Strong Airflow Research Articles

Walking-induced particle resuspension in a commercial airliner cabin under different ventilation systems

The potential health risk posed by particle resuspension in the air of an airliner cabin is a concern for passengers. This study employed computational fluid dynamics (CFD) to analyze particle dispersion patterns under different ventilation systems, such as mixing ventilation (MV), underfloor air distribution (UFAD), and aisle displacement ventilation (ADV), within a twin-aisle cabin environment. To ensure the accuracy of the CFD model, the study validated the simulated air velocity distribution against experimental airflow patterns from a small-scale water model reported in existing literature. Additionally, the research included direct measurements of particle resuspension within the breathing zone of a full-scale, twin-aisle cabin mockup, which featured five rows of seats. These measurements were taken in response to the disturbance caused by a volunteer walking over an aviation carpet in the aisle. While the CFD simulation results generally aligned with the experimental data, some discrepancies were noted. Pinpointing the exact causes of these discrepancies proved challenging due to the numerous uncertainties and approximations inherent in the study. Nevertheless, the investigation revealed that the air in the upper region near the moving body was pushed forward, creating a strong airflow that enveloped the body. This dynamic resulted in the formation of a wake that lifted particles from the floor level to the upper cabin area. The study observed that particle concentration within the breathing zone increased in the direction of movement. The airflow patterns produced by the three ventilation systems were different. Despite the cabin's symmetrical design, some particles can still transfer from one side to the other, especially under the MV system. The peak particle concentration in the breathing zone was recorded at 20 s, after which it decreased to negligible levels by 120 s. Among the ventilation systems analyzed, the MV system exhibited the highest peak particle concentration, while the UFAD system showed the lowest peak. However, the UFAD system also presented the possibility of very high particle concentrations at certain seats.

Study on multiple influence mechanism of airflow-dust-gas coupling diffusion under large vortex flow technology

In response to the serious dust pollution and excessive gas concentration in fully mechanized excavation face, a multi-phase coupling diffusion model of airflow-dust-gas was established, and the influence of pressure pumping ratio and air volume on dust and gas diffusion was studied. The results showed that the dust of the traditional ventilation mode was diffused to the whole roadway, and the high-concentration gas accumulated obviously. However, after adopting the new ventilation mode of large vortex flow, a quantity of dust was controlled in the eddy field, and high-concentration gas was dissipated by strong airflow, so there was no gas accumulation. As the pressure pumping ratio decreases, the extraction effect increases, the eddy current intensity also increases, and the control effect on dust is enhanced. The pressure pumping ratio with the best dust control effect is 0.6, and there is no dust pollution and no gas accumulation in the driver's location. The fixed pressure pumping ratio is 0.6, and the diffusion of dust and gas is not significantly affected by an increase in air volume, but high-speed airflow can dilute and reduce the concentration of dust and gas. When Qb = 600.0 mg/m³, the high-speed airflow can dilute the dust concentration, accelerate the dispersion of high-concentration gas, keep the gas below the safe level, and have a good dust control effect. The increase of air volume will further reduce the dust and gas concentration. This study provides a theoretical basis for the promotion and utilization of new ventilation method on-site.

Facile synthesis of a novel organic salt containing DOPO and pyrimidine as a reactive additive for high‐efficiency flame retarding epoxy resin

AbstractA novel organic salt containing DOPO and pyrimidine (AD) was successfully synthesized through a simple acid–base neutralization reaction. The salt was used as a reactive flame retardant for epoxy resin. Non‐isothermal DSC tests disclosed that the epoxy resin displayed a lower temperature of onset curing and exothermic peak in the presence of AD. By using only 3 wt% AD, the epoxy resin achieved a UL‐94 V‐0 rating and a limited oxygen index value of 27.4%, revealing the high flame‐retardant efficiency of AD. AD inhibited the release of heat and smoke. The analysis of the flame‐retardant mode of action indicated that AD was able to impede combustion not only by the dilution and quenching effects in the gas phase but also by the charring effect in the condensed phase. During UL‐94 testing, 3 wt% AD gave the epoxy resin good flame retardancy due to the charring and blowing‐out effects formed by adding AD. The blowing‐out effect was that the release of strong airflows suppressed or even blew out the flame based on the dilution and quenching effects of phosphorous‐containing radicals and numerous non‐combustible gases produced by the degradation of AD and epoxy resin matrix. Additionally, the incorporation of AD slightly increased the glass transition temperature and the tensile and flexural strengths of the epoxy resin. This study provided a meaningful attempt to improve the flame retardance of epoxy resin by introducing a reactive pyrimidine‐organophosphonic acid salt.

Comparing the mechanisms of two types of summer extreme precipitation in Beijing-Tianjin-Hebei region, China: Insights from circulation patterns and moisture transports

Beijing-Tianjin-Hebei (BTH) is undergoing huge risks from severe precipitation extremes, but their climate features and underlying mechanisms are not fully understood and warrant in-depth investigations. Here, the summer extreme precipitation events in BTH are objectively divided into two types according to the spatial distribution i.e., Northeast precipitation (NEP) and Southwest precipitation (SWP) and their underlying mechanisms are revealed and compared from perspectives of circulation patterns and moisture transports. In the case of Type NEP, the anomalous deep low-pressure (high-pressure) systems respectively cover over the west (east) of BTH, which jointly induce strong anomalous southwesterly and southerly airflows converging over BTH. The converging airflows strengthen water vapor transports from the western and southern boundaries of BTH and result in a strong convection over northeastern BTH, thereby triggering Type NEP precipitation. Compared with Type NEP, the circulation pattern of Type SWP is characterized by an anomalous deep (shallow) high-pressure (low-pressure) system over northeast (southwest) of BTH, respectively. The circulation patterns could induce strong anomalous southerly and easterly airflows converging over BTH and thus strengthen water vapor transports from the southern and eastern boundaries of BTH, resulting in a strong convection over southwestern BTH. Over the long-term period, the summer extreme precipitation days with multiple return periods extracted by the Generalized extreme value distribution theory show significantly increasing trends in Beijing-Tianjin and surrounding areas, particularly in urban regions, indicating that summer extreme precipitation events are becoming more frequent. These findings provide theoretical basis for summer extreme precipitation forecasting and scientific insight for taking effective measures to mitigate the corresponding disasters in BTH.

Enhanced green remediation and refinement disposal of electrolytic manganese residue using air-jet milling and horizontal-shaking leaching

The reclamation and reuse of electrolytic manganese residue (EMR) as a bulk hazard solid waste are limited by its residual ammonia nitrogen (NH4+-N) and manganese (Mn2+). This work adopts a co-processing strategy comprising air-jet milling (AJM) and horizontal-shaking leaching (HSL) for refining and leaching disposal of NH4+-N and Mn2+ in EMR. Results indicate that the co-use of AJM and HSL could significantly enhance the leaching of NH4+-N and Mn2+ in EMR. Under optimal milling conditions (50 Hz frequency, 10 min milling time, 12 h oscillation time, 400 rpm rate, 30 ℃ temperature, and solid-to-liquid ratio of 1:30), NH4+-N and Mn2+ leaching efficiencies were optimized to 96.73% and 97.35%, respectively, while the fineness of EMR was refined to 1.78 µm. The leaching efficiencies of NH4+-N and Mn2+ were 58.83% and 46.96% higher than those attained without AJM processing. The AJM used strong airflow to give necessary kinetic energy to EMR particles, which then collided and sifted to become refined particles. The AJM disposal converted kinetic energy into heat energy upon particle collisions, causing EMR phase transformation, and particularly hydrated sulfate dehydration. The work provides a fire-new and high-efficiency method for significantly and simply leaching NH4+-N and Mn2+ from EMR.

Radar Characteristics and Causal Analysis of Two Consecutive Tornado Events Associated with Heavy Precipitation during the Mei-Yu Season

This paper comprehensively analyzed two consecutive tornado events associated with heavy precipitation during the Mei-yu season (a period of continuous rainy weather that occurs in the middle and lower reaches of the Yangtze River in China from mid-June to mid-July each year) and detailed the formation and development process of the tornadoes using Doppler weather radar, wind profiler radar, ERA5 reanalysis data, ground automatic station data and other multi-source data. The results showed that: (1) Small-scale vortices were triggered and developed during the eastward movement of the low vortex, forming two tornadoes successively on the eastern section of the Mei-yu front. (2) The presence of a gap on the front side of the reflectivity factor profile indicated that strong incoming airflow entered the updraft. Mesocyclones were detected with decreasing heights and increasing shear strengths. The bottom height of the tornado vortex signature (TVS) dropped to 0.7 km, and the shear value increased to 55.4 × 10−3 s−1. Tornado debris signatures (TDSs) could be seen with a low cross-correlation coefficient (CC) value area of 0.85–0.9 in the mesocyclone. The difference between the lowest-level difference velocity (LLDV) and the maximum difference velocity (MXDV) reached the largest value when a tornado occurred. (3) The continuously enhanced low-level jet propagated downward to form a super-low-level jet, and the strong wind direction and wind speed convergence in the boundary layer created a warm, moist and unstable atmosphere in Suzhou. With the entrainment of dry air, the northwest dry jet and the southeast moist jet stimulated the formation of a miniature supercell. (4) The low-level vertical wind shear of 0–1 km increased significantly upon tornado occurrence, which was more conducive to the formation and intensification of horizontal vorticity tubes. Encountering updrafts and downdrafts, the vorticity tubes might have been stretched and intensified. The first lightning jumps appeared 15 min and 66 min earlier than the Kunshan Bacheng tornado and the Taicang Liuhe tornado. The Liuhe tornado occurred during the stage when the lightning frequency reached its peak and then fell back.

Flame and burning dynamics of pool fire inside semi-confined compartment under external cross wind

In this paper, experimental and theoretical studies of the flame shape and burning rate of pool fire inside a semi-confined compartment (with one sidewall and ceiling open) under the cross wind were investigated. The effects of fuel pool size and cross wind velocity on the flame morphological parameters and burning rate were obtained. Three typical bending behavior of the tilted flame was observed during the experiments. The dimensionless burning rate m˙″* decreased slightly when Frw<1, and increased linearly with Frw when Frw≥1. An air gap (δair) between the flame and sidewall was observed because of the restriction of the sidewall and blow-off by strong airflow recirculation. Theoretical analysis of wind-blown pool fire inside the semi-confined compartment was conducted based on the asymmetrical air entrainment and the buoyancy length scale. A dimensionless parameter (sm˙fρ∞uwlb2) considering the burning rate and cross wind velocity was proposed to predict the flame height, flame tilted angle and air gap thickness. The flame morphological characteristic parameters and the thickness of the air gap were correlated linearly well with the dimensionless parameter in exponent expression.

Numerical study of indoor flow field and ventilation performance of the power room of a diesel locomotive under crosswind

Power room is the core part of the railway internal combustion locomotives, houses many high-power equipment within a limited space. The ventilation performance of a power room are the key factors that ensure the efficient operation of locomotives. Numerical simulations were conducted to study the indoor and outdoor flow fields of the power room, with focus primarily on the indoor flow field of the locomotive. The effects of locomotive and crosswind speeds on the ventilation performance and indoor flow field of a power room were studied. Furthermore, the effects of fan performance on the power room ventilation were compared and analyzed. The numerical methods used were verified using experimental data. Results showed that as locomotive speed increased, the power room ventilation performance decreased, while the airflow rate of certain power room air intakes increased, with an increase in locomotive speed. Crosswinds significantly increased the power room ventilation quantity, especially when the intakes faced the crosswind. When the crosswind speed surpassed a certain threshold, the intakes on the leeward side of the power room entered an air-leakage state. The indoor flow field distribution of the power room was unaffected by the fan performance. Though the effect of fan performance on the amount of airflow entering the power room varied, the fan performance positively correlated with the overall ventilation performance of the power room. Considering the strong airflow separation caused by the back-step corner of the driver cab, attention should be paid to the placement and intake position of the power room in the design stage.

Analysis of Interannual Anomalies and Causes of Compound Extreme Wind and Precipitation Events in Spring over the Jiangsu–Anhui Region

By using the daily average wind speed and precipitation data of 125 stations in Jiangsu and Anhui Provinces of China from 1961 to 2020 and the monthly NCEP/NCAR reanalysis data, the interannual variation characteristics and its possible reasons of spring compound extreme wind and precipitation events in the Jiangsu–Anhui region were discussed. Results show that the spring compound extreme wind and precipitation events generally present a lesser distribution in the south and more in the north. The events occurring in south (north) of 32° N are basically less than (above) three days, and in some areas of northern Jiangsu, it can reach more than four days. On a regional average, the spring compound extreme wind and precipitation events have presented a significant downward trend in the past 60 years. In addition, there was an interdecadal mutation from more to less in the early 1990s, with the most significant decline in the coastal areas of northern Jiangsu. Further analysis reveals that the synthetic height anomaly field at 500 hPa corresponding to the frequent occurrence of the spring compound extreme wind and precipitation events is positive in the northern region of 45° N, while it is negative in the southern region of 45° N, which enhances the high pressure in high latitudes, increases the meridional gradient of circulation, and promotes the activity of high-latitude short-wave trough ridges and cold air. Meanwhile, a strong southwest airflow exists in the corresponding middle and low latitudes at 850 hPa, so the water vapor from the Bay of Bengal can be continuously transported to the Jiangsu–Anhui region. Overall, the abundant water vapor transportation and the convergence of southward cold air in high latitudes are conducive to the occurrence of extreme wind and precipitation events.

Dynamic Response of Outer Windshield Structure in Different Schemes under Aerodynamic Load

With the increase in high-speed train (HST) operation speed, the light-weight design of the train body and component structure is pursued to reduce energy consumption during operation, but this seriously deteriorates the aerodynamic performance of the light-weight structure outside the train body under the effect of strong unsteady airflow, and the more obvious case is the frequently occurring problem of vibration, large deformation, and damage to the rubber exterior windshield at the connection position of HST carriages. We investigate the fluid–structure coupling mechanism of the interaction between the rubber external windshield and aerodynamic force, and compare the dynamic characteristics of windshield structure under different design parameters. A numerical simulation of three rubber outer windshield structure parameters (sidewall distance of U-shaped capsule, sidewall thickness, sidewall inclination angle) is carried out using FSI simulation of the two-way coupling method. The aerodynamic load, airflow dynamics around the windshield, and the nonlinear vibration and deformation form of the windshield is analyzed in detail. The results show that the aerodynamic response of the HST rubber external windshield analyzed by the FSI method is in good agreement with the full-scale test results. Additionally, the stiffness of the windshield can be improved by increasing the thickness of the windshield sidewall. When the distance between the sidewall of the windshield is increased, an insufficient thickness at the top of the arc causes a large local deformation at the top of the arc of the windshield. The method established and relevant research results can provide good support for the aerodynamic stability evaluation of HST windshields.

Meteorological Characteristics, Influence Analysis and Prediction of PM2.5 Concentration in Taiyuan City

Based on the pollutant concentration data of Taiyuan City from 2016 to 2020 and the surface meteorological data of the national benchmark meteorological observation station in the same period, the variation characteristics of PM2.5 concentration in Taiyuan City and the effects of meteorological conditions such as humidity, precipitation, wind, and mixing layer thickness on PM2.5 concentration were analyzed. At the same time, the causes of pollutant concentration changes were discussed, and the PM2.5 concentration prediction model based on the LSTM neural network was established. The results showed that the number of days of heavy pollution in Taiyuan City from 2016 to 2020 was the highest in winter, of which the maximum number of days in 2017 was 28 days. The PM2.5 concentration was generally high in autumn and winter and low in spring and summer. The PM2.5 concentration on weekends was higher than that on weekdays. The daily variation in PM2.5 concentration roughly presented a bimodal distribution, which appeared around 09:00 and 23:00 to 01:00 the following day. Except for relative humidity and winter temperature, other air pressure, wind speed, and PM concentration showed negative correlations in the four seasons. The pollution sources affecting the increase in PM2.5 concentration in Taiyuan City were mainly located in the NE-ENE-E direction, and the pollution in the northwest was not relatively apparent. In flood season, when the precipitation reached the level of moderate rain (rainfall ≥ 10 mm), it had an obvious effect on the reduction of PM2.5 concentration. The increase in atmospheric mixing layer height was very beneficial to the diffusion and dilution of PM2.5 in the vertical direction. The strong northwest air flow in winter, low relative humidity, high pressure control on the ground, and high height of the mixing layer belonged to the cluster most conducive to the reduction in PM2.5 concentration. Using the LSTM model for modeling, the R2 of PM2.5 concentration prediction was as high as 0.95, which was significantly better than that of the traditional tree model and linear regression model (R2<0.60). The residual of the prediction results was close to the normal distribution, of which the absolute error of 84.2% prediction results was less than 20 μg·m-3, and the MAE, MAPE, and RMSE of the model were 38.17, 17.19%, and 20.6, respectively.

Large-scale moisture transport and local-scale convection patterns associated with warm-sector heavy rainfall over South China

Warm-sector heavy rainfall (WSHR) frequently occurs in South China, causing severe floods and posing serious threats to human health and societal systems there. However, its moisture sources, transport pathways, and triggering mechanisms still warrant in-depth investigations. Here we identify three different clusters of moisture sources and transport pathways of WSHR in South China during 1982–2015 and reveal their associated atmospheric circulations and local-scale convection patterns. In the case of cluster 1, a strong anomalous high-pressure system and an anomalous low-pressure system jointly induce strong southwesterly air-flows, and a local convergent flow and ascending motions appear over the west of South China, thereby providing sufficient water vapor from the Indian Ocean and favorable dynamical conditions for triggering WSHR events in the west of South China. In contrast, the trajectories of cluster 2 are characterized by strong easterly air-flows that supply a large amount of water vapor from the Northwest Pacific and induce a strong convection, favoring the WSHR occurrences in the eastern coastal area of South China. In the case of cluster 3, a high-pressure anomaly and a shallow low-pressure system respectively cover the southeast and northwest portions of South China. This circulation pattern causes a strong anomalous southerly wind and induces an anomalous convergent flow over entire South China, thereby transporting sufficient water vapor from the South China Sea and triggering WSHR events over South China. Differing from WSHR, the moisture of frontal heavy rainfall events over South China is not only contributed by the three dominant ocean-originating moisture transport paths but also by the continent-originating paths. The findings reported here highlight that the atmospheric trajectories and synoptic systems jointly modulate the spatial variation of heavy rainfall events in South China by dominating large-scale transport pathways of water vapor and local-scale convection patterns.

Extreme Rainfall and Flood Risk Prediction over the East Coast of South Africa

Extreme rainfall associated with mid-tropospheric cut-off low (COL) pressure systems affected the entire east coast of South Africa during April 2022, leading to flooding and destruction of homes, electricity power lines, and road infrastructure, and leaving 448 people confirmed dead. Therefore, this study investigated the evolution of the two COLs and their impacts, including the occurrence of extreme rainfall and cold weather over the southeast coast of the country. We analysed observed and reanalysis meteorological data and mapped areas at risk to impacts of flood hazards on the east coast of South Africa. Extreme rainfall (&gt;500 mm) accumulated over 16 days was observed along the east coast, with the amount of rainfall progressively decreasing inland. We found that the rainfall associated with the first COL was significantly enhanced by the interactions between a strong low-level onshore airflow across the Agulhas Current and the coastal escarpment, resulting in deep convection and lifting. An unusual surface cyclone with tropical characteristics developed over the subtropical southwest Indian Ocean, driving onshore southeasterly winds which enhanced low-level convergence. Moreover, the flood risk results revealed that, amongst others, land cover/use (52.8%), elevation (16.8%) and lithology (15.5%) were the most important flood predictor variables in this study. Much of the study area was found to have very low (28.33%), low (31.82%), and moderate (21.66%) flood risk, whilst the high- and very-high-risk areas accounted for only 17.5% of the total land area. Nonetheless, the derived flood risk map achieved an acceptable level of accuracy of about 89.9% (Area Under Curve = 0.899). The findings of this study contribute to understanding extreme rainfall events and the vulnerability of settlements on South Africa’s east coast to flood risk, which can be used towards natural disaster risk reduction.

Particle exposure risk to a lavatory user after flushing a squat toilet

Squat toilets are widely used in developing countries due to local customs and low costs. The flushing of a squat toilet can entrain strong airflow and produce aerosols. This investigation constructed a lavatory mock-up with a squat toilet. The flushing-induced airflow was both visualized and quantitatively measured by particle image velocimetry. The maximum height of the impacted airflow was identified by an ultrasonic anemometer. For inference of the particle emission rate, the toilet bowl was covered by an enclosed box for particle concentration measurement. The risks from skin contact of the deposited particles on the flushing button and the door handle and the possible inhalation of the released aerosols were evaluated. The results revealed that flushing a squat toilet can drive toilet plume to rise up to 0.9 m above the toilet bowl. A single flushing process can produce 0.29 million particles with diameters greater than 0.3 μm, among which 90% of the particles are submicron-sized. The flushing may cause particles to deposit on the flushing button and lavatory door handle as well as inhalation exposure even remaining in the lavatory for half a minute after flushing, especially for those lavatory users whose respiratory zones are below 1.0 m.

Drift characteristics and the multi-field coupling stress mechanism of the pantograph-catenary arc under low air pressure

The fault caused by a pantograph-catenary arc is the main factor that threatens the stability of high-speed railway energy transmission. Pantograph-catenary arc vertical drift is more severe than the case under normal pressure, as it is easy to develop the rigid busbar, which may lead to the flashover occurring around the support insulators. We establish a pantograph-catenary arc experiment and diagnosis platform to simulate low pressure and strong airflow environment. Meanwhile, the variation law of arc drift height with time under different air pressures and airflow velocities is analyzed. Moreover, arc drift characteristics and influencing factors are explored. The physical process of the arc column drifting to the rigid busbar with the jumping mechanism of the arc root on the rigid busbar is summarized. In order to further explore the mechanism of the above physical process, a multi-field stress coupling model is built, as the multi-stress variation law of arc is quantitatively evaluated. The dynamic action mechanism of multi-field stress on arc drifting characteristics is explored, as the physical mechanism of arc drifting under low pressure is theoretically explained. The research results provide theoretical support for arc suppression in high-altitude areas.

Effects of void deck on the airflow and pollutant dispersion in 3D street canyons.

In general, urban canyons are the areas most clearly affected by traffic pollutants since the ability of the canyon to self-ventilate is inhibited due to blockage of buildings or other urban structures. However, previous studies have aimed to improve the pedestrian-level wind speed with void deck in single buildings or short canyons. This study investigated the effects of void deck height and location, and the building height on the airflow field and the traffic pollutant diffusion in a long canyon with L/H = 10, validated by wind-tunnel experiment data. The results show that the void decks have a significant effect on the airflow and pollutant distribution inside the canyon. Air exchange rates (ACH) of the canyons with the void deck are much larger than that of regular canyons, and the perturbation changes of turbulence (ACH′) decrease. For the windward void deck, purging flow rate (PFR) and normalized net escape velocity (NEV*) increase by 6.4 times compared to the regular canyon, and for the leeward void deck, increase by 13 times. In particular, when the void decks are at both buildings, they are increased by 38.3 times. Also, for the canyons with the void deck, traffic pollutants are removed out of the canyon by the strong airflow through the void deck. Therefore, unlike the regular canyons, as the void deck and the building height increases, the strength of the airflow through the void deck becomes stronger, and as a result, the mean pollutant concentration is significantly reduced at both walls and the pedestrian respiration level. The mean pollutant concentration on the wall of the building with the void deck and on the pedestrian respiration plane close to it is near zero. These findings can help ease traffic pollution inside the street canyons composed of high-rise buildings, especially in tropical cities.

Effect of surface air cooling on the high frequent cyclic ablation of C/C–SiC–ZrB2–ZrC composite under ms-scale single loading

Influence of surface air cooling on the high frequent cyclic ablation of layer-structural C/C–SiC–ZrB2–ZrC composite was mainly studied. Tests were performed by alternant plasma and surface cooling airflow for 200 cycles under ms-scale single loading. The C/C–SiC–ZrB2–ZrC composite displayed good ablation resistance. And the ablation rates decreased firstly and then rose up with increasing of the airflow rate from 0 to 4 m3/h, whereas the highest surface temperature presented an inverse relationship. The lowest ablation rates were 0.12 μm/s and 0.038 mg/s under surface airflow of 2 m3/h. Morphologies and phases of the ablated surface indicated that the low-speed airflow was helpful to the spread out and accumulation of the ablation products whereas the stronger airflow caused surface cracks and fragments of the composite. The intensities of the mechanical erosion under different surface air cooling dominated the high frequent cyclic ablation behavior.

CFD models as a tool to analyze the deformation behavior of grape leaves under an air-assisted sprayer

The air-assisted sprayer can effectively promote the deformation of tree leaves and improve the deposition performance of droplets in the target canopy interior with the help of strong assisted airflow. This study selected the grape leaves as the research object to clarify the deformation behavior of leaves under the assisted airflow. Firstly, a bidirectional fluid–structure interaction model was established using computational fluid dynamics (CFD) based on the measurement of leaves parameters. The model was verified by a high-speed camera, and the maximum deformation of leaves centroid and tip in CFD simulation were compared with the shooting results. The maximum relative error was 8.73%, which shows that the model can accurately simulate the deformation of the grape leaves. Secondly, a universal rotation center combination simulation was carried out by taking the airflow velocity (v), airflow angle (α), leaf inclination angle (β), and stalk leaf angle (γ) as experimental factors. The regression analysis shows that the mean absolute percentage error (MAPE) of leaves centroid and tip regression equations was 2.12% and 2.57%, and the coefficient of determination (R2) was 0.9578 and 0.9607, respectively. Further, the MAPE between the theoretical and simulated values of the change of leaf inclination angle was 2.53%, and R2 was 0.9619. The maximum relative error between the theoretical and actual values was 11.46%, indicating that the method proposed in this paper is accurate to some extent in predicting the leaf inclination angle.Finally, this paper analyzed the variation of the windward area of grape leaves and emphasized the necessity of applying appropriate assisted airflow according to the leaf growth characteristics. The research results of this paper can provide a reference for the regulation and optimization of the pneumatic system of sprayers.

Study on the discharge characteristics along the surface of insulating media in the low air pressure and strong airflow environment

In this paper, a surface discharge test was conducted on a silicone rubber insulating sheet, an epoxy resin insulating sheet, a porcelain insulating sheet, and a glass insulating sheet by using an independently constructed test platform of insulating media to study the discharge characteristics along the surface of insulating media under low air pressure and strong airflow environment. Experiments were conducted to obtain the variation in the discharge characteristics along the surface of the four kinds of insulation media with respect to airflow velocity at different air pressures. The discharge voltage characteristics and discharge morphology characteristics along the surface of the insulating media in a strong airflow environment at low air pressure are elucidated. This paper provides theoretical support for the selection of insulation materials and insulation protection design for a low air pressure and strong airflow environment.

Study on the distribution characteristics of dust with different particle sizes under forced ventilation in a heading face

Coal mines face a significant situation with regard to dust control. Numerical simulation was used in this paper to study the distribution of dust of different particle sizes in a specific case, as well as the influence of changing the supply airflow velocity on the dust distribution. The findings demonstrate that the airflow primarily migrates from the return air side to the air inlet side and the exit, with the intensity of the airflow decreasing as the distance increases. The amount of dust is high in the area with a strong airflow and low in other areas, and dust of different particle sizes is separated gradually. Increasing the supply air velocity has a greater effect on large dust particles than on small dust particles under the conditions and air speed range studied in this paper. Reasonable reduction of the supply air velocity can effectively reduce the amount of suspended dust.