T 2 incorporated additional damping from jute fleece in the cavity. CFD simulations were conducted to qualitatively examine the influence of tessellated geometry on local airflow patterns and edge-induced vortical structures around the L-tromino elements. The analysis highlights how geometric discontinuities influence local viscous interaction, supporting the proposed topology-driven acoustic design. The resulting tessellated polyform structure demonstrates high acoustic efficiency along with favourable mechanical strength and fire-retardant characteristics of SMC-based natural fibre composites. This integrated approach offers a sustainable, geometry-driven solution suitable for precision acoustic environments such as recording studios and controlled architectural spaces.

This study investigates the effects of vehicle air-conditioning parameters on cabin thermal environment and occupant comfort. Computational fluid dynamics and discrete particle simulations involving different inlet-vent angles, inlet relative humidity (RH) levels, and occupant counts were conducted to analyze airflow, temperature, and RH. Thermal comfort was assessed using predicted mean vote (PMV), predicted percentage of dissatisfied (PPD), equivalent homogeneous temperature, and mean age of air (MAA). As a result, the uniform airflow at a 30° inlet angle provided the best global thermal comfort based on PMV (0.49) and PPD (10.02), whereas a 0° inlet angle improved local comfort around the chest area. Maintaining an inlet RH of 40–50% enhanced overall thermal comfort. Increasing the occupant counts raised the average cabin temperature to 301.76 K (Case 9), while also affecting local airflow patterns and MAA distributions; the addition of rear-seat occupants increased the local temperature around the driver’s left hand. These findings provide practical guidance for vehicle heating, ventilation, and air-conditioning system design, indicating that ventilation strategies should consider global comfort indices, localized airflow, thermal patterns, and particle removal performance. Overall, this parametric study highlights the association between vehicle cabin conditions and thermal comfort, providing baseline data for digital twin–based adaptive ventilation systems.

This cross-sectional study examined the relationship between facial and nasal anatomical structures and air pollution–related respiratory morbidity across six major Nigerian cities representing each geopolitical zone: Lagos, Port Harcourt, Enugu, Abuja, Kano, and Maiduguri. A total of 1,200 adults aged 18–65 years with at least five years of residence were recruited through multi-stage sampling. Air pollution exposure was assessed using fixed-site monitors and seven-day personal sensors for PM2.5, PM10, NO₂, SO₂, and CO, integrated with GIS mapping. Facial and nasal anatomy was evaluated using 3D facial scans, low-dose CT imaging, and rhinomanometry, while respiratory health was assessed via spirometry, ATS questionnaires, and medical record review. Analyses included descriptive statistics, bivariate correlations, multivariate regression, GIS mapping, and computational fluid dynamics (CFD) simulations. Findings revealed that wider nasal cavities and larger cross-sectional areas reduced susceptibility to asthma, chronic bronchitis, and allergic rhinitis, whereas narrower passages and higher airflow resistance increased vulnerability. Northern cities exhibited nasal structures adapted to dusty, arid environments, while southern cities had narrower nasal cavities and higher respiratory morbidity despite effective deposition of coarse particles. CFD simulations confirmed that nasal morphology influenced airflow patterns and particulate deposition, supporting anatomical modulation of individual exposure risk. These results highlight the interaction between environmental and biological factors in determining respiratory health. Public health strategies should integrate air pollution control, targeted respiratory screening, and personalized interventions considering anatomical differences. Understanding how nasal and facial structures influence pollutant deposition can improve risk assessment and guide mitigation efforts in urban populations exposed to high levels of air pollution.

Photovoltaic (PV) systems are important for sustainable energy infrastructure, but their rapid deployment introduces complex fire dynamics that current regulations fail to address adequately. While existing standards focus on the electrical safety of individual components, they often neglect the risks arising from the interaction between the PV array and the building envelope. This review synthesizes current research on ignition mechanisms, thermal behavior, and the aerodynamic propagation of smoke to evaluate these overlooked hazards. A primary finding is that the interstitial space between the panel and the roof functions as a “heat trap,” significantly altering airflow patterns and accelerating flame spread even across fire-rated materials. The analysis further highlights that standard testing protocols do not sufficiently account for the urban dispersion of toxic combustion byproducts, such as hydrogen fluoride and volatile organic compounds. By evaluating recent advancements in Computational Fluid Dynamics (CFD) and helium-based surrogate testing, this paper demonstrates that accurate prediction of pollutant transport requires coupled modeling of wind effects and thermal buoyancy. The study concludes that ensuring urban fire resilience demands an evolution from component certification to integrated system assessments that include installation geometry, ventilation strategies, and environmental impact.

Objective:Dupilumab is a monoclonal antibody approved for treatment of chronic rhinosinusitis (CRS) with nasal polyps, yet literature is sparse regarding its precise effect on nasal airway patency and airflow patterns. This study applied Computational Fluid Dynamics (CFD) modeling to examine the relationship between the changes in nasal structures and aerodynamics and the changes in symptoms after dupilumab treatment.Methods:Twelve patients enrolled, completed the Sinonasal Outcomes Score (SNOT-22), as well as CT scans pre and 3 or more months post-dupilumab treatment. Patient-specific CFD models were constructed, and Lund-Mackay (LM) scores were calculated.Results:Nasal airway cross-sectional area (CSA) and airflow rate (AFR) in the middle and superior but not inferior meatuses significantly increased posttreatment (all p < 0.05). These increases correlated with SNOT-22 scores (CSA: r = 0.49, AFR: r = 0.41, p < 0.05), as well as with one question in SNOT-22, decreased sense of smell/taste (CSA: r = 0.32–0.54, AFR: r = 0.29–0.53, p < 0.05), which may explain previously reported rapid improvement in olfaction post-dupilumab. Surprisingly, nasal resistance did not significantly decrease posttreatment (p = 0.12) nor significantly correlate with symptom scores. LM scores significantly improved post-dupilumab (14.4 ± 6.3 to 9.8 ± 4.6; p < 0.05), with moderate residual inflammation. LM significantly correlated with SNOT-22 scores (r = 0.46, p < 0.05), but not with smell/taste complaints.Conclusion:The impact of dupilumab on nasal airway patency and airflow is not uniform. It is more pronounced in the middle and superior, but not inferior meatus. These unique regional changes significantly correlate with and potentially drive the improvement in patient symptoms.Level of Evidence:3.

Decoupled synergistic control of airborne infection risk and thermal comfort in open layout dental clinics: Integration of indoor airflow pattern, physical barrier, and air purifier.

The wing is one of the most critical components in an aircraft structure, as it directly contributes to the generation of lift, which enables flight. Without wings, an aircraft would be unable to produce lift or counter aerodynamic drag effectively. This study aims to analyze the lift and drag forces acting on a NACA 0012 airfoil under varying angles of attack and flow velocities. Two approaches were employed: numerical simulations using ANSYS Fluent to investigate airflow patterns and pressure distribution on the upper and lower surfaces of the airfoil, and experimental testing in a wind tunnel to validate and complement the findings. The experiments considered angles of attack of 0°, 3°, 6°, and 9°, with freestream velocities of 1 m/s and 3 m/s. The quantitative data collected include lift coefficient (CL), drag coefficient (CD), the relationships between CL–α, CD–α, and CL–CD, as well as pressure and velocity distributions from the CFD simulations. Both computational and experimental results indicate that increasing the angle of attack produces a significant change in the lift and drag characteristics of the airfoil. In conclusion, variations in the angle of attack have a substantial impact on the aerodynamic flow behavior around the airfoil and on the magnitude of the resulting lift and drag forces.

Stability, controllability, and maneuverability are critical factors for aircraft with short takeoff and landing distances, such as modern fighter aircraft and unmanned aerial vehicles. Delta wings are commonly employed in these aircraft due to their efficient aerodynamics, enabling high maneuverability, and performance at both low and high speeds. Nonslender wings are used for low-speed performance and agility, while slender wings offer reduced drag and are suited for high-speed operations. In flight, an aircraft encounters different airflow patterns including vortices that circulate from the higher-pressure lower side of the wing to the lower-pressure upper side, contributing to lift generation. However, as the angle of attack increases, the vortices can become unstable and fluctuate, resulting in induced drag. Understanding this phenomenon is crucial for developing highly stable and maneuverable aircraft. This essay focuses on studying vortex breakdown in delta wings with varying sweep angles and at different AOAs. The essay aims to validate experimental and numerical solutions from previous studies on the variation of vortex breakdown in both slender and nonslender delta wings using computational fluid dynamics. By examining vortex breakdown characteristics in different wing configurations, this essay aims to contribute to developing aircraft designs that prioritize stability and maneuverability.

Olfactory dysfunction (OD) secondary to chronic rhinosinusitis (CRS) significantly impairs quality of life by hindering the detection of warning signals and reducing nutritional satisfaction. CRS, a prevalent inflammatory condition, commonly leads to diminished or complete loss of smell. A substantial component of CRS-associated OD is conductive, stemming from impaired odorant delivery to the olfactory neuroepithelium. The tools for assessing conductive OD range from clinical evaluations like endoscopy and CT scoring of the olfactory cleft to objective measures of nasal patency and advanced computational fluid dynamics modeling. The underlying conductive mechanisms are multifactorial, primarily involving two interrelated pathways: alterations in nasal airflow dynamics due to anatomical variations or obstructive lesions, and pathological changes in the physicochemical properties of olfactory cleft mucus. Obstructions from septal deviation, turbinate hypertrophy, nasal polyps, and mucosal edema within the olfactory cleft disrupt and redistribute inspiratory airflow, critically reducing odorant access. Concurrently, inflammation-driven changes in the olfactory mucus—including hypersecretion, ionic imbalance, and deficiencies in odorant-binding proteins and metabolizing enzymes—impair odorant transport, solubilization, and signal transduction. Current therapeutic strategies, such as endoscopic sinus surgery and corticosteroids, aim to relieve these conductive barriers but may offer only partial or temporary benefit, highlighting the need for precise phenotyping. A systematic, individualized assessment of both airflow patterns and mucus properties is crucial for understanding the conductive contribution and predicting outcomes. This review synthesizes current evidence on the conductive mechanisms of olfactory loss in CRS, evaluating the impact of nasal aerodynamics and mucus alterations, and discusses integrated management strategies for this debilitating condition.

Introduction: Dry powder inhalers (DPIs) are essential for pulmonary drug delivery, enabling efficient and precise deposition of drugs in the lungs. Optimizing DPI performance re-quires an in-depth understanding of the aerosolization process, including airflow dynamics and particle behavior, although patient variability remains a challenge in developing new inhaler types. This review examines the application of computational fluid dynamics (CFD) for analyz-ing and improving DPI function. Methods: A comprehensive literature review was conducted using PubMed, Scopus, and Web of Science, covering articles published from 2010 to 2025. Studies focusing on CFD modeling of airflow, particle dispersion, and deagglomeration in DPIs were selected based on predefined eli-gibility criteria. Screening was conducted at the title, abstract, and full-text stages. Results: The investigations indicate that CFD accurately models airflow patterns, pressure dif-ferentials, and particle trajectories in DPI devices. CFD methodologies vary in turbulence mod-els, boundary conditions, and particle tracking techniques. Significant findings include enhanced predictions of aerosol dispersion and insights into how device shape influences medication deliv-ery efficacy. Discussion: The findings underscore the growing significance of CFD in DPI research. CFD en-ables virtual prototyping, reduces the need for extensive experimental testing, and supports the optimization of inhaler design. Limitations include the complexity of precisely modeling particle and particle-wall interactions, as well as the requirement for experimental validation. Conclusion: CFD has proven to be an effective computational tool for examining the aerosoliza-tion mechanisms of DPIs. Its application facilitates the development of more efficient, patient-centric inhalation therapies by improving design accuracy and performance reliability.

Understanding particle deposition patterns in the pulmonary acinus is essential for early intervention and treatment in acinar diseases. This study numerically investigated the effects of respiratory modes and emphysematous alveolar wall ablation on airflow and particle deposition in a physiologically representative pulmonary acinar model. A heterogeneous acinar model was developed, incorporating alveolar expansion and contraction via the dynamic meshing method, and its validity was confirmed by comparison with published particle deposition data. Airflow and particle transport patterns were then analyzed under varying respiratory modes and degrees of alveolar wall ablation. For particles smaller than 1 μm, deposition decreased with higher breathing frequency and increased with larger tidal volume. Smaller particles penetrated deeper and deposited more uniformly due to strong airflow coupling. Compared with the normal acinus, the lesioned acinus exhibited reduced airflow variability, lower expansion capacity, and a decreased deposition fraction. Alveolar wall ablation impaired lung expansion and restricted distal airflow penetration, leading to localized particle deposition near the acinar entrance. As lesion severity increased, the deposition progressively declined due to altered flow patterns and a reduced surface-to-volume ratio. The particle deposition declined nonlinearly with lesion severity. A 30% wall ablation reduced total deposition by over 40%, whereas further increases to 60% and 90% caused only minor additional decreases, indicating a nonlinear response in which early structural damage disproportionately affects acinar particle deposition. These findings underscore the importance of early intervention to preserve alveolar drug deposition efficiency and improve therapeutic outcomes in patients with progressive pulmonary diseases such as emphysema.

Urban ventilation is an effective means of improving air quality and promoting sustainable development of urban areas. For Loess Tableland valley towns dependent on heavy industry, the ventilation characteristics of the town area are poorly understood. Therefore, it is important to first explore wind field characteristics over the negative terrain. In this study, the wind field over the negative terrain under the stable background wind was investigated by orthogonal experiments. Simulation results show that airflow patterns in the valley space can be classified into five categories, which are the unstructured flow, combination of unstructured flow and circulation organization, circulation organization, combination of circulation organization and background wind and background wind. The airflow pattern can affect significantly the vertical distribution of the velocity, temperature and air age in the valley space, and thus affecting the ventilation performance of the valley towns. Ventilation performance of valley towns was worse under the unstructured flow conditions, while it was optimal under the background wind conditions. Additionally, sensitivities of terrain factors influencing ventilation evaluation indices at the pedestrian level were analysed. The present study has provided a scientific basis for town planning and industrial emissions in the valley towns.

Indoor airflow effect on the detectability of airborne pathogens: Simulation with computational fluid dynamics and validation with field PCR measurements.

The role of natural ventilation in long-range airborne transmission in a hospital respiratory ward: A Monte Carlo simulation