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An experimental study to investigate the flow of liquid jet issued from a high aspect ratio nozzle slit into an incoming airflow by changing the orientation angle from the incoming free-stream was performed. A two-dimensional liquid sheet emerged from the narrow slit into the subsonic air crossflow. Different orientation angles between 0 and 90 degrees were studied. High-speed photography and shadowgraphy techniques were utilized to visualize the flow physics. The influence of the slit orientation angle on the flow morphology and the flow regimes of liquid sheets was investigated. Some fluid flow parameters were obtained by analyzing the images. The changes in breakup height of different orientations were measured. A model was offered for the breakup height of the liquid sheet based on the liquid-to-gas momentum ratio, gas Weber number, and a new non-dimensional parameter as a representation of the angle of slit orientation. Also, the defined sheet trajectory for each orientation angle was obtained, and the variations were examined. Empirical correlations for the defined trajectory of the sheet in terms of liquid to gas momentum ratio and gas Weber number for each orientation angle were proposed. [ABSTRACT FROM AUTHOR]

Bats rely on their hand-wings to execute agile flight maneuvers, to grasp objects, and cradle young. Embedded in the dorsal and ventral membranes of bat wings are microscopic hairs. Past research findings implicate dorsal wing hairs in airflow sensing for flight control, but the function of ventral wing hairs has not been previously investigated. Here, we test the hypothesis that ventral wing hairs carry mechanosensory signals for flight control, prey capture, and handling. To test this hypothesis, we used synchronized high-speed stereo video and audio recordings to quantify flight and echolocation behaviors of big brown bats (Eptesicus fuscus) engaged in an aerial insect capture task. We analyzed prey-capture strategy and performance, along with flight kinematics, before and after depilation of microscopic hairs from the bat's ventral wing and tail membranes. We found that ventral wing hair depilation significantly impaired the bat's prey-capture performance. Interestingly, ventral wing hair depilation also produced increases in the bat's flight speed, an effect previously attributed exclusively to airflow sensing along the dorsal wing surface. These findings demonstrate that microscopic hairs embedded in the ventral wing and tail membranes of insectivorous bats provide mechanosensory feedback for prey handling and flight control. [ABSTRACT FROM AUTHOR]

The application of turbulators to improve thermal performance and thermal enhancement in heat exchangers because of the significance of energy management and optimization is one of the interesting topics for researchers. Analysis of aerodynamic turbulator in internal flow has been less discussed in previous studies. Therefore, the present work focuses on the effect of a perforated sphere turbulator in a circular pipe with square, circular, oval, and hexagonal geometry holes on turbulent flow characteristics and thermal performance. These turbulators are placed with equal obstruction against the flow of air passing inside the pipe at Re = 6000–24000 in wall conditions of constant heat flux. Ansys Fluent software is used for numerical solutions, and the results are validated with an experimental paper. According to the results, the hexagonal geometry creates less pressure drop than other geometries. The thermal performance in the pipe with innovative aerodynamic turbulators is improved compared to the smooth pipe and the pipe equipped with conventional turbulators. The highest thermal performance of 1.256 is obtained for the turbulator with an oval hole. Also, the range of Nusselt number compared to the plain pipe for turbulator with circular, hexagonal, square, and oval holes increases by 1.97–2.46, 2.24–2.65, 1.58–1.89, and 2.48–2.81 times, respectively. The effect of the proposed new turbulators was compared with previous studies in this field, and the results are promising. [ABSTRACT FROM AUTHOR]

The projected speckle-based three-dimensional digital image correlation method (3D-DIC) is being increasingly used in the reliability measurement of microelectronic packaging structures because of its noninvasive nature, high precision, and low cost. However, during the measurement of the thermal reliability of packaging structures, the thermal airflow generated by heating introduces distortions in the images captured by the DIC measurement system, impacting the accuracy and reliability of noncontact measurements. To address this challenge, a thermal airflow distortion correction model based on the transformer attention mechanism is proposed specifically for the measurement of thermal warpage in microelectronic packaging structures. This model avoids the oversmoothing issue associated with convolutional neural networks and the lack of physical constraints in generative adversarial networks, ensuring the precision of grayscale gradient changes in speckle patterns and minimizing adverse effects on DIC calculation accuracy. By inputting the distorted images captured by the DIC measurement system into the network, corrected images are obtained for 3D-DIC calculations, thus allowing the thermal warpage measurement results of the sample to be acquired. Through experiments measuring topography with customized step block specimens, the effectiveness of the proposed method in improving warpage measurement accuracy is confirmed; this is particularly true when captured images are affected by thermal airflow at 140 °C and 160 °C, temperatures commonly encountered in thermal reliability testing of packaging structures. The method successfully reduces the standard deviation from 9.829 to 5.943 µm and from 12.318 to 6.418 µm, respectively. The results demonstrate the substantial practical value of this method for measuring thermal warpage in microelectronic packaging structures. [ABSTRACT FROM AUTHOR]

The unsteady airflow will cause the distortion and delay change of the signal propagation path, resulting in the delay and distortion of the received satellite signal. This will lead to increased ranging and direction finding errors in the positioning system, which will affect the precision and accuracy of the positioning results. Therefore, a new multi-satellite anti-interference hybrid positioning method under the influence of unstable airflow is studied. Preprocess the unstable turbulence data at high altitude, and verify the turbulence data authenticity quickly. The flow field description equation is constructed based on the momentum conservation theorem. The multi-satellite motion equation is established by using the carrier phase observations and satellite antenna phase center coordinates, and the anti-interference hybrid positioning model is constructed. Global Navigation Satellite System (GNSS) technology is introduced to solve the multi-satellite hybrid anti-interference model by using the signals of multiple satellites to calculate the receiver's position, speed and time. The experimental results show that, for static targets, the research method has a small deviation in the positioning of the target N, S and E. When using the mixed positioning of near-earth satellite, medium altitude satellite and geosynchronous satellite, the mean square value of positioning error is always lower than 0.002 cm. For the dynamic target, the method is not disturbed by clutter, and the target is stably located. Moreover, the proposed method has lower localization delay and higher localization efficiency. [ABSTRACT FROM AUTHOR]

Photovoltaic (PV) panels are similar in many aspects to the leaves of trees, both are standing in the Sun to capture the sunlight, however, PV panels get soiled especially in desert areas, while the leaves remain clean to a very good extent. The question is, why leaves remain clean while PV panels get soiled quite easily? The leaves are hanging on the stem of trees and these stems are flexible to motion, such that if the wind blows in any direction over the stem it vibrates allowing any deposited particle to fall off the surface. The objective of this research is to develop a fixation method for PV panels similar to the stems of trees, such that the panel can vibrate as the wind blows in order to minimize dust accumulation. Different fixation methods for the PV panel are designed, and the air flow around the panel is simulated using the CFD package Ansys Fluent. It has been found that a PV panel pivoted at its lower edge, such that it can revolve around the lower edge, together with a vertical wind shield attached to its upper edge and a spring attached at the middle of its backside has the largest vibration amplitude due to the applied wind compared to the other designs. Experiments have been done to infer the influence of the new fixation method of the PV panel on dust accumulation over the panel. After 6 weeks of operation, it has been found that the efficiency of the PV panel that is flexibly fixed has dropped by only 5%, while the efficiency of the panel that is rigidly fixed has dropped by 25%. It can be concluded that a PV panel operating a light post should be fixed on a flexible base that allows the panel to vibrate as the wind blows over it in order to mitigate dust. [ABSTRACT FROM AUTHOR]

The aim of this research is to conduct an experiment that will evaluate the effect of combining of counter flow air-impinging arrangement and an arc-shaped turbulators over the absorber plate of solar heater. This combination is intended to improve the thermohydraulic performance of the solar air heater. The parameters such as energy transfer and frictional factor are studied at flow Reynolds number varies from 18,000 to 3600, and the influence of a hole jet bore ratio from 0.0430 to 0.109 is considered. At the optimal hole jet bore ratio of 0.0650, the thermo-hydraulic achievement parameter has a value of 1.75, which is the greatest possible value can be attained. When compared to multi-pass V and multiple V roughened solar air heaters based on the THAP, the current work is improved the performance by 55.3 and 32.9%, respectively. Such comparisons clearly demonstrate the superiority of the present work. Furthermore, a relationship is shown between the jet hole bore ratio and the thermohydraulic performance measure, with a maximum divergence of 10%. [ABSTRACT FROM AUTHOR]

Odours used by insects for foraging and mating are carried by the air. Insects induce airflows around them by flapping their wings, and the distribution of these airflows may strongly influence odour source localisation. The flightless silkworm moth, Bombyx mori, has been a prominent insect model for olfactory research. However, although there have been numerous studies on antenna morphology and its fluid dynamics, neurophysiology, and localisation algorithms, the airflow manipulation of the B. mori by fanning has not been thoroughly investigated. In this study, we performed computational fluid dynamics (CFD) analyses of flapping B. mori to analyse this mechanism in depth. A three-dimensional simulation using reconstructed wing kinematics was used to investigate the effects of B. mori fanning on locomotion and pheromone capture. The fanning of the B. mori was found to generate an aerodynamic force on the scale of its weight through an aerodynamic mechanism similar to that of flying insects. Our simulations further indicate that the B. mori guides particles from its anterior direction within the ~ 60° horizontally by wing fanning. Hence, if it detects pheromones during fanning, the pheromone can be concluded to originate from the direction the head is pointing. The anisotropy in the sampling volume enables the B. mori to orient to the pheromone plume direction. These results provide new insights into insect behaviour and offer design guidelines for robots for odour source localisation. [ABSTRACT FROM AUTHOR]

Electric motors with high-power densities are required for the implementation of electromobility. To achieve this, direct liquid cooling methods are increasingly being considered, in which oil is injected into the motor compartment. This results in a two-phase flow that can be used for efficient cooling. However, the oil, which can also penetrate the air gap between the rotor and stator, can also lead to additional losses due to increased friction. Since little is known about the two-phase flow in such systems, especially in the air gap, it is investigated by means of simple optical visualizations and high-speed laser-induced fluorescence imaging as well as torque measurements. The measurements are carried out in the air gap of an optically accessible generic model of a directly cooled electric motor. Speed variations were performed from 100 to 2000 rpm, and three different two-phase flow regimes were observed. At low speeds (Flow Regime 1), the air gap is filled locally with oil in radial direction, in the medium speed range (Flow Regime 2) with foam, while at high speeds (Flow Regime 3) separated films were observed on the rotor and stator. The torque difference between the two-phase and single-phase operation, which quantifies the mechanical losses due to the injected oil, increased continuously due to the oil in the air gap until it reached a maximum in Flow Regime 2 due to foam formation. In Flow Regime 3, the torque difference was negative. This was attributed to the fact that the grooves in the stator were filled with oil, thus reducing the turbulence generation of the air flow. [ABSTRACT FROM AUTHOR]

Atmospheric convection across the northern inter-Americas is modulated by trade-wind subsidence and subtropical easterly waves from June to October. Northward migration of the equatorial trough is coupled to the meridional circulation (MC) and surface temperatures above 27ºC. Forming a MC index via S-N height sections of total and anomalous streamfunction, statistical relationships are examined which focus on Jun-Oct season when the South American monsoon is quiescent. Both east Pacific and tropical north Atlantic exhibit cool ocean – dry atmosphere response to an intensified MC. During periods of faster MC, composite humidity is depleted over the Caribbean 10–25 N in conjunction with westerly wind shear, thereby limiting atmospheric convection. The ocean response to intensified MC is evaporative cooling and a deep layer of increased salinity in the Caribbean, that may sustain anomalous air-sea interactions. Long-term trends reveal intensification of the MC in boreal summer: rising over the Amazon, subsiding over the Caribbean, inter-connected by lower and upper airflows. The annually pulsed MC conspires with inter-decadal trends to produce many of the features presented. [ABSTRACT FROM AUTHOR]

Part of the gaseous carbon dioxide (CO2) produced in karst soils / epikarst is transported into underground cavities / caves during the growing season by advective flux, diffusive flux, and flux associated with degassing of seeping water. In dynamic caves, accumulated CO2 is released into the outside atmosphere during the autumn-winter period through advective flux associated with ventilation of the cave in the upward airflow mode. This case study from the Moravian Karst (MK) showed that the net weight of CO2 released annually from the Sloup-Šošůvka Caves (total volume of 131,580 m3 and a total area of 17,950 m2) into the external atmosphere was 348 kg. Extrapolating this value to all known MK caves (area about 352,080 m2) yielded a total of CO2 flux of 6820 kg yr−1. This flux is representing only 0.024‰ of the annual soil respiration from entire MK area (about 2.81 × 108 kg CO2 yr−1). [ABSTRACT FROM AUTHOR]

Proton Exchange Membrane Fuel Cells (PEMFCs) used in Unmanned Aerial Vehicles (UAVs) have an important place in the aviation industry and mostly operate under high current density conditions. Notably the operating temperature, the fuel supply pressure and volumetric flow rates of air and fuel can be counted among the important parameters that affect the high current density. Therefore, a comprehensive optimization analysis becomes inevitable. In present study, it is aimed to optimize the operating conditions that are considered to be effective on the current density of a PEMFC, by applying the well-known Taguchi Design of Experiment (DoE) method. Current density values of a selected PEMFC have been calculated by MATLAB/Simulink commercial software. The number of simulations is determined by Taguchi method. The most suitable orthogonal array L18, is utilized to identify the optimal factor conditions. The contribution ratio of each parameter on the current density is revealed by Analysis of Variance (ANOVA). The confirmation is supplied by confirmation tests. The optimum values for the current density are obtained when the operating temperature is 313 K, the fuel flow rate is 50 lpm, the air flow rate is 300 lpm and the fuel supply pressure is 1.5 bar. The contribution ratios of cell temperature, supply pressure, flowrate of fuel and flowrate of air are, respectively, found to 69.7%, 16.6%, 6.7% and 0.9%. [ABSTRACT FROM AUTHOR]

Because of the lack of good seedling positioning during vegetable grafting, there are issues such as high labor costs and long grafting time. This article proposes a negative pressure suction seedling positioning method for seed leaves based on the characteristic parameters of cucumber spike wood, and designs a flexible adsorption positioning mechanism for spike wood. Firstly, the ventral surface curve trajectories of cucumber cotyledons were extracted using Matlab software, and then a shape-adaptive design was applied to the attachment surface of the flexible suction positioning mechanism, and a computational fluid dynamics model of the airflow field was established. By combining Fluent simulation analysis with orthogonal experiments, the effect of suction hole diameter, vacuum negative pressure value, suction hole quantity, and suction hole depth on the adsorption effect of the suction head was analyzed, the main and secondary factors and operational indicators that affect the adsorption effect are evaluated. The optimal parameter combination: suction hole diameter of 1.5 mm, vacuum negative pressure value of 2 kPa, suction hole quantity of 42, and suction hole depth of 2 mm, has been found. A verification experiment was conducted on a test bench, and the experimental results show that the success rate of leaf absorption using the optimal parameter combination is 97.69%, which indicates that the suction head is designed reasonably and meets the requirements of grafting. [ABSTRACT FROM AUTHOR]

Obstructive sleep apnea (OSA) is an airway disease caused by periodic collapse of the airway during sleep. Imaging-based subject-specific computational fluid dynamics (CFD) simulations allow non-invasive assessment of clinically relevant metrics such as total pressure loss (TPL) in patients with OSA. However, most of such studies use static airway geometries, which neglect physiological airway motion. This study aims to quantify how much the airway moves during the respiratory cycle, and to determine how much this motion affects CFD pressure loss predictions. Motion of the airway wall was quantified using cine MRI data captured over a single respiratory cycle in three subjects with OSA. Synchronously-measured respiratory airflow was used as the flow boundary condition for all simulations. Simulations were performed for full respiratory cycles with 5 different wall boundary conditions: (1) a moving airway wall, and static airway walls at (2) peak inhalation, (3) end inhalation, (4) peak exhalation, and (5) end exhalation. Geometric analysis exposed significant local airway cross-sectional area (CSA) variability, with local CSA varying as much as 300%. The comparative CFD simulations revealed the discrepancies between dynamic and static wall simulations are subject-specific, with TPL differing by up to 400% between static and dynamic simulations. There is no consistent pattern to which static wall CFD simulations overestimate or underestimate the airway TPL. This variability underscores the complexity of accurately modeling airway physiology and the importance of considering dynamic anatomical factors to predict realistic respiratory airflow dynamics in patients with OSA. [ABSTRACT FROM AUTHOR]

Metallic microfluidic devices made from powder-bed additive manufacturing systems have received increasing attention, but their feasible channel geometry and complexity are often limited by lack of an effective approach to removing trapped powder particles within the channels or conduits of the sintered parts. Here, we present an innovative approach to fabricating long serpentine, high-aspect-ratio submillimeter channels made of stainless steel 316L (SS) by binder jet printing (BJP) and liquid-phase sintering. We leverage the unique nature of the BJP process, that is printing and consolidation steps are decoupled, enabling us to join two or more parts during the sintering step. Instead of constructing the channel device as a single part, we print multiple parts for easy powder removal and later join them to form enclosed channels. The key innovation lies in adding sintering additives like boron nitrides (BN) to the SS stock powder—at the SS/BN interfaces, liquid phase is locally generated at temperature much lower than the SS melting temperature, facilitating the bonding of the multiple parts as well as the consolidation of parts for near-full density. We systematically vary the sintering temperature to show how it affects the joining quality and the channel shape distortion. The joining quality such as the fracture strengths of the joined samples is measured by a pull test while the shape distortion is characterized by various imaging techniques. The feasibility of the proposed approach is demonstrated by fabricating a 400-mm-long, fully enclosed serpentine channel with a rectangular cross-section of 0.5 mm in width and 1.8 mm in height. The pressure drop across this 3D-printed SS serpentine channels is measured for air flow and compared to a standard gas flow model, showing that the device is free of leakage or clogs. [ABSTRACT FROM AUTHOR]

This work presents a novel approach to investigating the slip effect in nanofiber filter media. Electrospun nanofiber media with high efficiency and low pressure drop were produced at different concentrations and durations. The surface and cross-sectional morphology of nanofiber media were studied using FE-SEM. Fiber orientation and diameter distributions were also examined. The 3D virtual nanofiber media was modeled using this information along with the experimentally measured porosity and thickness of the media. The effect of the slip phenomenon in nanofiber media was studied numerically, and the results were compared to experimental data. Excellent agreements were found between the measured and simulation results. Additionally, filtration simulations considering aerosols injected with airflow through the nanofibrous filter media were conducted by considering the slip effect, and the effect of filter structure on filtration performance (removal efficiency and pressure drop) was investigated. [ABSTRACT FROM AUTHOR]

Background: Obstructive sleep apnea (OSA) is a prevalent sleep breathing disorder affecting 9–25% of the general adult population. Aim: To assess airflow limitation by spirometric indices in patients with obstructive sleep apnea. Patients and methods: This observational case–control study was conducted on 60 subjects who were divided into four groups: Group I (control group), included 20 subjects chosen from other departments, who had no respiratory complaints with apnea–hypopnea index (AHI < 5); Group II (mild group), included 11 patients with mild sleep apnea, 5 ≤ AHI < 15; Group III (moderate group), included 17 patients with moderate sleep apnea, 15 ≤ AHI < 30; and Group IV (severe group), included 12 patients with severe sleep apnea, AHI ≥ 30 at the Chest Department, Faculty of Medicine, Helwan University, from August 2021 until June 2022. Results: There was no statistically significant relation found between the severity of AHI and all the previous pulmonary function parameters except a statistically significant decrease in FEF (25–75%) in the moderate group than the mild group and also in the severe group than the moderate group (p-value < 0.001). There was a statistically significant positive correlation found between AHI and BMI and NC and a negative correlation found between AHI and FEF (25–75%) while no statistically significant correlation was found between AHI and the other studied parameters. Conclusion: Obstructive sleep apnea (OSA) is associated with airflow limitation by spirometric indices, although this association is statistically insignificant. On the other hand, the severity of obstructive sleep apnea is directly proportional to the seriousness of the apnea–hypopnea index (AHI). Strong correlations were found between the severity of AHI and body mass index (BMI), neck circumference, and FEF (25–75%). [ABSTRACT FROM AUTHOR]

The control of oxygen and carbon dioxide concentrations in an airflow released from a reactor, in which a sample is heated, can be used to investigate the thermal stability of polymer materials. This approach, known as oxithermography, involves analyzing experimental data (oxithermograms), representing the variation in oxygen concentration decrease and carbon dioxide appearance in an airflow with changing temperature conditions. This method allows for monitoring the effect of fillers introduced into polymer compositions on their thermal stability. The application of oxithermography to studying oxidative thermostability is demonstrated using pure polypropylene and polypropylene with titanium dioxide admixtures as examples. [ABSTRACT FROM AUTHOR]

A promising mathematical model is considered for studying the aeroelastic stability of sandwich shells supported by an internal hollow elastic cylinder and annular ribs. Using the relations derived, the influence of thickness of the inner hollow cylinder, the length of the shell, and the shear modulus of core on the critical air flow speed leading to the occurrence of flutter was studied. Based on the calculations performed, recommendations were developed for choosing parameters of the sandwich composite structure considered. The mathematical model presented makes it possible to expand the range of topical scientific and applied problems that can be solved in the field of aeroelastic stability of sandwich shells. [ABSTRACT FROM AUTHOR]

The small-scale desalination system known as humidification-dehumidification (HDH) operates on the principles of low-grade energy compatibility and simple design. The air in a bubble column becomes more humidified due to a combination of factors such as the liquid's height, thermophysical properties, air mass flow, and flow characteristics like bubble size. The designed HDH unit can be utilized to provide cooling water with low conductivity to reactors. An experimental setup and a theoretical model are developed to study the Humidification-Dehumidification (HDH) system's performance in a co-current direct-contact condenser spray column (CDCC). The designed HDH unit in the present study can be utilized to provide cooling water to the reactors. A novel use of nanofluid is introduced for enhancing the humidification of air in bubble columns. The addition of copper oxide nanoparticles to water-base fluid to form nanofluid in the bubble column humidification can increase the thermal conductivity and the viscosity of the suspensions. The impact of copper oxide nanofluid (CuO, 99%, 40 nm) in the bubbling column and air temperature were studied. The experiment's findings indicate that, at a humid air temperature of 45 °C, the condensate flow rates are nearly twice as high when utilizing CuO-water nanofluid as when using water. With nanofluid, the average product from HDH is higher than with water, around 34% in theory and 29% in experiment. The inlet temperature of hot humid air has a significant effect on the condensate product. When the temperature of humid air rises from 45 to 70 °C, the product increases more than four times at constant mass fluxes of cooled spray water and hot humid air. Results show that, for various humid air outlet temperatures, the nanofluid raises the absolute humidity of the humid air in the bubbling column filled with CuO-water nanofluid. When using nanofluids instead of water, the HDH system's effectiveness is improved by 4% in humidifiers and 8% in dehumidifiers. There is good agreement between experimental measurements and theoretical predictions for the HDH system. [ABSTRACT FROM AUTHOR]

In this study, both the optical and piezoelectric properties of polyvinylidene fluoride (PVDF) electrospun nanofibers were investigated at different needle-to-collector distances of the electrospinning process at constant applied high voltage. For piezoelectric characterization, the fabricated nanofiber mats were subjected to applied forces, including cyclic force, variable frequency-based loads, and free-falling masses (impulse loading), along with power density analysis for different load resistance values. In addition, both optical absorbance and transmittance measurements were conducted to evaluate the optical properties of the fabricated nanofibers. The piezoelectric analysis demonstrated the best piezoresponse of the fabricated nanomats at a needle-to-collector distance of 15 cm and high voltage of 22 kV. However, a trade-off between piezoelectric response and optical transmissivity was observed based on the electrospinning distance parameter. The relatively higher optically transparent sample exhibited only moderate piezoelectric response, while the less transparent sample displayed the highest piezoelectric activity. Based on the optimized sample and piezoelectric analysis, the synthesized nanofiber mat was subjected to applied mechanical stress in the form of variable velocity and momentum loads. A maximum potential of approximately 16 V was harvested through velocity and momentum impact, especially with the addition of a double-layer PVDF membrane. Furthermore, the sensing effect of airflow pressure on single/double-layer PVDF was studied. The single-layer PVDF membrane generated 79 mV under an airflow speed of 21 km/h, while the double-layer membrane produced 114 mV potential under the same airflow. This study highlights the diverse applications of PVDF nanofiber mats as multifunctional sensors and energy harvesting applications from mechanical shocks and airflow impact. [ABSTRACT FROM AUTHOR]

Snow avalanche run-out is controlled by flow regime, which is heavily dependent on snow temperature and water content. Existing avalanche models calculate temperature change and snow melting arising from frictional work, snowcover entrainment and particle collisions, but ignore the influence of the ambient air temperature. Here, we propose an experimentally-based relationship to describe the sensible heat flux between the flowing avalanche and the ambient air. A snow avalanche case study and a sensitivity analysis are performed using the proposed model. Modeling results suggest a marginal contribution of heat to the avalanche core, but one, that nonetheless can have significant effect on avalanche runout. For wet (warm) avalanches, higher air temperature will amplify water lubrication effects, leading to longer avalanche run-out. Warmer air temperatures also influence the behaviour of dry, cold avalanches, as the presence of meltwater increases snow cohesion, restricting the formation of strong powder clouds and reducing the avalanche run-out. Colder air temperatures facilitate the formation of more fluidized powder snow avalanches with long run-out and strong air-blasts. The proposed model quantifies the temperature change in the avalanche and can be included in avalanche hazard assessments in which temperature and flow regime are important elements, including the understanding of air temperature and avalanche flow in a changing climate. [ABSTRACT FROM AUTHOR]

The impacts of hydrometeor-related processes on the development and evolution of the "21·7" extremely heavy rainfall in Zhengzhou were investigated using WRF simulations. Surface precipitation was determined by the hydrometeor microphysical processes (all microphysical source sink terms of hydrometeors) and macrophysical processes (local change and flux convergence of hydrometeors). The contribution of hydrometeor macrophysical processes was commonly less than 10%, but could reach 30%–50% in the early stage of precipitation, which was largely dependent on the size of the study area. The macrophysical processes of liquid-phase hydrometeors always presented a promotional effect on rainfall, while the ice-phase hydrometeors played a negative role in the middle and later stages of precipitation. The distributions of microphysical latent heat corresponded well with those of buoyancy and vertical velocity (tendency), indicating that the phase-change heating was the major driver for convective development. Reasonable diagnostic buoyancy was obtained by choosing an area close to the convective size for getting the reference state of air. In addition, a new dynamic equilibrium involving hydrometeors with a tilted airflow was formed during the heavy precipitation period (updraft was not the strongest). The heaviest instantaneous precipitation was mainly produced by the warm-rain processes. Sensitivity experiments further pointed out that the uncertainty of latent heat parameterization (±20%) did not significantly affect the convective rainfall. While when the phase-change heating only altered the temperature tendency, its impact on precipitation was remarkable. The results of this study help to deepen our understanding of heavy rainfall mechanisms from the perspective of hydrometeor processes. [ABSTRACT FROM AUTHOR]

Coronaviruses being capable of spreading through droplet contamination have raised significant concerns regarding high-capacity public rail transport, such as the metro. Within a rapidly moving railcar cabin, the internal airflow lags behind the bulkhead, generating internally induced airflow that accelerates droplet dispersion within a non-inertial reference system. This study investigates the impact of acceleration on the diffusion of cough droplets of varying sizes using computational fluid dynamics. The modified k–ε equation in ANSYS® Fluent was utilized to simulate droplet diffusion under different body orientations by adjusting the inertial force correction source term. Results indicate that droplets in the middle size range (50–175 μm) are primarily influenced by inertial forces, whereas smaller droplets (3.5–20 μm) are predominantly controlled by air drag forces. Regardless of facial orientation, the outlet of high-capacity public rail transport poses the highest risk of infection. [ABSTRACT FROM AUTHOR]

When the lightweight quartz fiber-reinforced phenolic (LQFRP) composite is subjected to the combined effect of a local structural heat source and high-speed airflow, its ablation behavior exhibits significant localized characteristics and strong coupled effect. In this study, we have developed a bidirectional loosely coupled numerical model that integrates thermal, fluid, solid and ablation phenomena to solve the ablation-through problem of the LQFRP composite. The model takes into account the mechanisms of pyrolysis, oxidation, sublimation, and thermal mechanical erosion that occur during the ablation process of the LQFRP composite. The results suggest that the local structural heat source plays a crucial role in the erosion and retreat of the LQFRP composite. The morphology of the ablation pit shows a noticeable asymmetry, which is attributed to the aerodynamic heat and force. As a result of the local structural heat source, the fluid temperature downstream of the ablation pit is higher compared to that upstream of the ablation pit. The fluid that flows downstream of the ablation pit undergoes significant compression, leading to the formation of an oblique shock wave. The distribution of resin pyrolysis degree within the LQFRP composite is influenced by internal heat conduction. This study will offer valuable insights and guidance for the practical application of the LQFRP composite in the ultra-high temperature field. [ABSTRACT FROM AUTHOR]

Desalination, which converts saline water into freshwater, has been proposed as a possible alternative to address the worldwide freshwater scarcity problem. The humidification–dehumidification (H–DH) desalination technique can provide appropriate quantity of freshwater to the population residing in water-stressed regions. The aim of the current study is to investigate the solar H–DH desalination system performance which consists of a solar air heater based on double-ends open evacuated tube collector, a packed bed humidifier, and a dehumidifier. The packing material used in humidifier is aspen pads. The performance is assessed based on system overall efficacy, gained output ratio (GOR), yield, and efficacy of humidifier and dehumidifier at three distinct process air flow rates. The average overall system efficacy, yield, and GOR are 11.97%, 4.1 kg day-1, and 0.84, respectively, for open-loop system. The closed-loop system reports better performance at low mass flow rate. The average overall system efficiency, daily yield, and GOR at 100 kg h−1 are 32.48%, 11.9 kg day-1, and 2.44, respectively, for a closed-loop system. [ABSTRACT FROM AUTHOR]

In this work, the performance of an inline dimpled-based absorber plate solar air heater (IDPSAH) is studied in relation to pitch, a system parameter, and air flow rate (Mair), an operating parameter. In this regard, two alternative IDPSAH with pitch ratios 0.88 and 1.33 have been experimentally evaluated on alternative days by altering the Mair from 0.010 to 0.053 kg s-1 (Proportional Re range: 1971.66–11,113.24) and the result are compared with flat plate solar air heater (FPSAH). For performance evaluation and comparative research, various parameters have been studied, including air temperature difference, efficiencies (ηinst, ηeff, ηdaily), global heat loss coefficient, heat removal factor, collector efficiency, top loss, area averaged Nusselt number (Nuavg), and friction factor (favg), among others. The effective efficiency reaches its maximum at a particular Mair and then begins to decline, but the instantaneous and daily efficiency of IDPSAH and FPSAH increases continuously. Due to a decrease top loss, the efficiency of IDPSAH is higher than FPSAH. The instantaneous efficiency of IDPSAH at pitch ratio 0.88 is 1.13–1.53 times greater than the instantaneous efficiency of IDPSAH at pitch ratio 1.33 and it is 1.21–1.86 times higher than FPSAH. With an increase in Re, the favg value decreases; while, the Nuavg of both the FPSAH and IDPSAH increases. In comparison with IDPSAH with pitch ratio 1.33, the Nuavg of IDPSAH at pitch ratio 0.88 is 1.23–1.41 times higher, and it is 1.68–2.12 times higher than FPSAH. In comparison with IDPSAH at pitch ratio 1.33 and FPSAH, the favg of IDPSAH at pitch ratio 0.88 is higher. However, there is a significant enhancement in overall performance of IDPSAH than the FPSAH. [ABSTRACT FROM AUTHOR]

Breaking laminar sub-layer and creating turbulence flow is the main characteristic of solar air heater to increase heat transfer. Several geometries have been employed, and their effect on heat transfer has been studied by researchers. These effects are studied in form of Nusselt number (Nu) and friction factor (Fr) rise and correlations for them are developed. In current experimental study, a novel geometry in shape of rhombus is used as roughness. Rhombus shape is selected because of its feature of v shape and converging nature on its end sides which helps to guide the flow of air and offer more secondary flow and less resistance. The geometrical and flow parameters are varied as number of elements (W/Vr), relative diagonal length (dr/e), Reynolds number (Re), relative roughness height (e/Dh), relative roughness pitch (P/e) within range of 8–12, 6–13.33, 2500–14200, 0.0202–0.0337 and 6–14, respectively. Variation of 258–378% and 215–148% more compared to smooth plate is achieved for Nu and Fr, respectively. Nu increases when values of P/e increases and attains maxima at P/e = 10, e/Dh = 0.03375, W/Vr = 10 and dr/e = 9.6. Experimental correlations are grounded in actual data making them applicable to real-world scenarios and practical applications. The deviation between Nu and Fr calculated from the correlation and experimentation was ± 12% and ± 10%, respectively. [ABSTRACT FROM AUTHOR]

Excellent mechanical and electric properties enable the piezoelectric materials to be widely and dynamic aero-mechanical-electric coupling properties of the piezoelectric plate structures can significantly affect performance of aircrafts flying in high speed. This paper is focused on the flutter behaviors of the functionally graded piezoelectric material (FGPM) plate in supersonic airflow. The first-order shear deformation theory (FSDT) is employed to formulate the energy functional of the FGPM plate with general boundary conditions. The supersonic air flow is taken into account using the supersonic piston theory. The governing equations for the aero-mechanical-electric coupling system are deduced on basis of the Hamilton's principle. To address the limitation of intricate boundary conditions to the admissible functions, a modified Fourier series is introduced to yield the unified solutions of the FGPM plate subject to supersonic airflow and with arbitrary boundary conditions. Flutter properties of series of FGPM plates are investigated to demonstrate robust ability of the proposed method to accurately yet consistency include the aero-elastic-electric coupling, inhomogeneous material and arbitrary boundary conditions. The influences of the boundary condition, material constituent, external voltage and yawed flow angle on the vibration, and flutter behaviors of the FGPM plate are examined. Adjusting corresponding parameters accordingly can significantly improve the stability of the plate structures subject to supersonic airflow, which provides physical insights into dynamic optimal design of the plate structures. [ABSTRACT FROM AUTHOR]

The current paper experimentally studied the performance of solar-driven internally cooled liquid desiccant system for hot and humid climates using CaCl2 as a liquid desiccant. The system is designed to investigate the input conditions of the room by adjusting various air and solution variables. This internally cooled liquid desiccant system consists of the dehumidifier and regenerator in a single module and the regeneration of the solution is done by solar energy. The present study analyzes the effect of solution concentration, air mass flow rate and solution volume flow rate using different performance indices such as humidity reduction, moisture effectiveness, enthalpy effectiveness, and COP. The results demonstrate that the maximum moisture reduction of 4.2 g/kg d.a. is found at an airflow rate of 0.03195 kg/s, a solution volume flow rate of 12.5 LPM, and a solution concentration of 37%, while the maximum COP of 0.274 is obtained at an airflow rate of 0.0715 kg/s, a solution volume flow rate of 12.5 LPM, and a solution concentration of 37%. The maximum moisture and enthalpy effectiveness are obtained as 24.1% and 26.2%, respectively. The paper also presents the correlations for moisture and enthalpy effectiveness based on findings from experiments. [ABSTRACT FROM AUTHOR]

This study explores the structure, modulation, and impacts of the mean diurnal climate across southeast Africa using high-resolution hourly reanalysis and satellite rainfall. This research was motivated by upward trends in diurnal temperature range and vegetation index over the Drakensberg escarpment. Statistical analysis identified a land-sea rainfall dipole pattern associated with diurnal airflows. Point-to-field regressions (Oct–Mar 2000–2023) found that sea breeze-driven convection is underpinned by 'col' airflow between adjacent sub-tropical low-pressure cells (30°S, 20°E/22°S, 37°E) and a weak mid-latitude anticyclone (40°S, 10°E). Diurnal residual and case study analysis demonstrate an ~ 6-m/s sea breeze penetrating ~ 200 km inland during the day, as part of an over-turning zonal circulation. Land > sea rainfall during summer is initiated by temperature gradients ∂T/∂x ~ 5 °C at 29°S, 31°E and convergence in the afternoon ∂U/∂x ~ − 4 × 10−5 s−1. Further inland (29°S, 26°E) a 1007-hPa thermal low and counter-clockwise rotating airflows interact with the incoming sea breeze. Together these contribute to evening rainfall ~ 30 mm over the Drakensberg escarpment. The drivers of diurnal rainfall show little response to global climate variability, and help sustain water resources during multi-year dry spells over southeastern Africa. [ABSTRACT FROM AUTHOR]

Objectives: To report the outcomes of pediatric patients who underwent allogeneic hematopoietic stem cell transplant (HSCT) in single rooms without high-efficiency particulate air (HEPA) filters, laminar air flow or positive pressure at our centre and discuss the adaptations of a high-volume government centre. Methods: Data of the first 20 children who underwent allogeneic HSCT between May 2019 and July 2023 in adaptive settings were reviewed retrospectively. All patients were managed in in single rooms without HEPA filters, positive pressure or laminar air flow. Supportive care in the form of antimicrobial prophylaxis, veno-occlusive disease prophylaxis, anti-epileptics (with busulfan) and irradiated blood products were provided. Trained manpower including multi-specialty consultations were readily available. All complications including infections were managed as per standard guidelines. Results: The median (range) of children included was 6 (1–20) years. For eight patients we used alternate donors. The mean (SD) time to neutrophil and platelet engraftment were 17.0 (8.07) days and 18.8 (10.1) days, respectively. The mean (SD) time to discharge from the hospital was 30.9 (10.04) days. There were no deaths within 30 days. Six children each developed acute and chronic graft-versus-host disease (GVHD). The overall survival at a median follow-up of 292 days was 70% (n = 14). Conclusions: With certain adaptations in the existing infrastructure in resource-limited settings, allogeneic HSCT can be performed with good outcomes, provided experienced, dedicated and adequate personnel, comprehensive supportive care, multidisciplinary consultative support and isolation are provided. [ABSTRACT FROM AUTHOR]

The issue of sensitivity attenuation in high-pressure region has been a persistent concern for pressure-sensitive electronic skins. In order to tackle such trade-off between sensitivity and linear range, herein, a hybrid piezoresistive-supercapacitive (HRSC) strategy is proposed via introducing a piezoresistive porous aerogel layer between the charge collecting electrodes and iontronic films of the pressure sensors. Surprisingly, the HRSC-induced impedance regulation and supercapacitive behavior contribute to significant mitigation in sensitivity attenuation, achieving high sensitivity across wide linear range (44.58 kPa−1 from 0 to 3 kPa and 23.6 kPa−1 from 3 to 12 kPa). The HRSC pressure sensor exhibits a low detection limit of 1 Pa, fast responsiveness (~ 130 ms), and excellent cycling stability, allowing to detect tiny pressure of air flow, finger bending, and human respiration. Meanwhile, the HRSC sensor exhibits exceptional perception capabilities for proximity and temperature, broadening its application scenarios in prosthetic perception and electronic skin. The proposed HRSC strategy may boost the ongoing research on structural design of high-performance and multimodal electronic sensors. [ABSTRACT FROM AUTHOR]

To study the characteristics of nasal airflow in the presence of nasal cycle by computational fluid dynamics. CT scan data of a healthy Chinese individual was used to construct a three-dimensional model of the nasal cavity to be used as simulation domain. A sinusoidal airflow velocity is set at the nasal cavity entrance to reproduce the breathing pattern of a healthy human. There was a significant difference in the cross-sectional area between the two sides of the nasal cavity. Particularly, the decongested side is characterized by a larger cross-section area, and consequently, by a larger volume with respect to the congested side. The airflow velocity, pressure, and nasal resistance were higher on the congested narrow side. The temperature regulation ability on the congested narrow side was stronger than that on the decongested wider side. During the nasal cycle, there are differences in the nasal cavity function between the congested and decongested sides. Therefore, when evaluating the impact of various factors on nasal cavity function, the nasal cycle should be considered. [ABSTRACT FROM AUTHOR]

Mycotoxin production by aflatoxin B1 (AFB1) -producing Aspergillus flavus Zt41 and sterigmatocystin (ST) -hyperproducer Aspergillus creber 2663 mold strains on corn and rice starch, both of high purity and nearly identical amylose-amylopectin composition, as the only source of carbon, was studied. Scanning electron microscopy revealed average starch particle sizes of 4.54 ± 0.635 µm and 10.9 ± 2.78 µm, corresponding to surface area to volume ratios of 127 1/µm for rice starch and 0.49 1/µm for corn starch. Thus, a 2.5-fold difference in particle size correlated to a larger, 259-fold difference in surface area. To allow starch, a water-absorbing powder, to be used as a sole food source for Aspergillus strains, a special glass bead system was applied. AFB1 production of A. flavus Zt41 was determined to be 437.6 ± 128.4 ng/g and 90.0 ± 44.8 ng/g on rice and corn starch, respectively, while corresponding ST production levels by A. creber 2663 were 72.8 ± 10.0 µg/g and 26.8 ± 11.6 µg/g, indicating 3–fivefold higher mycotoxin levels on rice starch than on corn starch as sole carbon and energy sources. Key points: • A glass bead system ensuring the flow of air when studying powders was developed. • AFB1 and ST production of A. flavus and A. creber on rice and corn starches were studied. • 3–fivefold higher mycotoxin levels on rice starch than on corn starch were detected. [ABSTRACT FROM AUTHOR]

For people with respiratory disorders who need additional oxygen therapy, oxygen concentrators are vital medical equipment. By concentrating oxygen from the ambient air, they function to give the user a greater flow of oxygen-enriched air. The application of lithium zeolite for oxygen concentration in POCs is the most intense part of this work. One kind of zeolite material that may selectively absorb nitrogen from the air to increase oxygen concentration is lithium zeolite. The capacity, effectiveness, and dependability of a POC fitted with lithium zeolite are all examined in this study, along with its overall performance. The findings show that lithium zeolite, which has benefits including high oxygen purity and low energy consumption, is a potential material for use in POCs. The results of this study aid in the creation of POCs for oxygen therapy that are more effective and efficient. This study suggests utilizing an Arduino microcontroller and an HX710B air pressure sensor to measure the oxygen flow rate in a POC. The POC's oxygen flow channel incorporates the HX710B sensor to monitor pressure variations, which the Arduino uses to translate into flow rate readings. To verify the accuracy and dependability of the system, its performance is assessed under different flow rate scenarios. Lithium zeolites are well-known for having a high selectivity for nitrogen adsorption, which can enhance the concentrator's oxygen separation process's effectiveness. Lithium-zeolite-based oxygen concentrators may have a lower environmental effect than standard concentrators. [ABSTRACT FROM AUTHOR]

Positive pressure ventilators (PPV) used by 97.7% of officers of the National Fire Service in Poland, are characterized by work that is not in line with the expectations of the firefighters. In order to improve the technical and operational features of these devices, a survey was conducted among 25,000 eligible firefighters, identifying the application of these devices, problems in use and expected development directions. A total of 682 officers voluntarily completed the survey. Based on their findings, it was determined that ventilators are most often used to smoke out buildings after or during a fire. Mentioned problems when using these devices were mainly noise (78.2%), exhaust emissions (68.5%), and impediments to mobility through the device's relatively heavy weight (40.2%). Other inconveniences were mentioned by less than 20% of firefighters. Polish firefighters expect the development of these devices mainly in terms of the above-mentioned features (noise reduction (81.7%) and reduction of the weight and size of the ventilators (about 50%)). Other expectations relate to the improvement of smoke removal in buildings: increasing the efficiency of smoke removal (46.4%) and efficiency regarding the rate of smoke removal in a building by increasing the size of the incoming airflow from the building's surroundings (33.2%). About 15% of firefighters expect changes in the operation of the ventilator itself, that is, an increase in the effective operating time (electric ventilators) and an increase in the device's uptime. The aim of the article is to identify the issues encountered during the operation and to indicate the expected direction of development for PPV by users. This information can be used by engineers to initiate new development work on these devices. [ABSTRACT FROM AUTHOR]

We used large-eddy simulation (LES) to numerically simulate two differently driven indoor airflows occurring in a multizone environment. In the first case, air flowed from one zone to another through a small hole driven by the total pressure difference. In the second case, unbalanced airflows arose from the buoyancy effect, which was generated by a heat source present in a specific location. To validate the LES prediction for the indoor flow analysis, we compared our simulation results with the chamber facility experimental results and other simulation results. Based on this validation, we confirmed that the LES reliably simulates indoor airflow. In addition, we discussed the flow characteristics and investigated the feasibility of modeling the flow rate through openings using an orifice formula. [ABSTRACT FROM AUTHOR]

Purpose: Upper respiratory tract complaints are common in the general population. A safe, non-pharmacologic treatment would be an attractive option for many patients either as an alternative to existing therapies, or as a complementary therapy. This study assessed the acceptability, safety and possible efficacy of a nasal airflow oscillation device in a group of people suffering chronic nasal congestion. Methods: Subjects with a known history of nasal congestion, but without fixed anatomical obstruction, participated in a prospective clinical study. Efficacy was assessed using peak nasal inspiratory flow (NPIF) and a 10-point visual analogue scale (VAS) administered before and after the oscillation device had been worn for twenty minutes. Results: Twenty-one subjects (mean age 37 years; 43% female) were enrolled in the study. After treatment with the small nasal airflow oscillation device for twenty minutes, average NPIF increased significantly from 84.8 L/minute to 99.0 L/minute (p < 0.05). There was a corresponding significant reduction in the VAS score for nasal congestion (p < 0.05). Similar significant improvements were also seen for the immediate sensation of nasal drainage, sinonasal pressure and overall sinonasal symptoms (p < 0.05). There was no change in the sense of smell (p = 0.37). Subjects rated ease of use highly; average = 9.1 (Range 7–10). Conclusion: Treatment of nasal congestion with the nasal airflow oscillation device was found to result in significant improvement in NPIF after twenty minutes of use. Initial patient-reported outcomes improved significantly, and the treatment was safe and highly acceptable. Trial registration: Public clinical trial registration: Universal Trial Number (U1111-1259-0704). Australian New Zealand clinical trials registration: ACTRN12623001307695. [ABSTRACT FROM AUTHOR]

Building envelope features (BEFs) have attracted more and more attention as they have a significant impact on flow structure and pollutant dispersion within street canyons. This paper conducted CFD numerical models validated by wind-tunnel experiments, to explore the effects of the BEFs on characteristics of the airflow and pollutant distribution inside a symmetric street canyon under perpendicular incoming flow. Three different BEFs (balconies, overhangs, and wing walls) and their locations and continuity/discontinuity structures were considered. For each canyon with various BEFs, the air exchange rate (ACH), airflow patterns, and pollutant distributions were evaluated and compared in detail. The results show that compared to the regular canyon, the BEFs will reduce the ACH of the canyon, but increase the disturbances (the proportion of ACH′) inside the canyon. The BEFs on the leeward wall have the least influence on the in-canyon airflow and pollutant distributions, followed by that on the windward wall. Then when the BEFs are on both walls, the ventilation capacity of the canyon is weakened greatly, and the pollutant concentration in the ground center is increased significantly, especially near the windward side. Moreover, the discontinuity BEFs will weaken the effect of the continuity BEFs on the in-canyon flow and dispersion, specifically, the discontinuity BEFs reduced the region of high pollutant concentration distributions. These findings can help optimize the BEFs design to enhance ventilation and mitigate traffic pollution. [ABSTRACT FROM AUTHOR]

Heat treatment is a common manufacturing process in the automotive industry used to produce high-performance metal components such as aluminum cylinder heads and steel gear sets. While a heat treatment schedule incorporating a quenching cycle, either through high-velocity air flow or immersion in liquids, can yield parts with durable mechanical properties, an unintended consequence of the intense quenching process is the introduction of thermal residual stress. This stress often is identified as a leading cause for quality issues related to high-cycle fatigue in aluminum engine components or geometric distortion in steel gear sets. Since thermal residual stress is caused by uneven cooling of the materials within the parts, an effective strategy for controlling thermal residual stress would involve directly managing the quenching processes. By reducing the temperature gradient inside the parts during quenching, the quality issues can be improved. Prior to the advent of computer simulation technology, the choice of quench media and the design of quenching recipes were often based on intuitive engineering judgment at best and trial-and-error iterative methods at worst. With the advancements in computational fluid dynamics (CFD) methodology, the quenching process can now be modeled through computer simulations for accurate calculation of temperature profiles and cooling histories of quenched parts. While CFD methods have the potential to manage quenching processes and mitigate thermal residual stress, it is important to note that CFD methods are not a one-size-fits-all solution for all quenching problems. Different quenching processes require different simulation strategies. Furthermore, CFD methods still require calibration and validation before they can be effectively utilized as virtual engineering tools, replacing traditional physical tryouts and experimental methods. The objective of this paper is to develop quenching simulation methodologies that can accommodate various heat treatment requirements and be used to optimize quenching processes, thereby managing quality concerns associated with thermal residual stress. While this research focuses only on two common quenching methods in engine component manufacturing, namely air quenching and water quenching for aluminum components, the principles and methodologies can be extended to other quenching methods based on convective motion of quenching media. Additionally, this research includes the parameterization and calibration of conjugate heat transfer models at the fluid-metal interface, which form the core of CFD simulation technologies. [ABSTRACT FROM AUTHOR]

In experiments in a wind tunnel, oscillations of three prisms with a rectangular cross section are studied. The prisms are located perpendicular to the velocity vector of the incoming flow and are limited from the ends by end plates that prevent air flow. The elastic suspension allows body oscillation with six degrees of freedom. It turned out that under the action of the air flow, two modes of oscillation of prism realized: translational oscillations in the direction perpendicular to the generatrix of prismatic bodies and the flow velocity, and rotational oscillations around an axis that is parallel to the generatrix, passes through the center of the prism and is perpendicular to the velocity of the incoming air flow. The tension of the two springs included in the elastic suspension is measured by the strain gauge method during the oscillation. The calibration experiment makes it possible to link the amplitudes of spring tension oscillations and phase shift with the amplitudes of rotational and translational oscillations of prisms. It turned out that a prism with a height-to-width ratio of 0.22 in the flow is subject to rotational oscillations. An increase in the ratio of height to width to 0.36 leads to a decrease in the amplitude of rotational oscillations and the appearance of translational ones. The ranges of existence of rotational and translational oscillations overlap. A further increase in the ratio of height to width to 0.43 is accompanied by intensive translational galloping. [ABSTRACT FROM AUTHOR]

The existing grape drying technology and equipment often have problems such as poor hygiene conditions, high drying costs, and large drug residues. Therefore, the market urgently needs grape drying equipment with low energy consumption, high efficiency, and a green-clean processing process. To solve the above problems, a piece of integrated drying equipment combining the two technologies of air impingement blanching and air impingement drying for multi-layer grape material drying is designed. The dried product quality is directly affected by the airflow field distribution. Therefore, obtaining good airflow distribution and airflow velocity uniformity in the drying chamber via parametric studies is essential to ensure uniform drying of products. Since parametric and optimization investigations by physical experiments are usually expensive and time-consuming, computational fluid dynamics (CFD) being a flexible and less expensive tool can be employed to perform such studies. In the current work, the airflow velocity distribution and uniformity of the drying material room are analyzed by Ansys Fluent software. The airflow velocity non-uniformity coefficient is used to evaluate airflow uniformity. Results show that the original design has poor uniformity and needs to be optimized. The influence of air inlet chamber deflection device and material truck airflow baffles on the flow field of the material drying room is investigated to improve the uniformity of airflow distribution. Considering drying efficiency and uniformity, drying material room structure with the addition of deflection device design with the structural parameters of L = 50 mm and θ = 76°, airflow baffle design with the structural parameters of h = 0 mm, θ2 = 20° is chosen as the final optimized design. After optimization, the velocity of airflow between material layers has improved overall, and the maximum difference of average airflow velocity between material layers has been reduced from 0.73 m/s to 0.69 m/s, improving the drying uniformity of dried materials. In comparison to other drying equipment, the current integrated drying equipment combing air impingement blanching and drying has the advantages of being efficient and energy-saving, suitable for large-scale drying of grapes with better drying quality. The current results could guide the drying equipment design for grapes and develop the grape drying industry with high-dried quality. [ABSTRACT FROM AUTHOR]

Drying harvested grain crops prior to storage is a crucial task in the prevailing climatic conditions of Europe. Drying is an extremely energy-intensive process. Its inappropriate application leads to environmental pollution, quality deterioration, and ultimately significant financial losses. Various methods are available for conducting drying operations, with the mixed flow dryer being one of the most employed approach. The mixed flow dryer utilizes air blower systems to redirect the flow of the granulate. Previous research has indicated that uneven distribution of grain flow around the air blower lamellae can cause drying irregularities. By leveraging insights from a long-established classical mechanical problem (the Brachistochrone problem) and harnessing the explicit dynamical modelling capabilities offered by contemporary computing technology (Discrete element method), we have successfully devised an optimized lamella geometry that minimizes the non-uniformity of particle flow. [ABSTRACT FROM AUTHOR]

An approach to estimating the dry deposition velocity of aerosol particles on the surfaces of Arctic regions, where snow-covered surfaces, open-water surfaces, tundra, and coniferous forest predominate, is proposed and numerically investigated. Optimal modeling conditions are proposed, taking into account the characteristic sizes and densities of aerosol particles involved in transport in the planetary boundary layer and the interaction of air flows with the surface through the parameter u*, calculated using the WRF-ARW model. The proposed approach is compared with other known models and experimental data. The dependence of the dry deposition velocity obtained by this approach on the diameter, density of aerosol particles, and dynamic velocity u* for the surfaces in the Far North is estimated. [ABSTRACT FROM AUTHOR]

Ground-based measurements of the vertical atmospheric electric field of the Earth sometimes show bay-like anomalies that precede some earthquakes. In some cases, these anomalies have even been accompanied by a change in the sign of the field under fair weather conditions. Possible causes of this phenomenon are typically attributed to anomalous changes in the electrical conductivity in the near-surface atmospheric layer, increased radon emission from the soil, etc. This paper proposes another mechanism of atmospheric electrical anomalies, which involves the entrainment of charged aerosols as well as light and heavy ions by air flows. Such flows can be produced due to small temperature anomalies observed before some seismic events. Theoretical analysis shows that anomalously strong electrical variations may occur even in the presence of weak air flows provided that they persist for a long time and a peculiar structure of the velocity field, which presumes vertical air circulation and particle exchange between different atmospheric layers. For this type of flows, an analytic solution is derived and spatial distributions of atmospheric electric perturbations are obtained. The results of calculations and estimates confirm that the proposed mechanism can explain the observation data. [ABSTRACT FROM AUTHOR]

Wind speed is an important variable in the assessment of thermal comfort. Different types of meteorological devices provide different accuracy of air velocity (va) measurements, which under limited air flow conditions, may result in a discrepancy in actual thermal stress level. Simultaneous measurements on warm summer days, performed with a cup anemometer and hot-wire probe, prove that too high starting threshold of the first of these sensors can lead to a discrepancy of actual wind speed, and as a consequence can distort MRT (estimated with globe thermometers) and PET values on average up to 10 °C and 1 °C, respectively. [ABSTRACT FROM AUTHOR]

Exposure to UV-A light was paired with low RH air flow for the dehydration of both mango and apple. Control samples of each were dehydrated with the low RH air and no UV-A light in order to determine the significance of the UV-A light in the dehydration process. The control mango contained approximately 85% more moisture wet basis than the UV-A light–dehydrated samples which resulted in approximately 91.4 ± 4.5% of the original mass of water being removed. The control apple contained approximately 55% more moisture wet basis than the UV-A light–dehydrated samples which resulted in approximately 96.0 ± 0.1% of the original mass of water being removed. The preservation of the physical and chemical integrity of the UV-A light–dehydrated samples was confirmed using electron microscopy and infrared spectroscopy analyses even after prolonged storage at a wide range of RH levels (11.3–86%). The thermal properties associated with certain physical properties of the samples were analyzed using a differential scanning calorimeter, confirming the preservation of the physical integrity of the samples. Despite not having any pretreatments for enzyme inactivation, the UV-A light–dehydrated mango and apple samples preserved much of their original color as compared to the control samples. [ABSTRACT FROM AUTHOR]

Rapid development of the anomalous enhancement of separated turbulent Re = 6000 air flow and heat transfer in an in-line single-row package of 31 inclined grooves, 0.2 in dimensionless depth, in a singled-out longitudinal region of the wall of a narrow channel is studied. It is due to the interference of vortex wakes behind the grooves and the acceleration in the channel flow core with the formation of a zone of ultrahigh longitudinal velocity. The wave-shaped parameter characteristics are stabilized in the region of approximately 15th groove, whereupon the oscillation amplitudes are moderately reduced. The return flows in the grooves are enhanced with distance from the entry section, the minimum negative friction diminishing from −2 to −4. The total relative heat removal from the structured region increases at q = const by a factor of approximately 2.75 and by the factor of two at T = const with increase in the relative hydraulic losses by the factor of 1.7, as compared with the case of a plane–parallel channel. The relative heat removal from the surface bounded by the contour of the 20th inclined groove amounts to 3.7 (q = const) with increase in the hydraulic losses by the factor of 2.2. An increase in the local maximum of the longitudinal velocity up to a factor of 1.5, as compared with the mean-mass velocity, can be observable. [ABSTRACT FROM AUTHOR]

In order to study the problems of unreasonable airflow distribution and serious dust pollution in a heading surface, an experimental platform for forced ventilation and dust removal was built based on the similar principles. Through the similar experiment and numerical simulation, the distribution of airflow field in the roadway and the spatial and temporal evolution of dust pollution under the conditions of forced ventilation were determined. The airflow field in the roadway can be divided into three zones: jet zone, vortex zone and reflux zone. The dust concentration gradually decreases from the head to the rear of the roadway. Under the forced ventilation conditions, there is a unilateral accumulation of dust, with higher dust concentrations away from the ducts. The position of the equipment has an interception effect on the dust. The maximum error between the test value and the simulation result is 12.9%, which verifies the accuracy of the experimental results. The research results can provide theoretical guidance for the application of dust removal technology in coal mine. [ABSTRACT FROM AUTHOR]