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Flexible psammophytes play an important role in controlling soil wind erosion and desertification, owing to their characteristics. Although flexibility of psammophytes has been considered in previous studies, the interaction between flexible psammophytes and the surrounding airflow field still remained unclear. In this study, we used the Young's modulus to describe plant flexibility and conducted a 3D computational fluid dynamics simulation using a standard k-e model and a fluid-structure interaction model. Taking Caragana korshinskii (Caragana), a typical psammophyte, as the research object, we constructed 3D geometric models with different diameters to simulate the airflow field around the flexible psammophytes. By comparing with the simulation results of rigid plants and simulation results of flexible plants at different wind speeds, we could verify the rationality of the simulation method. Based on the simulation results, the maximum swing amplitude of the model and the Young's modulus were found to have a negative correlation, presenting an exponential functional relationship with good fitting. The relationship between the actual Young's modulus of the plant branches and that of different diameter models in the numerical simulation was also established. This study is expected to improve our basic understanding of the interaction between flexible psammophytes and the surrounding airflow field, and provide some qualitative reference for the numerical simulation of the airflow field around flexible psammophytes. [ABSTRACT FROM AUTHOR]

To provide reference for the design of the air-suction tea sorting device, the coupled numerical simulation model was established by the coupling method of computational fluid dynamics (CFD) and discrete element method (DEM) with tea of different quality as test objects, and the model was verified experimentally. Regarding tea particles of different quality, when the test tea particle mass was 0.215, the test value was located in the simulation value with a minimum error of 9 mm, which an error rate of 3.33%, and maximum error of 19 mm, with an error rate of 7.03%. When the test tea particle mass was 0.145, the minimum error of the test value was 5 mm and the error rate was 1.54%, and the maximum error was 9 mm and the error rate was 3.33%. The verification results established the accuracy of the model. During the suspension test and simulation, tea particles were affected by the air flow field of the observation tube, and tea particles fluctuated. During suspension, tea particles were attached to the inner wall of the observation tube under the action of the air flow field. An in-depth study showed that the relationship between the different distances from the initial position of the particles during suspension and the simulation time was a peak function. The extreme function is used to fit the actual trajectory, and the fitting degree is good. The fitting degree of the particle closest to the initial position was 0.9455, and the fitting degree of the particle farthest from the initial position was 0.9981. [ABSTRACT FROM AUTHOR]

The classifier is an essential tool for the development of contemporary engineering technology. The application of classifiers is to categorize mixed-sized particles into multi-stage uniform particle sizes. In current studies, the particles in the classifier obtain their initial velocity when feeding. The classification effect is impacted by the inability to precisely control the initial state of the particles. To solve this problem, a pusher feed classifier was designed in this study, and a numerical simulation was performed to investigate its flow field characteristics and classification performance using the RNG-DPM method. A pusher is utilized to achieve particle feeding without initial velocity and to precisely control the initial state of the particles in the classification flow field. A newly developed two-way air inlet structure is designed to provide a superimposed flow field and enable the five-stage classification. Our results show that this pusher feed classifier has the best classification effect when the vertical airflow velocity is 10 m/s and the horizontal airflow velocity is 3 m/s. Meanwhile, the classification size ratio (CSR) from outlet 1 to outlet 5 was 1.24, 0.55, 0.45, 0.39, and 0.15, respectively. [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]

In order to elucidate the impact of pressurized tubes' structures on the sowing performance of pneumatic seed delivery systems, the EDEM–CFD coupled simulation method was employed to analyze the influence of pressurized tube parameters, including length (L), corrugation depth (S), corrugation width (K), and the number of corrugations, on seed movement characteristics, distribution uniformity, and airflow patterns. Simulation-validated experiments were conducted to study the impact of the optimal pressurized tube structure on seeding performance. The results indicate that pressurized tubes significantly enhance the uniformity coefficient of seed distribution, reduce seed velocity, and decrease the coefficient of variation in distribution uniformity. When pressurized tube parameters, specifically length (L), corrugation depth (S), corrugation width (K), and the number of corrugations, are set at 800 mm, 8 mm, 50 mm, and 6, respectively, the uniformity coefficient of seed distribution exceeds 95%, and the coefficient of variation in seed discharge consistency for each row is less than 3.2%. Moreover, the seed velocity at the outlet of the pressurized tube, the relative velocity of two-phase flow, and pressure loss are all minimal, indicating superior seeding performance. This research provides valuable insights into the analysis of seed movement characteristics within pressurized tubes and the optimization of their structural parameters. [ABSTRACT FROM AUTHOR]

(1) Background: With the rapid development of cloud computing, large AI models, and other emerging technologies, the issue of heat dissipation in data centers has become increasingly prominent. This issue is often caused by inappropriate temperature distribution when using cold air to cool servers. Improving temperature distribution is key to optimizing the thermal performance of data centers. Previous solutions do not include installing adjustable underfloor deflectors under a raised floor while adjusting the aperture ratio of the floor grille and replacing the side of the floor grille located near the air-conditioning unit with a fan floor. (2) Methods: A 3D model of a data center was established, and its meshing and boundary conditions were set. The airflow inside the data center was analyzed using a CFD simulation to assess the temperature distribution resulting from two proposed solutions. (3) Results: Simulations and analyses showed that both options balanced the airflow close to and away from the conditioned side cabinets. This maximized the cooling capacity and improved temperature uniformity. The maximum temperature drop registered for the average cabinet's out temperature was 2.81 °C. And by installing an adjustable underfloor deflector under the floor grille in rows O and N and adjusting the grille opening, the airflow to the cabinet near the air-conditioned side increased by 18.1%, and the airflow away from the air-conditioned side decreased by 5.1%. Similarly, replacing the Q-row floor grille with a fan floor resulted in a 4.9% increase in airflow to the cabinet near the air-conditioning side and a 3.8% decrease in airflow to the cabinet away from the air-conditioning side. (4) Conclusions: Airflow is a crucial factor that affects cabinet temperature. And balancing airflow between the front-end and rear-end cabinets is essential to make the best use of the cooling capacity and improve temperature distribution within data-center cabinets. This can be achieved by installing a fan floor and an underfloor deflector device in front of high-temperature cabinets located near air-conditioning units. [ABSTRACT FROM AUTHOR]

To address the challenges of missed and disorderly picking in tea harvesters, this study focused on the leaf-collection pipeline and utilized Fluent simulation 19.0 software. A single-factor test identified key parameters affecting airflow velocity. An orthogonal test evaluated the main pipe taper, number of branch pipes, and branch pipe outlet diameter, with average outlet wind speed and wind speed non-uniformity as indicators. The optimal parameters were a main pipe taper of 25.5 mm, 10 branch pipes, and an inner diameter of 17.10 mm for the outlet, resulting in 10.73 m/s average wind speed and 8.24% non-uniformity. Validation tests showed errors under 1%. Further optimization on the internal structure's extension length led to 11.02 m/s average wind speed and 8.04% non-uniformity. Field experiments demonstrated a 3.40% stalk leakage rate and 90.36% bud leaf integrity rate; the optimized structure of the leaf-collecting pipeline significantly improved the uniformity of airflow and the picking efficiency. These findings offer valuable insights and practical benefits for enhancing the efficiency of tea harvesters. [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]

Noise reduction structures are important for the vibration and noise reduction design of aerospace engines. The design of noise-reducing structures often needs to be quickly evaluated via numerical simulations. Hence, the simulation results of the corresponding system are very important for guiding the design of noise-reducing structures. High temperature is one of the key environmental factors that need to be considered when evaluating the sound attenuation process via numerical methods. In this study, numerical simulations of acoustic wave propagation on an acoustic liner structure considering air temperature variations are carried out by using compressible Navier–Stokes equations and the ideal gas equation of state. The results showed that the effect of temperature on sound attenuation under grazing flow conditions is complex. Moreover, an increase in temperature will reduce the transmission loss of the acoustic liner in the grazing flow at high air speed. [ABSTRACT FROM AUTHOR]

The high-quality flow field of an aeroengine ground test cell is the basis for accurate and reliable engine testing and obtaining relevant performance data. In this study for a U-shaped ground test cell, first, the similarity dimension analysis between the original model and the 1∶10 scaled model is conducted to verify the accuracy of the numerical simulation of the scaled model. Then, the parametric numerical simulation method is used to study the effects of the augmentor's diameter and the distance between the engine jail nozzle and the augmentor inlet on the aerodynamic flow field of the ground test cell for the 1∶10 scaled model. The results show that if the diameter of the augmentor tube is too large or too small, the flow rate of the bypass airflow in the augmenter will decrease; thus, the average temperature of the exit section will increase. At the same time, the change of airflow exhaust speed in the blast basket can effectively affect the uniformity of airflow in the silencing tower. With the increase of distances between the engine jail nozzle and the augmentor inlet, the ejection effect of the engine tail jet enhances, but the exhaust velocity in the blast basket decreases; accordingly, the quality of the flow field in the silencer tower significantly deteriorates with the tendency of the vortex centers on both sides of the pipe moving upward. In Case4 , the airflow velocity at the front chamber inlet of the test workshop is significantly higher than that of the baseline model, Case0 , and the ejection ratio increases by 19.4%. [ABSTRACT FROM AUTHOR]

This article deals with the development of small-sized wind power equipment as a viable solution for decentralized renewable energy production. To improve operational specifications of conventional turbine models with rotating blades, it is proposed to use a new design of wind power plant synthesized on the base of a closed loop conveyor equipped with flatshaped blades. In this design, blades are mounted on a belt with an opportunity to move together with it in one straight line direction. Air flow interaction with flat blade that performs translation motion is studied by computer simulation using a superposition principle. In accordance with this approach, a fast-chaotic motion of air particles (Brownian motion) is separated from the slow-directed air motion, with the given average velocity. Dynamic analysis of flat blade interaction with air flow is performed for the stationary air flow with constant speed and also for non-stationary flows with wind gusts. Optimization of the system parameters is made using the generated power as a criterion. Simulation results confirm the serviceability and efficient operation of the proposed conveyor type wind power equipment. It can be mounted on the roofs of buildings or rooftops of vehicles, also device is befriended to nature and people. [ABSTRACT FROM AUTHOR]

A numerical model of single-particle fog-dust collision coupling in a high-speed airflow based on three-phase flow theory. The effect of the fog-to-dust particle size ratio, relative velocity between the fog and dust particles, collision angle and contact angle at the wetting humidity function of dust particles is investigated. Different particle size ratios are determined for achieving the optimal wetting humidity for the interaction of high-velocity aerosols with dust particles of different sizes, for differ, that is, kPM2.5 = 2:1, kPM10 = 3.5:1 and kPM20 = 1.5:1. The optimal humidity increases with the relative velocity U between the fog and dust particles in the high-speed airflow. The larger the collision angle is, the lower the wetting rate is.The smaller the contact angle between the solid and liquid is, the better droplet wetting on dust is. The fine kinetic mechanism of single-particle fog-dust collision-coupling in a high-speed airflow is elucidated in this study. [ABSTRACT FROM AUTHOR]

A new type of gust generator generates the airflow oscillation in the wind tunnel through the Coanda effect of the unsteady trailing edge blowing, which has been shown to have strong potential for accurately simulating discrete gusts. It is necessary to study the relationship between the generated gust characteristics and the control parameters of such devices in order to optimize the design performance and improve gust simulation capabilities. By solving the compressible unsteady Reynolds-averaged Navier–Stokes (URANS) equations, the computational fluid dynamics model of the subsonic airflow past the gust generator in the wind tunnel was presented. The effects of jet momentum, frequency, and spanwise blowing ratio on gust intensity, shape, and spatial uniformity were investigated. Results indicate that the intensity of gusts is positively correlated with jet momentum and frequency. The gust shape matches well with the normalized jet momentum coefficient curve. However, when the frequency increases to above 10 Hz, the gust shape differs significantly from expectation due to the appearance of reverse wave peaks. In addition, the mechanism of the impact of the sidewall and partial spanwise blowing on gusts was revealed. In the three-dimensional situation, streamwise vortices are formed on the sidewall and at the spanwise position where the blowing stops, respectively. This results in an increase and noticeable nonuniformity in gust amplitude. When the blowing with a 15% spanwise length near the sidewall is turned off, the gust amplitude at the symmetry plane increases by nearly 40% due to the main vortex being closer to the main flow. The result provides a physical explanation for the availability of this operation to reduce gust attenuation. [ABSTRACT FROM AUTHOR]

Pumping airflow occurs in single-sided natural ventilation buildings when the openings are located on the leeward side; the direction of airflow through the building then changes periodicity. In order to propose a calculation method of the ventilation rates for single-room buildings and analyze the pumping ventilation for multi-room buildings, the CFD method with an SST k-ω turbulence model was used to conduct numerical simulation in this study, which is verified by other experimental results. Firstly, the qualitative and quantitative characteristics of pumping ventilation were investigated for a single-room building with two openings. The results show that the steady-state method underestimates the ventilation flow rates, and the unsteady-state method captures the microstructures of the flow better. Secondly, the vortex-shedding and indoor airflow oscillation frequencies were analyzed based on transient simulation for a single-room building. It was found that both of them increase with air speed. Then, the factors affecting ventilation flow rates were analyzed. A calculation method for dimensionless ventilation rates is proposed. Finally, the pumping ventilation for a multi-room building was numerically simulated. The ventilation rate for a middle room is greater than that for a corner room, and the ventilation rate for any room in a multi-room building is greater than the single-room building given the same room size and the same incoming wind speed. The findings of this paper are helpful for the design and evaluation of natural ventilation. [ABSTRACT FROM AUTHOR]

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To improve its cleaning performance, the peanut sheller's air–screen cleaning device was used as the research object, and a numerical simulation was carried out. A scheme was proposed to optimize the installation angle of the screen surface of the air–screen cleaning device, and the influence of the airflow velocity of the sieve surface before and after the structural improvement of the machine on the airflow distribution of the whole chamber was evaluated. At the same time, the computational fluid dynamics–discrete element method (CFD–DEM) of coupling simulation was used to carry out single-factor simulation tests on the improved air–screen cleaning device, analyze the movement trajectory, velocity, and displacement of the extrudates in the cleaning chamber, characterize the separation law of extrudates, and determine the parameter ranges for each factor. In addition, based on the central composite Box–Behnken design, an orthogonal simulation test was carried out with three factors, including fan speed, amplitude, and vibration frequency, and the influence of each factor on the kernel loss rate and impurity rate was investigated. Furthermore, the influencing factors were optimized, and the optimal parameter combination was obtained; when the fan speed was 1682.72 r/min, the amplitude was 3.74 mm, and the vibration frequency was 492.86 Hz, it was more conducive to the cleaning of kernels. Finally, the accuracy of the simulation and optimization methods was verified via the machine test, and the optimal parameter combination was obtained: at a fan speed of 1680 r/min, an amplitude of 3.7 mm and a vibration frequency of 490 Hz were achieved, and the kernel loss rate and impurity rate were 2.01% and 2.42%, 3.71 and 4.42 percentage points lower than those before optimization, respectively. [ABSTRACT FROM AUTHOR]

In response to the issue of suboptimal thermal performance in traditional data centers, four distinct airflow management structures, namely, composite, linear, convex, and concave diversion plates, were proposed. Utilizing Airpak 3.0, numerical simulations were conducted on five different data centers, including the original configuration of the computer room air conditioner (CRAC). The objective was to assess the impact of various airflow management structures on the thermal performance of data centers, with experimental validation of the model. The findings demonstrate that these airflow management structures significantly enhance the thermal performance of data centers. Among them, the composite diversion plate yielded moderate improvements, the convex diversion plate effectively optimized velocity distribution, although with limitations in temperature optimization, and the concave diversion plate exhibited non-uniform temperature distribution. Overall, considering all factors, the linear diversion plate proved to be the most effective. [ABSTRACT FROM AUTHOR]

Lagrangian stochastic models (LSM) are widely used to model the dispersion of sea spray droplets injected from the water surface into the marine atmospheric boundary layer (MABL) and for evaluation of the spray impact on the exchange fluxes between the atmosphere and the ocean. While moving through the MABL the droplets pass through the region of high gradients of air velocity, temperature and humidity occurring in the vicinity of the air–water interface. In this case, the applicability of LSMs constructed under the assumption of weakly inhomogeneous flows is questionable. In this work, we develop a Lagrangian stochastic model taking into account the strongly inhomogeneous structure of the airflow in MABL and, in particular, the anisotropy of turbulence dissipation rate. The model constants and the diffusion matrix coefficients are calibrated by comparison of the LSM prediction for the profiles of droplet concentration and the exchange fluxes of sensible and latent heat against the results of direct numerical simulation of turbulent, droplet-laden airflow over a waved water surface. [ABSTRACT FROM AUTHOR]

The closure of deep mines, featuring multi level seam extraction, lasts many years. During this time period, the ventilation system must ensure adequate working conditions, and ensure the safety and stability of fan operation in gas and fire hazards conditions. The analysis of air flows and methane inflows during the progress of mining mine excavations closure, is the primary object of the article. Execution of such analysis requires knowledge of the mining mine excavations' closure schedule, the structure of the ventilation system under consideration, the values of the parameters describing the air flows delivered to the mine excavations, and the current characteristics of operating fans and predicted methane exhalation. A computer database, currently being updated by a mine ventilation department for the VentGraph-Plus computer software, has been used simulate the various ventilation scenarios experienced, during the final stage of closure, including the shutdown of the main fans and the backfilling of shafts. The results of case study, containing 2 variants of simulated examples, are presented in the form of diagrams of methane concentration changes in time at characteristic places of the mine. The completed simulations of ventilation processes during the closure of mine excavations and transfer of inflowing methane, indicate useful possibilities of the computational tool used. [ABSTRACT FROM AUTHOR]

Background and Objectives: This paper presents a unique study that links the physical conditions in the nasal passage with conditions that favour the development of bacterial strains and the colonization of the mucous membranes of the nose and paranasal sinuses. The physical parameters considered were air flow, pressure, humidity, and temperature. Materials and Methods: Numerical models of the human nose and maxillary sinus were retrospectively reconstructed from CT images of generally healthy young subjects. The state-of-the-art numerical methods and tools were then used to determine the temperature, humidity, airflow velocity, and pressure at specific anatomical locations. Results: The results were compared with optimal conditions for bacterial growth in the nose and sinuses. Conclusions: Temperature, humidity, air velocity, and pressure were shown to play critical roles in the selection and distribution of microorganisms. Furthermore, certain combinations of physical parameters can favour mucosal colonisation by various strains of bacteria. [ABSTRACT FROM AUTHOR]

The main cable of suspension bridges is subject to corrosion and requires advanced anti-corrosion technology. Consequently, the internal airflow of the main cable has become a significant research focus. This study employs image processing and machine learning to analyze the cross-sectional images of the main cable and reveals the distribution characteristics of pores and fractures within the main cable cross-section. The numerical simulation model of the main cable is divided into inner and outer parts based on porosity, with porosity levels of 18.16% and 32.11%, respectively. Fractures randomly occurred in the inner part, with a probability of 31.37%. A simulation model based on fractured porous media (FPM) is developed, which innovatively incorporates the fracture flow model into the numerical simulation of the internal airflow of the main cable. The numerical simulation clearly explores the intricate details of the internal flow field of the main cable, revealing that the existence of fractures has a great impact on the internal flow field of the main cable. Additionally, the relative deviation of specific frictional head loss between the field experiment and numerical simulation is about 6.83%, indicating that the numerical simulation results are relatively reliable. [ABSTRACT FROM AUTHOR]

With the spread of sustainability concepts, due to the global energy crisis and the unrestrained consumption of natural resources, the importance of rational use and reduction of energy consumption has been intensified, albeit in short steps. This concern has taken up bioclimatic concepts in buildings, especially housing buildings for low-income people, aiming at improving the quality of housing production in terms of its habitability. The objective of this research is to theoretically and experimentally study the natural ventilation in a housing building, which fits into the low-cost pattern. The use of Computational Fluid Dynamics to predict natural ventilation was adopted as a tool to perform these analyses. Experiments were carried out by visiting the study area to collect data on air velocity, temperature, and relative humidity in all rooms of the residence in order to carry out the intended analyses. Computer simulation of natural ventilation considering the building with the doors and windows open and with fixed geometry was performed. Results proved that the proposed mathematical model was able to reproduce, with rich details and physical coherence, the internal and external air flow inside the building, indicating better internal ventilation performance in environments that have door and window openings, with recesses, revealing the importance of cross ventilation to reduce the internal temperature and consequent improvement in thermal comfort. The idea is to help civil engineers and specialists in the economically viable design of low-cost buildings from the economic, social, and thermal comfort points of view. [ABSTRACT FROM AUTHOR]

The higher the pointing accuracy of the radio telescope, the more obvious the influence of wind disturbance on antenna performance. Taking the site of the 110 m aperture QiTai radio Telescope (QTT) as an example, the terrain and air flow characteristics of the site are studied. It is found that the wind direction with high incoming wind frequency and relatively high speed is mostly located in the mountain gap on the periphery of the antenna. If the wind resistance facilities are precisely arranged in the upstream tuyere, the wind speed in the antenna area can be effectively reduced. This study proposes a method to control the wind flow at a telescope site based on the precise arrangement of the windbreak fence. The windbreak fence simulation model is constructed using the theory of porous jump. The mean error of the simulation results is less than 14% compared to the wind tunnel measured data, indicating that the constructed windbreak fence model has high reliability. The computational domain model of the working conditions for the site is constructed. The extreme condition of the windbreak fence arrangement is considered, and the simulation results show that the wind speed in the antenna area can be reduced by more than 30% through the control of the windbreak fence. It verifies the feasibility of the method of controlling the wind flow by the windbreak fence for the site which provides a reference for the subsequent research on the precise arrangement of the windbreak fence. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Tree is an essential factor affecting airflow and pollutant diffusion in the urban street canyon. The wind environment in the urban street canyon will be effectively improved by expounding the mechanism and implementing greening measures. Moreover, it will help decrease the pollutant concentration around the street canyon. This paper reviews the airflow and pollutant diffusion numerical simulation in the street canyon under the tree influence. Firstly, the numerical mathematical model used for pollutant diffusion and airflow in urban street canyons under the influence of trees is summarized. The representation of trees' numerical mathematical model in the simulation domain is mainly proposed. Secondly, the wind environment and pollutant distribution factors influencing urban street canyons are elaborated and analyzed, including tree characteristics, layout, street canyon shape, and thermal. Furthermore, current research progress and deficiencies are discussed. Finally, the future research direction of wind environment and pollutant distribution simulation in urban streets under the influence of trees is pointed out. [ABSTRACT FROM AUTHOR]

Loading a dielectric barrier discharge plasma excitation on a Savonius wind turbine can improve its performance. To study the mechanism of performance improvement, the effects of three pairs of plasma excitations at different positions were comparatively studied by means of numerical simulation, and it was found that the middle position was the best for plasma excitation loading. Then, two plasma excitations in opposite directions were set at this position, and the effects were compared. The results show that plasma excitation can generate a high-velocity airflow, which can affect the velocity distribution around the blade, thereby changing the pressure distribution, and therefore the performance of the Savonius wind turbine. The effect of two opposite directions of plasma excitation loaded at the optimum position on the performance of the wind turbine varies with the change of the TSRs. When the TSR is relatively small, the influence of the two directions is very different. While the TSR is relatively large, the influence of the two directions is close. [ABSTRACT FROM AUTHOR]

There is a significant amount of dust during tunnel construction. As a comprehensive prevention method for tunnel dust, dust collector technology has been widely used in tunnel construction. The flow field distribution in a dedusting equipment cabin directly affects the treatment efficiency of tunnel dust. In this study, using a dedusting equipment compartment with 5 (in row) × 20 (in column) filter cartridges (FCs, diameter of 0.35 m) as the research object, the effects of air-intake mode, position, and other parameters on the airflow rate of FCs inside the cabin, and indoor air distribution characteristics were studied using a numerical calculation method, which was verified by an experiment. The results indicated that for the cabin with only an end air-intake, the length of the cabin cannot be too long, as this would cause a low airflow rate of the FCs located at the center of the cabin. Furthermore, the effects of setting a baffle and grille on the total airflow rate of the FCs inside the cabin with only an end air-intake was more significant than that with both an end air-intake and side air-intakes, the difference of the total airflow rate among them can be up to 59%. Setting a baffle at the end of an air-intake significantly reduced the total airflow rate of the FCs about 59%, which was significantly increased about 5% by setting grilles. Additionally, the side air-intakes improved the total airflow rate of the FCs more than the end air-intake by about 24%, but the intake efficiency of the former was lower than that of latter by about 61%. Finally, based on cabins with only an end air-intake, setting the side air-intakes on the cabin where the airflow rate of FCs is low, can significantly improve the total airflow rate of FCs in the cabin, particularly the FCs around the side air-intakes, the increase here can reach 36% compared with other locations. [ABSTRACT FROM AUTHOR]

Featured Application: In this study, a computational fluid dynamics (CFD) model was developed for a pregnant sow piggery with centralized ventilation to reveal the distribution of temperature, humidity, and airflow velocity. After verifying the CFD model, the location of the air outlets and the velocity at the air inlets was also examined to obtain the optimal structure and control parameters. The average values, non-uniformity coefficient, and comfort levels were used to evaluate the performance of the piggery under these different parameters. (1) Background: The thermal environment in a pregnant sow piggery is affected by physical parameters such as air temperature, relative humidity, and airflow velocity. However, it is challenging to conduct experimental studies due to the high cost. (2) Methods: Computational fluid dynamics (CFD) was used to study the distribution characteristics of airflow in a pregnant sow piggery with centralized ventilation. (3) Results: The results show that the maximum difference between the simulated and experimental temperature was less than 1.54 °C, and the simulated and tested relative humidity difference was less than 10% RH. Incorporation of a middle air outlet is beneficial for increasing the uniformity of temperature distribution, as studied by comparing the temperature and humidity uniformity coefficient of the two air outlet locations, but the uniformity of humidity distribution will be reduced. With an increase in velocity, the temperature shows a downward trend and the relative humidity shows an upward trend. (4) Conclusions: The most suitable position for the outlet is the middle, with an associated airflow velocity of 0.5 m/s. This study revealed the variation in flow field distribution and air distribution in the pregnant sow piggery as a consequence of changes in ventilation structure, which has certain significance as a reference for the optimization of airflow in intensive pregnant sow piggeries. [ABSTRACT FROM AUTHOR]

By taking a 130 t/h water-cooled grate biomass boiler as the research object, the ANSYS software is applied to simulate the effects of the tail burnout air's incidence angle, wind speed, and pipe diameter on flow field distribution in the furnace, the movement of unburned carbon particles at the tail of the grate under cold operation. The influence rules of the incidence angle, pipe diameter, and wind speed of the tail burnout air on the combustion in the furnace and the movement of the tail particles were obtained. The results show that the setting of burnout air at the tail of the grate can better organize the air flow field at the grate tail, change the particle distribution, prevent small density particles from directly falling into the ash hopper, and prolong the residence time of particles on the grate. Under the study conditions, with an increase in the outlet velocity and the pipe diameter of the tail burnout air, as the movement degree and the burnout degree of grate particles increase, the boiler efficiency increases. With an increase in the incidence angle of the tail burnout air, the flow field in the furnace and the reduction ratio of the tail particles increases at first and then decreases, and the optimal incidence angle is 11–13°. [ABSTRACT FROM AUTHOR]

Results of numerical simulations of turbulent reacting flows in a channel with sudden expansion with due allowance for injection of hydrogen jets into a supersonic (M = 4) air flow are reported. The simulations are performed in a three-dimensional unsteady formulation with the use of the ANSYS Fluent software under the conditions of experiments performed in the IT-302M high-enthalpy wind tunnel. The computations predict a self-oscillatory regime with intense oscillations of pressure and integral heat release. The period-averaged pressure distribution is in reasonable agreement with the experimental measurements, and the frequency of pressure oscillations is within the range obtained in the experiments. Based on a detailed analysis of the flow characteristics within the full cycle of oscillations, the feedback mechanism responsible for the emergence of self-supported oscillations is refined. [ABSTRACT FROM AUTHOR]

The coexistence of developed areas and historic buildings is an important topic in urban planning. Our study focuses on this topic from the perspective of urban microclimate. A multi-physics CFD simulation is applied to model urban microclimate with anthropogenic heat and buoyancy effects. First, we clarified the impact of new development, i.e., high-rises on pedestrian-level air flow by comparing city structures in Case A (the past, 1960s) and Case B (the current, 2020s). The results showed an average wind speed decrease of 43% over time. Second, we assessed air temperature increments from anthropogenic heat emitted from Case C (high-rises), Case D (historic buildings), and Case E (both). We found that the mean air temperature increased by 0.16 °C for Case C, 0.52 °C for Case D, and 0.87 °C for Case E, respectively. Third, we developed heat mitigation strategies based on the assessment results in the previous steps. The integration of open spaces and building porosity, which create wind corridors together, can promote outdoor ventilation and heat dispersion in the study area. Compared with Case E, the three mitigation cases improve outdoor thermal environment, with mean temperature reductions of 33%, 25%, and 21%, respectively. Finally, we developed new mitigation strategies by considering the constraints in this special region, where modernity and history coexist. Our practical mitigation strategies will aid urban planning and support conservation efforts not only in Singapore, but also in other tropical and subtropical cities. [ABSTRACT FROM AUTHOR]

This paper deals with a dual design device for wind energy production, in which the movement of the blade consists of several stages, that is, two stages of rotation about two fixed axes and two stages of the blades straight translation movement. The proposed design offers a closed-shaped flattened conveyor equipped with several identical flat-shaped blades. The blades are mounted on a conveyor belt and have an opportunity to move together with the belt in one straight line direction. Therefore, air flow kinetic energy is transformed into translation motion of flat blades. The conveyor system has a built-in energy generator. To analyse blade interaction with air flow, a superposition principle is applied, in which the fast chaotic motion of air particles (Brownian motion) is separated from the slow flow motion with the given average velocity. On the base of such separation, a differential equation of motion for the entire conveyor system with one degree of freedom is obtained. Dynamics of the system due to the action of air flow is simulated with computer program Mathcad. Optimization of system parameters is performed, using a generated power as criterion. In addition, motion control at changeable airflow is optimized by selecting the blade orientation and corresponding adjustment of generator. [ABSTRACT FROM AUTHOR]

Background: The truncation level of human airways is an influential factor in the analysis of respiratory flow in numerical simulations. Due to computational limitations and limited resolution of diagnostic medical imaging equipment, a truncated geometry of airways is always investigated. Objective: This study aimed to employ image-based geometries with zero generation and 5th-generation truncation levels and assess bronchial airways truncation's effect on tracheal airflow characteristics. Material and Methods: In this numerical study, computational fluid dynamics was employed to solve the respiratory flow in a realistic human airway model using the large eddy simulation technique coupling with the wall-adapting local eddy-viscosity (WALE) sub-grid scale model. The accuracy of numerical simulations was ensured by examining the large eddy simulation index of quality and Kolmogorov's K-5/3 law. Results: The turbulent kinetic energy along the trachea has increased abnormally in the geometry with the zero-generation truncation level, and more severe fluctuations occurred in the velocity field of this geometry, which increased the tendency of each point to rotate. Compared to the extended model, the airflow's more chaotic behavior prevented larger-scale vortices from forming in the geometry with the zero-generation truncation level. Larger-scale vortices in the extended model caused the primary flow passing next to the vortices to accelerate more intensely, increasing the wall shear stress peaks in this geometry. Conclusion: Eliminating the bronchial airways caused changes in tracheal airflow characteristics. [ABSTRACT FROM AUTHOR]

Purpose. Due to the poor ventilation and air stagnation in the radiation therapy ward, it is easy to cause respiratory disease transmission, which brings about the public health safety problem of infection. In order to alleviate this problem, we propose a research method based on computational fluid dynamics (CFD). Method. A three-dimensional model of a radiation therapy ward is established, and the CFD software framework is used to numerically simulate the air flow field in the constrained radiation therapy ward environment. We computed the influence of the spray speed, particle size, and inlet content of respiratory droplets on the flow and spread of multidrug-resistant bacteria. Results. In the range of the horizontal transmission line X from 0 to 3 meters, when the transmission speed (V) is 35 m/s, the multidrug-resistant bacteria concentration reaches the highest value. In the range of the vertical transmission line Y from 0 to 3 meters, when V is 35 m/s, the multidrug-resistant bacteria concentration reaches the highest value. Conclusion. A large amount of data shows that there is a positive correlation between the respiratory droplet spray velocity, inlet content, and the multidrug-resistant bacteria flow propagation speed and concentration distribution. The respiratory droplet size mainly affects the peak concentration of the multidrug-resistant bacteria flow propagation. [ABSTRACT FROM AUTHOR]

In this paper, three types of air guide vanes are designed: direct-type, L-type, and logarithmic spiral type, respectively. ANSYS-FLUENT 20.0 is used to numerically simulate the internal flow field of turbo air classifier by novel different structures. The numerical results show that the guide vane structures have a good effect on the flow field stability of the annular function zone in the classifying chamber. The distribution of tangential velocity and radial velocity verified the logarithmic spiral guide vane, and makes the airflow flow along the rotor cage circumferentially uniformly. In addition, the turbulent dissipation rate and energy loss decreases in the rotor cage region, which also shows that the guide vane is beneficial to improve classification performance. The tromp curve of the numerical simulation shows that the logarithmic spiral guide vane reduced the cutting size by 6.3% and 23.7% at two different process parameters, and is obviously better than other guide vane structures in improving the classification sharpness index (K). Finally, the reliability of numerical simulation is verified by material experiment. The research results have certain theoretical significance and guidance for the structural design of the guide vanes of the turbo air classifier. [ABSTRACT FROM AUTHOR]

Copyright of Railway Standard Design is the property of Railway Standard Design Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Railway Standard Design is the property of Railway Standard Design Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

A mathematical model of the process of unsteady conjugate heat transfer of a thermionic thermal protection system during supersonic air flow around a spherically-blunted cone is investigated. Estimates of the effect of evaporation (emission) of electrons from the emitter surface on lowering the temperature of the composite shell of the thermoelectronic thermal protection are made. The influence of different angles of attack on heat transfer modes in the system of multielement thermionic thermal protection has been studied. Qualitative agreement of calculated results with the known data has been found. [ABSTRACT FROM AUTHOR]

We performed numerical simulations of the particle mass transfer rates on the horizontal and vertical thermally active rough walls confining a turbulent natural convection flow. We considered the air flow conditions in a cubical cavity (L = 1.22 m , R a = 5.4 · 10 8 , Pr = 0.71) with two opposed pairs of consecutive walls at different temperatures, for which measurements of the particle deposition velocities are reported in the literature. The simulations were carried out by solving the momentum, thermal energy and particle mass transfer equations using a series of two-dimensional computational cell units to determine spatial evolution and development of the particle concentration boundary layer in the vicinity of hot and cold rough walls. Different flow conditions, wall orientations, sizes of roughness elements, particle diameters and temperature increments between the wall and the bulk fluid, typically found in indoor environments, have been considered and consequently, results can be used to estimate the particle deposition rates in real scenarios. At large mass transfer particle Péclet numbers, corresponding to spherical particles with diameters of 0.5–1 μm, the wall mass transfer rates of particles on rough textures typically increase by a factor of about 3 in comparison with the deposition on smooth surfaces. The thermophoretic effect significantly decreases the particle deposition on hot surfaces and increases it on cold surfaces, especially at large particle Péclet numbers. The numerical predictions of the deposition velocities are in good agreement with the measurements reported in the literature for the same flow conditions considered. [ABSTRACT FROM AUTHOR]

The mining in seams with a high methane content by means of a longwall system, under conditions of high extraction concentration, results in exceeding methane concentrations allowed by the regulations at workings of the longwall environment, with the effect of mining machines' standstill periods. The paper is a part of a study supporting the development of a system for shearing cutting speed control at the longwall, which should substantially reduce the production standstills due to exceeded limits and switching off the supply of electric equipment. Such a control system may be appropriate for longwalls ventilated using "Y" and "short Y" methods. Efficient Computer simulations of the 3D airflow and methane propagation may assist the design and initial evaluation of the control system performance. First chapters present studies that are necessary for a proper formulation of the properties of the longwall model. Synthetic analysis of production during the period of longwall operation allowed one to choose the input assumptions to carry out ventilation-methane computations in a CFD numerical model of longwall Z-11. This study is followed by a description of the model that is used for a case study, considering three variants of the shearer position. Finally, initial simulation results and directions of further studies are discussed. [ABSTRACT FROM AUTHOR]

Computer simulations of three different geometries of thermoelectric generator (TEG) appliances have been carried out to calculate the maximum power generated by a single TEG and the maximum total power generated by all the TEGs in the geometries. Among these three geometries, every aspect was the same except the number of TEGs, so the density of the number of TEGs facing hot flowing air was varied. We used single-TEG, three-TEG, and five-TEG models. Simulations were carried out at 120 °C for the hot flowing air and at 42 different cold side temperatures to see the effect at different temperature differences. We showed the effect of the density of the TEG number on the maximum power generated. Powers generated by a single TEG from each geometry and the total generated powers in different geometries are compared. We have used the results we obtained to calculate the total electric energy generated by these TEGs in the wall of an industrial chimney for a six-month duration (between October 2017 and April 2018 in the winter season) by using real daily temperature data at a chosen site (the city of Kırıkkale) taken from the Turkey Meteorological Institute. [ABSTRACT FROM AUTHOR]

The efficiency of air heat accumulation by a granular nozzle of a soil regenerative heat exchanger and the possibility of modeling the processes of thermal front propagation along the nozzle length over time are investigated. One of the options for the use of a regenerative apparatus with a dense layer, for which the heat source is solar radiation, and the regenerator itself is designed to maintain the required temperature climate in greenhouses. The results of the pilot installation test in field conditions are given. The temperature distribution curves along the length of the heat exchange channel for different moments of heating time of the granular nozzle are obtained. A study of the process of heat transfer between air flow and the share of gravel in the channel. It is established that the differences in wall and particle temperatures are insignificant, as a result of which the error of temperature measurements on radiation can be neglected. It was found that the heat accumulated by the particle was transferred to the environment for a long time, which indicates the rationality of the use of gravel as a granular nozzle for regenerative heat exchangers. The analysis of the course of curves on the surface of the particle and in the middle is carried out. It is determined that the law of temperature change is the same for all points of the particle. Computer simulation of the process of heating a dense layer of particles in the heat exchange channel has been performed. The analysis of temperature distribution along the length of the heat exchange channel for different heating periods is carried out. Computer simulations have been shown to be able to predict the rate of thermal front propagation for arbitrary output data and to determine, depending on the conditions of use, the geometric characteristics of the duct and operating parameters such as temperature and air flow, duration of heating and cooling periods. [ABSTRACT FROM AUTHOR]

Once a fire occurs in a long curve tunnel, the mixing of hot smoke flow and cold air leads to turbulence due to the curvature's impact. This phenomenon results in a greater thermal pressure difference at the fire source and a substantially greater temperature field than in the straight tunnel. The longitudinal air flowing along the wall loses a lot of velocity in the curve tunnel due to the massive wall friction. Under the same fire extinguishing conditions, the curve tunnel and straight tunnel have different requirements for longitudinal ventilation. Factors such as tunnel curvature, longitudinal ventilation operation time, and ventilation velocity were all evaluated in order to investigate the influence of longitudinal ventilation parameters on the fire extinguishing effect of water mist in the curve tunnel. The fire extinguishing effect of water mist coupling with longitudinal ventilation in the curve tunnel is studied by numerical simulation, and the recommended values of ventilation operation time and ventilation velocity in the curve tunnel with the participation of the water mist system are given. The results show that (1) the fire extinguishing effect of water mist decreases with the increase of curvature under longitudinal ventilation and (2) fire prevention effect is best when water mist and longitudinal ventilation are used in the curved tunnel, and the ventilation velocity should be greater than 2 m/s. [ABSTRACT FROM AUTHOR]

Flat air solar collectors are used for heat transfer between the absorber and the heat transfer fluid, to improve this transfer there are several methods. Among these methods, the exchange surface lengthening and the creation of turbulence. In this work is done to give a comparison between two types of solar collectors, so we have made an improvement of Ben Slama Romdhane's solar collector by creating two air flow passages to increase heat transfer. We made a 3D simulation of a flat air solar collector with transverse baffles which causes turbulence and increases the exchange surface; we use the ANSYS calculation code to make the simulation and gives results with a brief time and minimal cost. [ABSTRACT FROM AUTHOR]

Achieving an optimal cooling of the generator unit is indispensable for high working performance. In this work, computational fluid dynamics analysis on the flow field of the conventional type and silent type of the S688CCS series generator unit is conducted, and design optimization of the generator unit with poor cooling is studied based on flow field analysis results. Flow field simulation results indicate that the total cooling air quantity of the silent type generator unit is lower than that of the conventional type generator unit, and the cooling air quantity of the radiator is also lower than that of the conventional type generator unit, which is not conductive for the cooling of the silent type generator unit. The flow field optimization is achieved by adopting the single variable control method to improve the structure of the fan cover, silent components for silence, adjacent structure, and air inlet grille. The corresponding structure optimization scheme is put forward. After optimization, the air quantity for the cooling radiator of the silent type generator unit is 44.33% higher than that of its original structure, and the total cooling air quantity is higher than that of the conventional type generator unit. The research results in this work can provide a theoretical basis for the design of the cooling air flow path of generator units for achieving an optimal cooling performance. [ABSTRACT FROM AUTHOR]

Most of the sprayers used in fruit trees are of the type of jet transported, which use an air flow produced by a fan to transfer the pesticide drop to the tree. In the energy balance of agricultural sprayers assisted by air flow, it is proposed that between 50 and 65% of the power in these equipment is used by the fan that produces the air flow. Air stream sprayers produce high pollution due to high levels of drift. Using the Computer Modeling of Fluids (CFD) the aerodynamics of the air flow is analyzed based on the geometric and kinematic parameters of the fan, which allows to determine the air flow with better characteristics. The selected regimens assess the quality of the plant cover, using image treatment methods. In this case, a work regime is achieved that decreases the amount of power required, maintaining the quality of the treatment. [ABSTRACT FROM AUTHOR]