Effect Of Air Flow Research Articles

Breathing on chip: Dynamic flow and stretch accelerate mucociliary maturation of airway epithelium in vitro.

Human lung function is intricately linked to blood flow and breathing cycles, but it remains unknown how these dynamic cues shape human airway epithelial biology. Here we report a state-of-the-art protocol for studying the effects of dynamic medium and airflow as well as stretch on human primary airway epithelial cell differentiation and maturation, including mucociliary clearance, using an organ-on-chip device. Perfused epithelial cell cultures displayed accelerated maturation and polarization of mucociliary clearance, and changes in specific cell-types when compared to traditional (static) culture methods. Additional application of airflow and stretch to the airway chip resulted in an increase in polarization of mucociliary clearance towards the applied flow, reduced baseline secretion of interleukin-8 and other inflammatory proteins, and reduced gene expression of matrix metalloproteinase (MMP) 9, fibronectin, and other extracellular matrix factors. These results indicate that breathing-like mechanical stimuli are important modulators of airway epithelial cell differentiation and maturation and that their fine-tuned application could generate models of specific epithelial pathologies, including mucociliary (dys)function.

Dynamic behavior of outburst two-phase flow in a coal mine T-shaped roadway: The formation of impact airflow and its disaster-causing effect

The study of the dynamic disaster mechanism of coal and gas outburst two-phase flow is crucial for improving disaster reduction and rescue ability of coal mine outburst accidents. An outburst test in a T-shaped roadway was conducted using a self-developed large-scale outburst dynamic disaster test system. We investigated the release characteristics of main energy sources in coal seam, and obtained the dynamic characteristics of outburst two-phase flow in a roadway. Additionally, we established a formation model for outburst impact flow and a model for its flow in a bifurcated structure. The results indicate that the outburst process exhibits pulse characteristics, and the rapid destruction process of coal seam and the blocking state of gas flow are the main causes of the pulse phenomenon. The outburst energy is released in stages, and the elastic potential energy is released in the vertical direction before the horizontal direction. In a straight roadway, the impact force oscillates along the roadway. With an increase in the solid–gas ratio, the two-phase flow impact force gradually increases, and the disaster range extends from the middle of the roadway to the coal seam. In the area near the coal seam, the disaster caused by the two-phase flow impact is characterized by intermittent recovery. In a bifurcated roadway, the effect of impact airflow on impact dynamic disaster is much higher than that of two-phase flow, and the impact force tends to weaken with increasing solid-gas ratio. The impact force is asymmetrically distributed; it is higher on the left of the bifurcated roadway. With an increase in the solid-gas ratio, the static pressure rapidly decreases, and the bifurcated structure accelerates the attenuation of static pressure. Moreover, secondary acceleration is observed when the shock wave moves along the T-shaped roadway, indicating that the bifurcated structure increases the shock wave velocity.

Injection parameter design to improve the high-speed gear heat dissipation: CFD simulation and regression orthogonal experiment

A heat dissipation model of high-speed helical gears based on Computational Fluid Dynamics (CFD) is proposed under injection lubrication. Gear heat dissipation is investigated by static and dynamic heat flow coupling. The oil injection lubrication test is designed to measure tooth temperature by an infrared thermal imager. The results show that owing to the gear centrifugal force, the oil splash, and the blocking effect of the high-speed airflow, the average temperature first decreases and then increases, and the temperature difference increases first and then decreases with the increase in injection angle, distance, and velocity. The average temperature and temperature difference are remarkably affected by the injection velocity and distance, respectively. The optimal injection angle, distance, and velocity predicted by the regression orthogonal method are 9.212°, 54.514 mm and 35.561 m/s, respectively. Infrared thermometry experiments show that the optimal injection parameters enhance the gear heat emission by 6.93%. These findings provide support for the heat dissipation study and injection system design for aerospace gears.

Frost propagation and distribution on cold plate surface under forced convection

The characteristics of frost propagation and distribution on cold plate surfaces under forced convection conditions were studied experimentally. The influence of forced convection on frost propagation was analyzed by comparing it with natural convection. The weakening effect of airflow on the frost suppression of the superhydrophobic and groove-superhydrophobic surfaces was revealed. The results indicate that the superhydrophobic micro-nanostructure increases the required volume of the ice bridge, inhibiting the one-way frost propagation from the sample edge to the center. By evaporating the droplets and forming dry zones in the groove valley, the groove patterns can intercept the generation of the ice bridge, and reduce the frost coverage. Under forced convection, the airflow can continuously provide sufficient water vapor to promote the growth of the droplets and trigger isolated-droplet nucleation, thus accelerating the frost propagation by building ice bridge connections in multiple directions. Moreover, the vapor can deposit in the groove valley to prevent the formation of the dry zone, which causes the anti-frosting function of the groove patterns by regulating the local vapor flux to have a limited effect. With the increase of the airflow velocity, the frost morphology changes from spreading columnar crystals to independent ice blocks covered with a frost layer, and the frost coverage rate increases. The frost propagation time drastically reduces, and then rises slightly due to the change in freezing mode and coalescence of the frozen droplets, which are caused by the intenser convective heat transfer.

Quantitative measurement and application of droplets on physical surfaces based on LIF technology

Abstract Contaminated surfaces play a significant role in the transmission of respiratory infectious diseases. To address this issue, we presented a novel quantitative detection method for droplets on physical surfaces, based on the laser-induced fluorescence technique. The proposed detection method was demonstrated in a realistic high-speed train compartment scenario by simulating the process of droplet release during passengers' breathing and coughing. The experimental results showed that this method could offer high precision (10−1 mg/m2) for detecting minute substance concentrations, and its ease of operation makes it suitable for complex engineering environments. The results also revealed that under the combined effects of the indoor airflow and breathing airflow, the range of droplets released by breathing activity exceeded two rows in front of and behind the release position. Simultaneously, we observed that a large number of droplets settled on the seat surfaces on both sides of the same row as the releaser, with over 36% of these droplets concentrated on the backrest area of the seats. As the respiratory jet velocity increased, the location with the most sediment droplets (accounting for 8% of the total sedimentation) occurred on the seat directly in front of the releaser, and approximately 48% of the droplets were found on the back of this seat. Our proposed method overcomes the shortcomings of existing experimental methods in quantitatively capturing the motion characteristics of droplets in complex flow fields.

Electro-blown spinning: New insight into the effect of electric field and airflow hybridized forces on the production yield and characteristics of nanofiber membranes

Electro-blown spinning: New insight into the effect of electric field and airflow hybridized forces on the production yield and characteristics of nanofiber membranes

Study on effects of the train-induced airflow on the temperature field of high-speed railway tunnels in cold regions

Study on effects of the train-induced airflow on the temperature field of high-speed railway tunnels in cold regions

Modeling evaporation with a meshfree collocation approach

In this paper, a new model for the below-boiling point evaporation process with a meshfree collocation method is developed. In order to capture the phase change process, two different approaches are proposed: multi-phase and single-phase. First, a multi-phase approach is considered, where a novel mass transfer model assumes that the diffusion driven by the vapor concentration gradient in the air phase near the interface is the primary driving force for the mass transfer between phases as both the liquid water and air/vapor phases are simulated. Then, a water-only single-phase approach is also proposed, in which only the liquid water phase is simulated. For this, appropriate free surface boundary conditions are developed based on the convective mass transfer theory to model evaporation and incorporate airflow effects without explicitly simulating the air phase. In order to validate the proposed models, a series of experiments with varying air temperature, relative humidity, and airflow rate is conducted. The numerical results show a good agreement with the evaporation rate measured in the experiments. The multi-phase simulations agree better with the experiments, while the single-phase simulations also produce good results with a much lower computational effort.

Pilot scale investigation of DBD-Plasma photocatalysis for industrial application in livestock building air: Elimination of chemical pollutants and odors

Photocatalysis and Plasma are widely considered as efficient and eco-friendly methods for the air treatment at domestic and industrial scales. In fact, the respective application of titanium dioxide (TiO2) and Dielectric-Barrier-Discharge(DBD) drew increasing attention in the last decades for their, flexible, non-selective and high efficiencies for the mineralization and the degradation of large selection of molecules. Nevertheless, the application of these techniques in separate conditions might generate undesired by-products that might hinder their treatment efficiencies. In this study, the effect of combining photocatalysis and Dielectric-Barrier-Discharge (DBD)techniques was investigated for the treatment of livestock building air at laboratory and industrial scale.. of Experiments were conducted in separate (i.e., Photocatalysis or plasma) and combined (i.e., Photocatalysis and plasma) systems to assess the degradation efficiency of two molecules, namely (NH3) and Propionaldehyde (ProPA) under various operating conditions. Studies onducted on laboratory scale showed a interesting level of treatment when applying either photocatalysis or plasma, with degradation yields reaching 29 and 36% for NH3 and 37 and 42% for ProPA, respectively. These degradation efficiencies were further enhanced when combining the processes, thus reaching 72 and 83% for NH3and ProPA, respectively. Moreover, investigations conducted on the generation of ozone during photocatalysis / Plasma treatment showed a decrease in the O3 concentration when compared to separate Plasma treatment. The photocatalytic degradation of ozone under UV radiation and in presence of TiO2 led to Low concentrations of ozone were detected at joint processas a consequence ofits catalytic decomposition under UV-light into HO2°, OH°,O2°-radicals at high humid conditions. The synergetic effect during the pollutant degradation was explained by the association of discharge plasma, presence of O3, UV-light and TiO2..Additionally,The implementation of the photocatalytic-plasma discharge reactor was performed to treat livestock sector air effluent loaded with ammonia.The effect of airflow and relative himidity were assessed. Results showed a significant NH3 removal efficiency in real conditions where it varied between59 and 75% for a flowrate of 2 m2/h and a relative humidity of 100%. Additonnlay, chemical and olfactometric studies were conducted to assess the performance of cimined sytem with real efflluent of livestock building air.

Addressing Water Meter Inaccuracies Caused By Intermittent Water Supply: A Laboratory Investigation of Remedial Measures

AbstractThe interruption of supply in water distribution systems is a common management practice particularly prevalent in developing countries. Upon reopening, the air is expelled through user service pipes, which causes over-reading and seriously impacts the water meter reliability. This paper aims to assess by laboratory tests the effects of air flow on water meter performance by laboratory tests, using a set-up with diameters comparable to those of real water systems. The improvements introduced by applying unmeasured-flow reducer and air valves at different locations are also tested. The relevance of the results of the laboratory activity for practical applications is discussed, both for reducing the over-reading and improving the reliability of the water meters.

A self-intensified inverted evaporation model constructed by high entropy spectrally selective absorber coating (SSAC) for brine water concentration

One strategy proposed before for applying spectrally selective absorber coating (SSAC) is to design separating structure for dividing the photo-thermal layer with steam generation layer. However, this separation concept faces paradox between salt-prevention ability and heat conduction loss, still has huge room for evaporation performance improvement. Herein, we designed an inverted evaporation model which horizontally deploys a high entropy spectrally selective absorber coating (SSAC) by adhering it upon upside of cloth that possessing strong water absorbing capacity. In the function of self-intensified convective airflow effect, this SSAC-assembled inverted evaporation model can achieve super high productivity (4.98 kg m−2 h−1). Resorting to hydromechanics-based analysis method comes to a conclusion that it probably the pressure difference that gives rise to promotion of steam generation, thus realizing the high-efficiency steam generation in inverted evaporation model. By jointly introducing the hanging structure for desalination, the concentrated brine water can be simultaneously collected through dripping from the bottom of the surface without the interface being solid-salt blocked. This work demonstrates the great potential of SSAC-based hanging and inverted evaporation structure for long-term practical desalination and promising application in separation industry.

Numerical Simulation and Optimization of the Airflow Field of a Forage Drum Mower

The repeated cutting of forage can cause grass breakage and affect the performance of the forage drum mower in harvesting forage. Also, it is worth paying attention to the effect of airflow around the cutter on the cutting and feeding processes. To explore the characteristics of the airflow field around the cutter and optimize the key parameters of the airflow, an analysis of the airflow field of the forage drum mower equipped with twisted blades, tilting discs, and guide plates was conducted through numerical simulation. Furthermore, an orthogonal experiment was carried out by using the numerical simulation model. According to the experimental results, the optimal velocity of the airflow for gathering, lifting, and feeding was reached when the disc speed was 2000 r/min, the blade twist angle was 8°, the disc tilt angle was 4°, and the number of guide plates was 2. On this basis, a prediction model of airflow parameters was constructed, and the parameters of airflow around the cutter were measured on a test bench. According to the measurement results, the results of prediction by the model were consistent with the simulation results. Also, compared with the data of airflow measurement, the average error of the model prediction value was −5.83% for the velocity of the gathering airflow, 2.37% for the velocity of the lifting airflow, and 4.20% for the velocity of the feeding airflow, which demonstrates the reliability of the simulation results and prediction model. The results of this research provide a practical reference for the optimal design of the forage drum mower.

Numerical simulation investigation of drug deposition process during nasal administration with auxiliary airflow

Successful delivery of drugs to the Olfactory region (OR) is the key to treating diseases through the nasal cavity. The purpose of this paper is to investigate the effect of auxiliary airflow on particle deposition in the OR during nasal drug administration. A realistic 3D nasal ensemble model was reconstructed from CT scans of the head of a healthy adult. Computational fluid dynamics (CFD) was used to simulate the effect of auxiliary airflow on the deposition of drug particles in the OR during nasal administration. The discrete phase model (DPM) was adopted to track the deposition trajectories of drug particles. Three auxiliary airflows were selected together with three spray cone angles, four particle sizes, five drug particle delivery velocities and three specific injection positions on the deposition fraction of drug particles in the OR were analyzed. The results indicated that the effect of auxiliary airflow on the deposition fraction of drug particles of different particle sizes in the OR is significant. The delivery efficiency of injection position C is always the greatest. A delivery velocity of 15 m/s is more favorable for nasal administration and the effect of spray cone angle is proportional to the auxiliary airflow. Computational results should be helpful for experimental studies and future nasal optimization.

The effect of airflow guiding components on effective ventilation rates in single-sided ventilation applications

Wind-driven single-sided ventilation (SSV) is present in many existing buildings across Europe, and with new near-zero energy building (NZEB) regulations for the refurbishment of the existing building stock, its attractiveness as a noninvasive, low-energy solution is set to continue. As a strategy, however, in addition to its air change rate capacity, the distribution of fresh air is an important evaluation criterion for its performance. Airflow guiding components located in the external opening that enhance the effectiveness of the wind-driven flow in ventilating the occupied zone could improve the quality of indoor environments. To our knowledge, the literature is sparse on the practical implications for ventilation when adopting guiding components such as louvres, an increasingly popular approach. In the present study, the performance of wind-dominant SSV was simulated using RNG and RSM CFD models, with and without louvres at three building orientations, for example, windward, parallel and leeward. The purpose of this study was to investigate whether louvres installed in the opening would improve both the effective ventilation rate and the penetration depth of the flow into the indoor space. The performance of SSV was evaluated using the age of air and interpreting the secondary air circulation inside the room affected by louvres. As a result of these investigations, a newly configured airflow guiding component was designed and compared to the other cases. Results show louvres can play a crucial role in controlling the secondary air circulation inside the room, and they could either improve or worsen the performance of SSV in terms of air-exchange efficiency. It was shown that in most cases, if louvres were the cause of incremental changes in turbulent intensity within the indoor space, then they are effective as an air-exchange efficiency improvement strategy.

Evaluating the effect of unsteady air flow on a slotted aerofoil of wind turbines

Evaluating the effect of unsteady air flow on a slotted aerofoil of wind turbines

MEASUREMENT OF LOCAL CLOTHING INSULATION AND EVAPORATIVE RESISTANCE OF THE HUMAN BODY UNDER FOUR AIR VELOCITY CONDITIONS

This study aims to examine the effect of airflow on local clothing insulation and evaporative resistance. Local clothing insulation and evaporative resistance of two types of summer clothing were measured under four different airflow conditions (0.15, 0.4, 1.0, 2.0 m/s). As a result, evaporative resistance has larger decrease than thermal insulation due to airflow. In addition, the magnitude of decrease in local clothing insulation and evaporative resistance were likely affected by direction of airflow and turbulence intensity.

Modelling of the flotation process by Central Composite Design for obtaining superior grade feldspar

Feldspar is usually found in conjunction with titanium and iron minerals. Feldspar should be separated from other minerals by generally magnetic separation or/and flotation with high grade. However, due to the similarities in the properties, feldspars are difficult to separate from gangue minerals by flotation. In this study, the degradability of iron was investigated by mica flotation, and Central Composite Design (CCD) was used to plan and analyze the results. During the study, the effect of solid ratio, pH, collector amount and airflow on the iron content and the yield of the obtained clean feldspar were modelled. Then, estimation of the optimum conditions and verification tests were performed. The iron content was reduced to 0.14% by mica flotation. However, this reduction amount was found to be insufficient. Finally, iron content was reduced to 0.05%. Considering that the maximum iron content of the superior grade feldspar is 0.1%, it can be said that two stage flotation is successful without different processes such as magnetic separation.

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.

Blowing out a candle from a distance with high amplitude time reversal

Time reversal is a technique that allows the focusing of sound from a source to a remote location causing an impulsive focusing event. Using more sources and other amplitude-increasing techniques, the focusing of audible sound can reach over 200 dB peak. This can extinguish the flame on a single candle without affecting nearby lit candles. Most methods used to extinguish a flame using sound involve the nearfield and nonlinear airflow effects. Because time reversal focusing can occur far from the sources, the mechanism is different. Using high-speed video footage of the focal event, we can see the finer details of this millisecond scale focus interacting with the flame. Measuring the sound field during the focus event at and near the focal location also sheds light on the mechanism. So far, it has been seen that the focus pushes the flame outward, separating the plasma from its fuel source. The known formation of shock waves provides a possible explanation. Further research is being done to explore the cause of the extinguishing of the flame. This talk will show that not only is it possible to focus high amplitude sound waves but targeted flows of air as well.

Experimental and theoretical study on the characteristics of the spill plume in a compartment fire with high-low opposing openings

This paper presents the characteristics of the spill plume in a compartment fire with high-low opposing openings. Three sizes of doors (low openings), six sizes of windows (high openings), and three heat release rates were adopted. Mass flow rates through the openings were calculated with new length scales considering the effect of bidirectional airflow at the door, and then the expression of the neutral plane height was derived. The calculated results had good agreement with the experimental results. To reveal the effect of the opening sizes on the energy proportion, the heat fluxes from the openings were calculated based on the new length scales, and the heat lost through compartment boundaries was also obtained. It was found the size variation of any opening would affect the proportion of each part of the energy and the ratio of heat flow through openings can be represented by the 5/2 power of the ratio of the new length scales. The fire spill plume thickness is related to the horizontal velocity of the plume ejected from the window, and one linear relationship was established. Moreover, the heat flux along the façade and the temperature distribution of the fire spill plume outside the window were given with the new length scale.