Search

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]

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]

Coal dust in continuous mining tunnels is extremely hazardous to drivers and other workers. In order to solve this problem, a continuous mining tunnel model is built based on computational fluid dynamics and gas–solid two-phase flow theory. Fluent 19.2 software is used to analyze the effects of air pipe outlet location (d) and external air curtain (EAC) outlet air velocity (vvent) on dust dispersion. The effects on the characteristics of dust dispersion are analyzed separately, and it is concluded that d=7 m is optimal. At this distance, the average dust concentration at the breathing zone height is low, and there is no significant fluctuation or rebound in the dust concentration during the dispersion process. When vvent=6 m/s , the highest dust separation efficiency of 89.3% occurs at a breathing height of y=1.6 m and x=5.82 m (133 mg/m3). The driver's position is protected with a dust separation efficiency of 79.2%. As the vvent value increases, the dust separation efficiency increases slowly. The cost of generating airflow should be considered for dust reduction efficiency, and an optimal vvent of 6 m/s is recommended. The findings of this study can provide a theoretical basis for the selection of ventilation parameters for air curtain dust reduction in continuous mining tunnels with rectangular cross section. [ABSTRACT FROM AUTHOR]

Sludge production increases year by year, which causes great environmental pressure. Low-temperature sludge drying technology is a kind of technology with energy conservation and environmental protection, which is widely favored by the sludge drying industry. The distribution of airflow in the drying chamber is the key factor affecting the drying performance of sludge drying system. In this paper, a uniform flow structure was designed, and a numerical simulation study of the designed flow field in the designed drying chamber was carried out by STAR-CCM+ software. The uniform flow structure of the sludge drying chamber and the optimal flow field distribution conditions on the drying chamber and conveyor belt were obtained so that the uniformity of air distribution in the sludge drying chamber and conveyor belt was improved, and the drying performance of the sludge low-temperature drying system was improved. The effectiveness of the numerical simulation was verified by experiments. The experimental results showed that when the number of shunt plates is three, the shape is an involute arc plate, the distance between the first and third shunt plate is 1,600 mm, and the distance between the second and first shunt plate is 700–900 mm. The flow field distribution on the drying room and the conveyor belt was the most uniform when the inlet wind speed was between 25 and 35 m/s. In addition, there is a strong correlation between the experimental results and the simulation results, which can prove the effectiveness and reliability of the numerical model. The airflow distribution inside the drying room was very uneven: the airflow would change direction with the shape of the obstacle, and the direction of airflow movement was easily affected by the shape of the shunt plates. Therefore, the shape of the shunt plates of the flow sharing structure was different, and the effect of the flow field was also different. Therefore, it was necessary to optimize the distribution uniformity of the flow field in the drying room. STAR-CCM+ software was used to optimize the flow field of the drying room, and the distribution of the velocity field was mainly considered. Through numerical simulation, the shape, quantity, and layout of the flow sharing structure were simulated and optimized, and the flow sharing structure that could improve the uniformity of air distribution in the drying room was designed. As long as these problems are solved, the low-temperature drying system could greatly improve the energy consumption of sludge dewatering, carry out sludge reduction treatment, and also be applied in large-scale industrialization, greatly reducing the problem of sludge treatment and reducing the environmental pollution. [ABSTRACT FROM AUTHOR]

In high-speed gear systems for aeroengines, reducing the fluid dynamic loss, which accounts for the majority of power loss, can significantly improve fuel economy. However, few practical numerical examples are available regarding high-speed gas-liquid two-phase flows involving gear meshing and gear shrouds (gear enclosures, which are effective for loss reduction). Therefore, in this study, the porosity method for object boundaries including the gear meshing, the volume of fluid method, and the surface compression method for the gas-liquid interface was used as fast and numerically stable calculation methods. In addition, a gap was provided at the contact surface of the gear tooth surface to improve the calculation stability, and the oil properties were set considering the difference between the flow resistance in a two-phase flow and that in a single-phase flow (due to the separation of oil particles) to improve the calculation accuracy. To validate the numerical simulation method, a two-axis helical gearbox with a maximum peripheral speed of 100 m/s with specifications equivalent to aeroengine gears was used, and the air flow, oil flow, and fluid dynamic losses were validated. Once the practical accuracy was confirmed, the numerical simulation was used to understand the relationship between air and oil flows, torque, and the effect of the shroud. Consequently, the fluid dynamic loss could be classified phenomenologically. [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]

Knowledge of water and sediment flow characteristics in tunnels is essential for structural safety and post-disaster rescue operations. In this research, we developed a numerical model based on the Euler–Euler approach to simulate the three-phase flow of air, water, and sediment, aiming to predict the spatiotemporal flow characteristics in tunnels following the inrush. The model assumes that air, water, and sediment constitute a continuous medium through each other. The interaction drag between phases was taken into account. A standard k-ε turbulence model was used to simulate the irregular fluid flow. The spatiotemporal fluid behavior within the tunnel was investigated by analyzing the volume fraction, fluid velocity, and fluid pressure. In addition, the effects of the support condition, the machinery obstruction, and the curve radius on the three-phase flow characteristics were discussed. Numerical simulation results indicate that in the spatial dimension, the volume fractions, velocity, and pressure all display gradient distribution; in the temporal dimension, these three parameters all show phased features. Moreover, fluid behavior is greatly influenced by the support condition, the machinery obstruction, and the curve radius. The results establish a fundamental basis for additional investigations concerning spatiotemporal characteristics prediction of water and sediment inrush. [ABSTRACT FROM AUTHOR]

The SARS-CoV-2 (COVID-19) pandemic has highlighted the crucial role of preventive measures in avoiding the spread of disease and understanding the transmission of airborne viruses in indoor spaces. This study focuses on a novel personal protective equipment consisting of a fan-peaked cap that creates a jet flow of air in front of the individual's face to reduce the concentration of airborne viruses and decrease the risk of infection transmission. Direct numerical simulation is used to analyze the effectiveness of the device under certain conditions, such as the velocity of the airflow, flow orientation, ambient conditions, and geometrical factors. [ABSTRACT FROM AUTHOR]

The deformation process of compound droplets moving in air flow was studied by using volume of fluid model. In this paper, the kinetic process of air-in-liquid CeO2 compound droplets in air flow is reported by numerical simulation. First, the effects of initial velocity, initial diameter, and internal and external pressure difference on droplet behavior were studied when the compound droplets finally reached the morpho-steady state. The self-compiled program is used to process and analyze the digital image of the simulated broken image. The results show that, under the action of four main forces, namely, external aerodynamic force, internal pressure, viscous force, and surface tension, the inner surface of the hollow droplets gradually begins to break and continues to expand to the outer surface to break. With the increase in the pressure difference between inside and outside of the hollow drops, the pores are severely deformed and cracked. The increase in velocity leads to the imbalance of internal and external surface forces caused by the increase in aerodynamic fluctuation on the outer surface of hollow droplets. With the decrease in the diameter of the hollow droplet, the pressure threshold of the droplet breaking decreases and it is easier to break. [ABSTRACT FROM AUTHOR]

In this study, a novel air blower by applying the DBD plasma actuator for a PEM fuel cell is proposed for reducing power consumption and air flow saving. For this purpose, the DBD plasma actuators are installed on the bottom surface of the cathode channel of a PEMFC. The impact of the application of DBD plasma and the number of DBDs on the air mass flow rate and performance of PEMFC were numerically investigated. Results show that in comparison to the conventional air blower model, using the DBD plasma air blower at the cathode channel of a PEMFC results in a reduction of velocity magnitude and uniform velocity distribution of airflow within the cathode channel. Also, results indicate that the DBD plasma air blower model with less air flow consumption provides almost the same current density and performance as the conventional model. Results illustrate that the DBD plasma air blower with 3 DBDs can be a suitable candidate to obtain the best design for the DBD plasma air blower. The robust advantages of using the DBD plasma air blower become more underscored when the findings present the 90.31% reduction in the average power consumption. • DBD actuator as air blower for a PEM fuel cell is numerically investigated. • Using DBD actuator air blower PEMFC significantly decreased air consumption. • Using DBD actuator air blower decreased the 90.31% average power consumption. [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]

Accurate and high‐resolution numerical simulations are crucial for preventing manufacturing defects during polymer injection molding. However, achieving efficient and precise simulations in this field remains a subject of ongoing research. In this study, we develop a macro‐scale numerical model to describe the behavior of melted polymer during the filling phase. Employing our in‐house finite‐element solver, XNS, we simulate the polymer and air flows as a two‐phase flow using the level‐set method. This formulation involves significant discontinuities across the interface, therefore a high mesh resolution along the interface becomes necessary. Furthermore, to accurately capture the polymer behavior along the wall, we apply a variable Navier slip condition that is dependent on the mesh size. To assess the impact of mesh size on the solution, we compare the results obtained with different levels of mesh refinement. Additionally, we investigate the effects of localized mesh refinement at the wall boundary and conclude that refinement in the interior of the channel is also required. Through our analysis, we highlight the importance of high‐resolution meshing and appropriate wall boundary conditions in achieving accurate simulations of polymer injection molding. This research contributes to the ongoing efforts in improving the understanding of the complex phenomena involved in this manufacturing process. [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]

The strong flow field in a hoistway will cause a significant piston effect during the operation of high-speed/ultra-high-speed elevator. Thus, studying the airflow in the hoistway and the reasonable opening of ventilation holes is important. First, a three-dimensional geometric model of the ventilation holes (VHs) and elevator car was established. Based on this model, a multi-region dynamic layering method was proposed. The movement of the unsteady airflow in hoistways with different numbers of VHs and the interaction between the VHs were then analyzed. The correctness of the numerical simulation method was verified by comparing the results of the simulation, experiments and theoretical calculations. Finally, the influence of the number, location and cross-sectional area of the VHs on the airflow movement was analyzed, and the optimal opening positions of one and two pairs of VHs were discussed. The results showed that the variations of the number, location and cross-sectional area of the VHs had a significant influence on the airflow movement. According to the quantitative analysis of the ventilation efficiency, the optimal positions of one and two pairs of VHs were located in the middle of the hoistway and the upper and lower sides of the middle position, respectively. [ABSTRACT FROM AUTHOR]

Multi-parameter study on the subsonic equilibrium air plasma flows in the cylindrical discharge channel of an induction RF-plasmatron IPG-3 with the maximum operating power of 1 MW is presented. Simulations are carried out by numerical solution of full Navier–Stokes equations coupled with a two-dimensional equation for high-frequency electric field; the discretization of the equations is performed on a staggered Cartesian mesh. An effective method for calculation of the transport coefficients for ionized multi-component air (including the plasma conductivity) in the temperature range 300–15000 K is applied, with the higher-order approximations by the Sonine polynomial in the Chapman–Enskog method. Simulation results are presented, including the flow fields, electric field, and thermodynamic parameters of the air plasma in the discharge channel of a high-power induction plasmatron. The results obtained reveal for the first time the structure and parameters of a plasma torch in a large-diameter (200 mm) discharge channel at powers up to 300 kW, providing the axial specific enthalpies at the channel outlet as high as 68 MJ/kg. [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 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 aim of the work is to describe the air flow in an enclosed space, which is ventilated by a diffuser, to select an appropriate turbulence model, to solve the problem using the ANSYS Fluent, to study the effect of heat sources in a room on air flow under various conditions and to simulate the movement of particulate matter. As a result, the distribution of PM2.5 particles in the room was shown, which enter the room through the diffuser. According to the data obtained, the temperature value increases with an increase in the area of the heat source, that is, with an increase in the number of batteries. The maximum temperature corresponds to a room with a warm floor, the minimum temperature is observed in a room with one battery. The obtained numerical data can be used when installing ventilation or heating devices inside buildings, when simulating the movement of harmful particles in the air, when determining the optimal ways to clean the air. [ABSTRACT FROM AUTHOR]

In the present analysis, three potential serpentine flow channel designs for a flat-sheet membrane-based dehumidifier are designed and evaluated in terms of performance metrics such as dehumidification rate (DR), approach temperature (AT), pressure drop (ΔP), and coefficient of performance (COP). The dry side inlet air temperature and relative humidity (RH) are set at 27°C and 0%, and the wet side inlet air temperature and RH are fixed at 40°C and 85%. The inlet air flow rates of the dry and wet sides are both controlled in the range of 20-60 L min−1. The simulation results revealed that the geometrical design of the flow channels has a remarkable impact on the dehumidification performance of the dehumidifier. It is outlined that the water vapor concentration and temperature distribution at the outlet of all proposed serpentine flow channels are almost identical, showing the oversized design of the three- and six-inlet serpentine channels. Under the air flow rates of 30 ∼ 60 L min−1, it is seen that the DR, AT, and ΔP of three-, six-, and nine-inlet serpentine channels are in descending order. It is found that the size and quantity of the channel outlets and inlets have a great influence on the pressure drop. Moreover, the dehumidifier with nine-inlet serpentine flow channel can provide the highest COP with a limited increase in the pressure loss. Hence, this channel design can be a good candidate to be implemented in the flat-sheet membrane-based dehumidifier. The findings of this study could be beneficial for the design of novel dehumidifiers. [ABSTRACT FROM AUTHOR]

The measurement and estimation of pressure drop through porous beds are important in the design and development of grain drying and aeration systems. Three inlet interconnected channels were designed and developed as inlet duct floors of an experimental grain silo. The channels were formed into shapes resembling the characters E, F and H. The pressure drop and air distribution were evaluated at different airflow rates for use as a small scale on-farm grain silo. It was observed that the pressure drop increased with the airflow rate and the height of the rough rice in the storage bin. Duct configuration of F and H represents the maximum and minimum values for pressure drop, respectively. The pressure at different heights inside the bed was uniform for all three air inlet duct configurations. Hukill & Ives and Ergun equations were used to fit with experimental data. The modified constant coefficients of both equations were determined for each of the three configurations. The Ergun equation fitted best the experimental data for the entire airflows range. Using the modified Ergun equation, a numerical simulation of the flow inside the rough rice bed was performed in the COMSOL Multiphysics software v6.1 and the velocity distribution inside the bed was presented. The simulated results revealed that the bin with H inlet duct configuration has better performance in continuous aeration process compared to E and F configurations, whereas an F duct configuration has better air penetration ability at the bottom and near the centre of the bin. [Display omitted] • Pressure drop through rough rice measured experimentally for three inlet duct configurations. • Coefficients of Ergun's equation for pressure drop modified for three inlet duct configurations. • Highest and lowest pressure drop values observed for F and H configuration, respectively. • F-duct configuration design recommended for an immediate aeration process. • H and E duct configurations are suitable for a continuous aeration process. [ABSTRACT FROM AUTHOR]

To better analyze the distribution law of airflow in the wind sieve type cleaning device, this study took the cleaning device of Yafeng 4YZL-6S corn seed harvester as an example and conducted numerical simulation and comparative analysis of the airflow field inside the cleaning device under the sieve plate opening scales of 12, 16 and 20 mm using CFD software. The numerical simulation showed that the distribution of airflow velocity above the sieve surface was uniform at a sieve plate opening scale of 16 mm. Airflow velocity measurements were performed on the test prototype using an anemometer to verify the accuracy of the numerical simulation results. The simulation test results were supplemented by field trials, which showed that when the speed of the cleaning fan was 1200 r/min and the sieve plate opening scale was 16 mm, the impurity rate in the field harvest of the operating machinery was 1.03% and the loss rate was 1.91%. The operating effect met the standard of mechanized corn grain harvesting. This paper can provide a reference for the design and working mechanism research of corn seed harvester cleaning devices. [ABSTRACT FROM AUTHOR]

Determining the behavior of aerosol drug particles is of vital importance in the treatment of respiratory tract diseases. Despite the development of imaging techniques in the pulmonary region in recent years, current imaging techniques are insufficient to detect particle deposition. Computational fluid dynamics (CFD) methods can fill the gap in this field as they take into account the very different physical processes that occur during aerosol transport. This study aims to numerically investigate the airflow and the aerosol particle dynamics on a realistic human respiratory tract model during multiple breathing cycles. The simulations were conducted on the different breathing conditions for people under light, normal, and heavy physical activities, and the aerosol particles with different aerodynamic diameters (i.e., dp=2, 5, and 7 µm). The numerical results were validated by comparing extensively with experimental and numerical results. The results indicated that the airflow during inspiration and expiration was characteristically different from each other and changed with the inspiration flow rate. It was determined that small-sized particles followed the streamlines and moved towards the distal of the lung under low respiratory conditions. On the other hand, larger particles tended to deposit in higher generations due to the higher inertia. It was found that with the increase of inspiration flow rate the deposition of particles increased for all particles during multiple breaths. For light breathing conditions, low deposition efficiencies were obtained because the particles followed the streamlines and moved towards the distal part of the lung. The particle deposition efficiency under heavy breathing conditions was 28.2% for 2 µm, 33.05% for 5 µm, and 38.4% for 7 µm particles. The results showed that inertial impaction plays an active role in particle deposition. [ABSTRACT FROM AUTHOR]

The study focuses on modelling a cold, confined and swirling airflow in a magnesium burner. Direct observations of the magnesium combustion in the combustion chamber proved the existence of a significant recirculation zone in the burner. Before modelling the high flame temperature and the turbulent mixture of solid fuel and products in this burner, the correct simulation of a high swirl cold flow and the creation of a recirculation zone is a crucial first step. Experimental measurements were made placing a hot-wire anemometry at different positions in a PMMA replica of the burner, to validate the simulation results returned by the Fluent software. In a low swirl case (S=0.13), simulations performed using different eddy viscosity models were compared and the standard k- ɛ model was proved to more accurately predict the velocity profiles and the central recirculation zone. In a high swirl case (S=2.94), the turbulence and its anisotropy were too strong and the RSM model was proved to more accurately predict the position, size and shape of the central toroidal recirculation zone. Important errors were still observed for the velocity values. Higher discretization orders (second- or higher-order) could not be used in this case, due to induced numerical instabilities. • A cold, confined and swirling airflow in a magnesium burner is modelled. • Velocity measurements were performed in a PMMA replica of the combustion chamber. • In a low swirl case, the RNG k- ɛ model gave better simulations. • In a high swirl case, the RSM model predicted the central toroidal recirculation zone. [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]

In order to improve the performance of an air turbine starter，the aerodynamic performance and flow field details of the air turbine starter are studied by combining numerical simulation and experiment. The numerical simulation results show that there is obvious flow separation inside the inlet elbow，leading to poor uniformity of the downstream flow field. There is a certain boundary layer separation on the surface of the guide vane and rotor blade，and the flow field is relatively poor because the smooth flow is not fully considered in the exhaust frame. The comparison between the numerical simulation results and the experimental results shows that the air flow rate obtained by numerical simulation is about 1.90% lower than that of the experiment，and the turbine power is about 1.04% higher. Generally speaking，the numerical simulation is in good agreement with the experiment，and this numerical simulation method has a high accuracy to study the air turbine starter. The performance of the air turbine is significantly improved by the optimized design of the guide vane. The power of the air turbine is increased by 14.2% compared with the prototype. [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]

The high-pressure capture wing (HCW) configuration has excellent aerodynamic characteristics verified by theoretical, experimental, and numerical simulation methods. It has a good effect on improving vehicle lift at hypersonic speed. A HCW-V configuration based on the HCW was proposed in this paper. This configuration further increased the vehicle's lift by increasing the wedge angle of the capture wing and forming a compression plane on the lower surface. We obtained the pressure ratio relationship between the upper and lower surfaces of the HCW-V configuration concerning the free-stream airflow Mach number, the body compression angle, and the captive wing wedge angle based on theoretical derivation. It was nearly 60% higher than the HCW configuration pressure ratio. In addition, the influence of the HCW-V configuration on the vehicle's aerodynamic characteristics at different Mach numbers and body compression angles was studied through numerical simulation methods. The HCW-V configuration improved the lift-to-drag ratio by at least 25% compared with the HCW configuration. The expression of the lift coefficient of the vehicle CL = −0.095Ma∞tanδ + 2.352tanδ + 0.031θ + 0.010 under the model presented was obtained in this study. Meanwhile, the adaptability of this configuration to varied Mach number and attack angle was investigated further. The average lift-to-drag ratio of HCW-V was increased by 23.7% and 7.09% at varying Mach numbers and angles of attack. The lift-to-drag ratio of the three-dimensional HCW-V configuration is 14% higher than that of the HCW configuration when the wedge angle is 4.19°. [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]

Signal noise is a crucial factor connecting instrument design and analytical performance in ICP-MS. The audio-frequency (a.f.) noise observed in the signal noise power spectra is caused by the turbulent mixing of entrained air with the plasma flow. In this paper, we proposed a COMSOL®-based numerical method for predicting the fundamental parameters of an analytical ICP source. The proposed method was verified by comparing the fundamental parameters simulated in this work with the experimental/simulation values from the literature. In a custom-built ICP source, we observed ion clouds originating from individual rare-earth-element powder and also investigated the characteristics of gas flow pulsation using a high-speed camera. The simulated velocity downstream of the torch exit agrees with the experimentally determined velocity, demonstrating the reliability of the proposed numerical method. By retrieving the maximum value and the half-width at half maximum in the simulated profile of gas velocity at the torch outlet in the absence of an interface, the pulsation frequency could be predicted accurately using an empirical formula. The effects of torch geometry, sample type and operating parameters on the pulsation frequency were evaluated. The dependence of the pulsation frequency on the sampling depth was investigated in the presence of an interface. The experimental data reported in the literature should be attributed to a coupling effect of vortex dissipations in the longitudinal and lateral directions. Finally, the suppression mechanism of using a bonnet on the a.f. noise was explored by comparing the flow fields without and with a bonnet. Introducing a bonnet or an extension makes the entrainment position move away from the analytical zone and reduces the fluctuation intensity, eliminating the a.f. noise. The work presented in this paper is beneficial for ICP-MS instrument optimization, analytical performance improvement and data interpretation. [ABSTRACT FROM AUTHOR]

Dust storms, resulting from aeolian erosion, pose significant environmental hazards, while farmland is one of the main sources of dust storm release. An effective strategy to mitigate surface wind speed and curb dust emissions involves the establishment of windbreaks on the periphery of oasis farmland. This study conducts a series of numerical simulations using computational fluid dynamics (CFD) to explore the airflow fields around windbreaks with diverse systematic structural parameters, encompassing porosity, planting spacing, and fence effects. The main findings are as follows: (1) When the vegetation porosity is consistent (e.g., porosity α = 0.7, 0.8, and 0.9), exact geometry results can effectively reflect the distribution of wall shear stress, while the porous medium model overlooks these details. (2) The "Venturi effect" contributes to the acceleration of surface erosion and improper planting spacing results in an elevation of near-surface velocity. Planting spacing of 0.5 m demonstrates superior wind speed reduction performance, mitigating aeolian erosion and accumulation. (3) When the fence is positioned at l = 5 h (h represents the height of the windbreaks), the flow field around the windbreaks is minimally influenced. The optimal placement distance for fences should be close to the windbreaks, featuring minimal porosity (l = 0 h , α = 0.1), extending the shelter distance from 3 to 4 h to 5–6 h. The research results can provide a theoretical basis for optimizing the plant configuration of biological desertification control and soil erosion control measures. • The exact geometric model of windbreak reflects more details of the three-dimensional flow field. • There is an optimal value between the planting spacing of the windbreak and the venturi effect. • The planting spacing of 0.5 m has better wind speed reduction performance. • The optimal arrangement of the fence should be tightly close to the windbreaks. [ABSTRACT FROM AUTHOR]

Attic geometry and ventilation in a different attic geometry play a very important role in residential building energy performance. To evaluate the effect of ventilation ratio and vent balance on attic performance, a two‐dimensional finite volume model is employed to simulate the buoyancy‐driven turbulent ventilation and heat transfer in an attic space of different geometries like gable, gambrel, and saltbox roofs of residential buildings under winter conditions. The impact of ventilation ratio on ventilating airflow rate, heating load rate, and rate of heat gained is investigated for all three types of roof geometries. The model under consideration consists of a passive ventilation system with a ridge and soffit vent. Meshing is done by using ANSYS Workbench and numerical simulations are carried out by using ANSYS FLUENT 19 analysis software. The effect of passive ventilation on ridge‐vent attic performance is evaluated in this study. Ventilation ratios for soffit vents ranging from 1/400 to 1/25 are investigated. Convection boundary conditions are used for the attic walls to account for thermal resistances of ceilings and roofs. In addition, the performance of these vented attics is compared to the heat transfer in a sealed attic. The results show that the symmetrical airflow pattern exists in a vented attic, in contrast to the asymmetrical airflow patterns found in a sealed attic. From the study, it is evident that an increase in ventilation ratio reduces attic heating load irrespective of the increase in ventilation airflow rate. The rate of airflow increases with an increase in ventilation ratio in all three types of roof geometries that is gable, gambrel, and saltbox roofs. In the case of gable roof configuration, increasing the ventilation ratio from 1/200 to 1/100 results in an increase in ventilating mass flow of 75%, while an increase of ventilation ratio from 1/50 to 1/25 only increases the ventilating mass flow by 40%. In the case of gable roofs increasing ventilation ratio from 1/200 to 1/100 results in a 20% decrease in attic heating, whereas an increase in ventilation ratio from 1/50 to 1/25 results in a 10% decrease in attic heating. [ABSTRACT FROM AUTHOR]

Construction ventilation runs through the entire construction process of large underground caverns and is the key to ensuring construction progress and project safety. For the specific underground cavern group of pumped-storage power plants, a three-dimensional model is constructed, and the CFD method based on fluid mechanics theory is used to simulate the ventilation flow field of the underground cavern group. Through the comparison of the airflow in the main caverns and the air velocity distribution law, Quantitative analysis of the influence of the diameter of the ventilation shaft and the inclination of the shaft on the ventilation flow field shows that when the diameter of the ventilation shaft is 8 m and the inclination of the shaft is 80°, the ventilation effect in the underground cavern group is the best. Applying this scheme to engineering practice and conducting on-site tests, the average relative error of the measuring points is 11.32% by comparing the measured data and the simulation results, which verifies the correctness of the CFD method used. It provides reference value for studying the construction ventilation of underground caverns. [ABSTRACT FROM AUTHOR]

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]

In this paper, three types of wire-plate electrostatic precipitators with expanded-shrunk spoilers (ESP-ESSs) were proposed. The influences of different geometric characteristics and arrangements of the expanded-shrunk spoilers (ESSs) on the electric field intensity, airflow field, particle trajectory, and collection efficiency were investigated by experiment and numerical simulation. The ESP-ESSs was compared with ESP with parallel plates (ESP-PP). The numerical results were relatively in agreement with the experimental data. The maximum error was 6.5%. The results showed that with the increase of the ESS height, the electric field intensity increased. The ESSs could generate low-velocity vortices contributing to extend the retention time of particles, which was conducive to particle collection. In general, the collection efficiency of the ESP-ESS was superior to the ESP-PP, but there was no advantage for fine particles at high inlet gas velocity and low applied voltage. [Display omitted] • The performances of three different ESP-ESSs were investigated. • The ESP-ESSs were systematically compared with ESP-PP. • The effects of ESSs on performances were studied. • The mechanism of the ESS enhancement was analyzed [ABSTRACT FROM AUTHOR]

The turbulent airflow generated by the shearer's rotation has a significant impact on the spread of cutting dust. In this study, the actual shearer drum was used as a physical model, and the MRF method was applied to simulate coal cutting operations with consideration of rotating fluid, accurately reproducing the turbulent airflow generated during cutting. By comparing the different simulation results, it is found that: the wind flow under systematic ventilation is gentle and even, while the cut-off wind flow generated by "inlet" has a great impact on the coal mining area in terms of scope and degree, and the horizontal and vertical dispersion is very strong, with a large amount of wind flow shifting in the range of 17 m < x < 36 m, and the dust mass concentration increasing rapidly; When the MRF method is adopted, the wind flow disperses more gently, and the dust is shifted to the pavement within the ranges of 19 m < x < 25 m and 27 m < x < 36 m, which makes the dust distribution more uniform and continuous in space, and forms a dust belt with high concentration of about 10 m in length on the downwind side of the front drum, which is more in line with the production reality. • First application of MRF method in fully mechanized mining face. • Studied the dynamic drum cutting law of fully mechanized mining face. • Constructed a 1:1 drum model according to the actual production. • Obtained the motion characteristics of dust under dynamic simulation. [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]

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]

A rotary dust collector that operates on the principle of a centrifugal separator has been developed. A feature of its design is the presence of a bypass recirculation channel of purified air with a flow regulator, two outlet pipes with flow unswirlers in the form of spiral channels. The calculation of the motion of dust particles with a density of 3000 kg/m3 and a diameter from 1 to 100 μm has been performed. Research has been carried out to improve the efficiency of the apparatus using a central compositional plan and to establish rational design and operation parameters of the mixer of recirculation air and air being purified. [ABSTRACT FROM AUTHOR]