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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]

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]

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 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]

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]

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]

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]

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]

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]

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]

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]

This paper describes a numerical simulation of vibrations of an elastic rod whose height is significantly greater than its transverse dimension and which is placed perpendicularly to the external flow and rigidly mounted on a substrate. Simulation is carried out in the ANSYS software package using bidirectional coupling technology. The natural frequencies and vibration modes of the rod are calculated. The airflow structure is analyzed and its features in the vicinity of the model are described. The process of exciting the vibrations of an elastic rod under the action of an external flow is investigated and its stress-strain state is determined. Vibration modes in the direction of an incident flow and in the transverse direction are determined. It is shown that, if the first natural frequency and the vortex shedding frequency reach close values, the amplitude of the rod vibrations in the transverse direction sharply increases to a value approximately equal to 0.06 of the rod height, which is followed by natural vibrations with a constant amplitude in the transverse direction and variable amplitude in the direction of the incident flow. [ABSTRACT FROM AUTHOR]

The freshwater table is the upper boundary of the entire freshwater lens and is very important for understanding the formation of freshwater lenses and for managing fresh groundwater on islands. However, little attention has been given to the position of the freshwater table, as it is difficult to visually distinguish it from the unsaturated zone in physical models. Under the natural conditions, the process of rainfall infiltration into soils involves both pore-water flow and air flow in soil voids, and thus, the airflow induced by infiltration has implications for groundwater recharge and formation of freshwater lenses. Therefore, research on the precipitation-fed freshwater table in an oceanic island should consider the water-air two-phase flow induced by rainwater infiltration. This study focuses on simulating the steady-state position of the freshwater table using TOUGH2/EOS7, a model that considers liquid and gas two-phase flow and brine, water and air three-component in unsaturated-saturated porous media, and verifying it by comparing the numerical results with the analytical solutions. The numerical results delineated the entire geometry of island freshwater lenses that involve a freshwater table replenished by precipitation, which were then compared with the Dupuit-Ghyben-Herzberg (DGH) analytical solutions that ignore the outflow face and with Van der Veer's analytical solutions that consider the outflow face. Reasonable fits between the numerical results and the DGH analytical solutions were obtained, with the exception that the lens obtained by the DGH analytical model is smaller in size than that simulated by the numerical model for various cases; a better agreement was found between the results from the numerical model and Van der Veer's analytical solutions for the homogeneous island case. The agreements between the results from the proposed numerical model and the DGH and Van der Veer's analytical models verified the proposed numerical model. The numerical modeling method investigated here enhanced the numerical simulation techniques for studying groundwater movements and the interaction of freshwater and saltwater on oceanic islands and can provide a reference for modeling more complicated island groundwater patterns. [Display omitted] • The steady-state position of the freshwater table of island was numerically modeled. • A numerical model that considers both the pore-water and air flow was established. • Reasonable fits between the numerical results and the DGH analytical solutions were obtained. • A better agreement was found between the numerical results and Van der Veer's analytical solutions. [ABSTRACT FROM AUTHOR]

In tropical countries, part of the horticultural production is carried out in hillside soils. In recent years, due to the adverse effects of climate change and other biotic factors that limit and affect agricultural production, the use of roof structures has been promoted as a technological means to improve production in this type of production system. The microclimate study of structures built on slopes is scarce, therefore farmers continue to build the same type of structure without technical design criteria and without knowing if the microclimate conditions generated are suitable for the crops. In the present research work, an experimentally validated 3D CFD numerical model was implemented to analyze air flows and spatial temperature behavior in a roof structure built on a site with broken topography. The results obtained allowed us to find out that the air flows are strongly affected by the longitudinal and transversal slopes of the land, which produces low ventilation rates that generate thermal gradients above 8 °C and highly heterogeneous thermal behavior, factors that are not suitable for horticultural production. [ABSTRACT FROM AUTHOR]

Clouds have an important impact on Earth's energetic balance, so measuring accurately the microphysical parameters and using them in research has become one important step in atmospheric studies. Regarding the fact that light scattering probes convert the flow rate to concentration, any wrong assumption or measurement of the flow rate can lead to incorrect results. Applying numerical simulation to an airborne cloud microphysics measurements instrument can provide information that can be measured in any point of the sampling volume, and further used in determination of microphysics parameters, providing more accurate data. Taking this into consideration, in this paper are presented the results of numerical simulation applied to Cloud Aerosol and Precipitation Spectrometer and the comparison with results reported in literature. [ABSTRACT FROM AUTHOR]

The biomass is one of the promising energy sources of the future. It is possible to use its energy potential through thermo-chemical conversion processes of pyrolysis and gasification. A particular attention has been recently paid to biomass gasification. Several models have been advanced to describe this complex process. The present communication suggests a flowsheet simulating a wood biomass gasifier. The simulations are carried out by ASPEN PLUS V.8.0 commercial software. The thermo-chemical models assume that the reactants reach a chemical equilibrium. The flowsheet includes three stages: raw biomass drying, a gasification process and a products separation. The simulations provide to predict the final composition of the gas mixture produced by biomass gasification. Sensitivity analyses are performed to determine the effect of the pressure, the air flow, the moisture content, and the air stream enthalpy on the amounts of the gases produced. [ABSTRACT FROM AUTHOR]

Dust seriously affects the safe production of coal mines, and a high dust concentration operating environment is harmful to the health of miners. It is necessary to take dust reduction measures on the working surface. In order to improve the effect of dust prevention and control on a fully mechanized excavation face, we studied the characteristics of dust production in a fully mechanized excavation face and the working principle of inside inhaling and outside pressing dust collectors, selected three shapes of dust collector trumpets, and used the FLUENT software to carry out the numerical simulation of air flow and dust concentration. By analyzing the state of movement of air flow and the concentration change in discrete phase dust particles through simulation, the results showed that the C-shaped bell mouth had the best effect on reducing the concentration of dust on the working surface and can effectively improve the working environment of a fully mechanized excavation face, which provides theoretical guidance for the prevention and control of dust in fully mechanized excavation work. [ABSTRACT FROM AUTHOR]

Cell exposure experiments at the air-liquid interface (ALI) are used increasingly as indicators for health effects and for the impact of aerosols on the lung. Thereby the aerosol particles are kept airborne and can deposit on a cell surface area similar to the human respiratory tract (RT). However, geometry and air flow rates of an ALI system deviate considerably from the RT. As the tissue-delivered particle dose to the lungs (TD) can hardly be measured, computer models of particle deposition are used here to mimic both the particle deposition at ALI and in the RT. An ALI exposure setup (VitroCell GmbH) for an airflow rate of 100 cm3 min−1 is selected, where the particle deposition model has been verified experimentally. For the RT we use the hygroscopic lung deposition model of Ferron et al. (2013). Model runs are performed for the particle deposition and for the deposited particles per surface area in both the ALI and the RT. The results show that the ALI-deposited mass is 1-2 orders of magnitude higher than in the alveolar region, because the surface area of the lung region is substantially larger. A particle size range from 40 to 450 nm is identified, where the ratio of both the deposition in a lung region and the deposition at the ALI varies by a factor less than two. Mean values for this ratio are 31 and 101 for the tracheo-bronchial and the alveolar region, respectively. The same size range is found for the ratio of the deposited particles per surface area in a lung region and at the ALI. For this range the mean surface deposition at the ALI is 23- and 1575-times larger than in the tracheo-bronchial and the alveolar lung region, respectively. The effect is partly compensated by different flow rate and cell size. Copyright © 2020 American Association for Aerosol Research [ABSTRACT FROM AUTHOR]

• Wind towers incorporated to a greenhouse to provide wind driven natural ventilation. • Natural ventilation performance of the wind towers was assessed by CFD simulations. • CFD model was validated by flow visualization, point measurement, and PIV measurement. • At a wind speed of 3 m/s, the wind towers provided the recommended air change rate. • At a wind speed of 3 m/s, air velocity at crop height was within recommended values. In this study, the air change rate and airflow distribution inside a greenhouse equipped with wind towers were analyzed using Computational Fluid Dynamics (CFD) simulations, considering different wind speeds (1–5 m/s) and incident angles (0–45°). The validation methods included smoke visualization, hot wire velocity point measurements, and Particle Image Velocimetry (PIV) measurements. The visualized and simulated flow regimes exhibited fair agreement. The average discrepancy between the hot wire velocity point measurements and simulated results was about 7.96%. The predicted vector fields in the inlet and outlet wind towers demonstrated good qualitative agreement with the corresponding PIV measurements. The discrepancy between the predicted and measured maximum air velocity in the inlet tower was 15%, while it was 3% in the outlet wind tower. At an external wind speed of 3 m/s and normal incidence angle, the average velocity of the airflow entering the greenhouse was 0.65 m/s (about one air change per minute), while the average air velocity in the greenhouse was 0.44 m/s. The average air velocity inside the greenhouse at a crop height (1 m) ranged from 0.3 to 1.8 m/s, which is within the optimum range of recommended air velocities for greenhouses. [ABSTRACT FROM AUTHOR]

This paper investigated the cooling performance of a high-efficiency dew-point evaporative cooler with optimised air and water flow arrangement using the combined experimental and numerical simulation method. The experimental results showed that the wet-bulb efficiency of the dew-point evaporative cooler was increased by 29.3% and COP was increased by 34.6%, compared to the existing commercial dew point air cooler of the same capacity. An improved two-dimensional, multi-factor engaged numerical model which can scale up and optimize the size and capacity of the cooler was developed. The numerical predictions agreed well with the experimental results, indicating that the cooling rate of the dew-point evaporative cooler is influenced by the dew-point evaporative cooler structure. The cooling efficiency of the dew-point evaporative cooler with corrugated plates is more than 10% higher than with flat plates and the cooling efficiency of the dew-point evaporative cooler with the actual flow arrangement is only 62%–67% that of a dew-point evaporative cooler with an ideal counter-flow arrangement. The cooling efficiency can be improved by increasing the channel length and the air entrance length, and decreasing the channel width and channel gap within a reasonable range. [ABSTRACT FROM AUTHOR]

Row-based cooling has been recommended for cooling scenarios with high power densities. Existing studies on row-based cooling have mostly focused on good results, and the effectiveness and limitations of it need to be evaluated to optimize it. In this study, some airflow problems were observed by a field experiment for a data center with row-based cooling. Subsequently, a simulation corresponding to this data center was performed to fully learn and verify some airflow conditions below those expected, such as hot spots in some racks and vortex airflow, where the Supply Heat Index of modules 1 and 2 are 0.37 and 0.31. To further determine the airflow characteristics of row-based cooling, a comparative simulation of airflow distribution of row-based cooling and raised-floor cooling was performed. Finally, the effectiveness and limitations of row-based cooling were presented. The results showed that row-based cooling only decreases the Return Temperature Index by 0.4%. The limitations of it include vortex airflow, hot spots in head racks and adjacent racks of in-row coolers, and interaction between different modules; they are easy to occur in row-based cooling and some improvement suggestions are presented in future work. [ABSTRACT FROM AUTHOR]

The air-breathing pulsed detonation thrust module (TM) for an aircraft designed for a subsonic flight at a speed of up to 120 m/s when operating on a standard aviation kerosene was developed using the analytical estimates and parametric multivariant three-dimensional (3D) calculations. The TM consists of an air intake with a check valve, a fuel supply system, a prechamber-jet ignition system and a combustion chamber with an attached detonation tube. An experimental sample of TM was fabricated, and its firing tests were carried out on a test rig with a thrust-measuring table. In firing tests, TM characteristics are obtained in the form of dependencies of effective thrust, aerodynamic drag and fuel-based specific impulse on fuel consumption at different speeds of the approaching air flow. It has been experimentally shown that the fuel-based specific impulse of the TM reaches 1000-1200 s, and the effective thrust developed by it reaches 180–200 N. [ABSTRACT FROM AUTHOR]

By considering the parametric variation of an individual boron particle in a boron agglomerate, the heat transfer, and the mass transfer between the boron particle agglomerate and the surroundings, an ignition and combustion model of a boron agglomerate is proposed. An experiment of a ramjet combustor using a boron-based slurry fuel is designed and operated for the purpose of validating the ramjet configuration and verifying the combustion of boron particles. Then a mathematical model for simulating a multiphase reacting flow within the combustor of a boron-based slurry fuel ramjet is established. Kerosene droplets and boron particles are injected discretely to the burner flowfield, and their trajectories are traced using the discrete phase model. The influence of the agglomerate size, bypass air mass flow rate, initial boron particle diameter, and boron particle content on the combustion efficiency of the slurry fuels is analyzed in detail. The results show that the combustion efficiency decreases with an increase in the agglomerate radius, initial boron particle diameter, and boron particle content. The combustion efficiency increases with an increase in the mass flow rate of bypass air. If the agglomerate diameter is greater than 100 μm or the bypass air mass flow rate is smaller than 50 g/s, the boron particles cannot be fully burned. [ABSTRACT FROM AUTHOR]

In this paper, a solution method for the temperature distribution of rectangular test specimen with a high-speed heat air-flow passing through is proposed based on the heat transfer theory and numerical calculation, and the feasibility of temperature prediction method is validated. Firstly, the partial differential equations to describe the average temperature in the section of the hot air-flow and the specimen are established and the solving method using MATLAB solver is proposed. Then, based on heat transfer conduction equation and the average temperature, the temperature distribution at different point in each section is calculated. The comparison between numerical computation and experiment shows that two results are in good agreement, which verifies the correctness of the presented prediction method of the temperature distribution of the specimen. [ABSTRACT FROM AUTHOR]

Abstract In the frame of the development of the equatorial outboard blanket module of the EU DEMO (Demonstration Fusion Power Plant) blanket concepts, the qualification and testing of mock-ups are foreseen by means of different experiments to validate models and computer codes for the simulation of abnormal and accidental operations. In this context, a functional test mock-up of the first wall (FWMU) is planned to be integrated in the HELOKA facility (HElium LOop KArlsruhe) at KIT in order to investigate typical safety relevant transients such as a LOFA (Loss Of Flow Accident). This work is aimed at the development and validation of a detailed thermal-hydraulic model of the FWMU plate by means of the system code RELAP5-3D. To this purpose, a comparison with CFX analyses for both steady-state and transient conditions has been performed as well as a calibration with the pressure loss characteristics experimentally determined under air flow conditions. The present model will be integrated into the completed HELOKA loop model to simulate different operational scenarios, but also to support the definition of a suitable text matrix, set-up the control and to define the instrumentation needed for the experiment. [ABSTRACT FROM AUTHOR]

Abstract Slope drainage is crucial to landslide mitigation, yet current drainage technologies still encounter difficulties in achieving fast drainage. Based on the permeability characteristics of unsaturated soil with low water content, this study presents a new drainage measure, known as the air injection method, by injecting compressed air into the soil to form a low-permeability unsaturated zone for slope drainage. A series of physical model tests and numerical simulations are performed to study the formation process of the unsaturated zone by the air injection method. The study shows that the formation process undergoes four phases according to the variations in groundwater level in the slope and the features of the air–water flow in the unsaturated zone at different injection pressures. Additionally, numerical analyses indicate that the two-phase flow in the development of the unsaturated zone gradually transitions from a water-flow- to an air-flow-dominant zone. Furthermore, the expansion of the unsaturated zone by air injection is asymmetrical along the injection point, but tends to align with the downstream slope direction owing to the influence of groundwater flow. The findings are important for the establishment of the theoretical foundation of the air injection method, and the optimization of the air injection scheme. The proposed method and results obtained through laboratory investigation and numerical simulation provide a fresh perspective on slope drainage. Highlights • A new drainage measure, namely the air injection method for landslide mitigation is presented. • Formation process of the unsaturated zone by air injection is studied using physical model tests and numerical analyses. • Features of the air–water flow in the unsaturated zone at different injection pressures are analyzed. [ABSTRACT FROM AUTHOR]

In this study, some of the optimal parameters for a new-style marine axial flow fan are defined by using numerical simulation and experimental tests with a large marine axial flow fan, based on the analysis of the blade perforation’s influences on its internal flow field and aerodynamic noise characteristics. Test result shows that the noise reduction for the axial flow fan with perforated blade is about 3 dB when the blade perforation diameter D is 10 mm and its deflection angle α is 45°. The results of the study show that there is an inhibitory effect on the discrete noise of axial flow fan with perforated blade on the tip area, and its total noise level emerged as the fluctuated distribution characteristics with the increase in the perforation diameter D and reduced along with the increase in the deflection of perforation angle α, at the same time varied as a linear characteristics, which can be reasonably explained by the acoustic interference theory. The results of the study have also further confirmed that the improvement of the flow of axial flow fan with perforated blade helps to reduce the pressure pulsation amplitude caused by the turbulence of the blade surface boundary layer, thereby suppressing the back-flow and vortex from the pressure surface to the suction surface efficiently. It is indicated that the improved vortex shedding phenomenon at the blade trailing edge after perforation on the area of blade tip is the main reason for the aerodynamic noise reduction of axial flow fan. [ABSTRACT FROM AUTHOR]

Numerical simulation was carried out in three-dimensional and axisymmetric formulations for the hydrodynamics and mixing of bottom- and tangentially blown air with different temperatures in a cyclone chamber with local supply of tangentially blown air. To calculate vortex flows in the chamber, use was made of the most popular turbulence models k-ε, k-ω, and SA. It has been established that the best correspondence between the results of calculation and experimental data on hydrodynamic parameters (velocity and pressure) and air mixing under nonisothermal conditions is furnished by the k-ε and k-ω models of turbulence. Good agreement of the results of numerical simulation of vortex flows in the indicated chamber in three-dimensional and axisymmetric formulations has been obtained. [ABSTRACT FROM AUTHOR]

A system with optimum thermal control and noise control is proposed to allow placement of servers at workspace for low operation office cost. A computational fluid dynamics (CFD) model is developed to predict the air flow and temperature distribution of the system. To improve the accuracy of the simulation, the geometry of the axial-flow fan is reproduced in detail and the rotor region is treated with the multiple reference frame model. A porous model is applied to describe the hydraulic and thermal behavior of the evaporator. The integrated system simulation model is validated by measurements. Four layouts of fans are proposed to analyze the airflow organization and temperature distribution. The inhomogeneity of the temperature field is quantitatively evaluated via information entropy and variance. The results reveal that the airflow organization scheme avoids the occurrence of an evident stagnant zone or a hot spot. There are low-velocity zones with insufficient heat transfer in the evaporator. Increasing the number of fans can improve the heat transfer and result in a more uniform temperature distribution. Setting up ventilation fans to increase the ventilation rate of the server is an effective way to meet the challenges of higher heat density. [ABSTRACT FROM AUTHOR]

This study presents a novel design of high-efficiency two-stage electrostatic precipitator (ESP). For its design, different electrode configurations were tested and the corresponding onset and breakdown voltages were measured and compared. Based on findings, an optimal arrangement was then defined and a novel design of a two-stage ESP prototype, using needle electrodes instead of long wires utilised in conventional ESPs, is realised. For comparison, a single-stage ESP was also built. The influence of various parameters on the performances of both two-stage and single-stage ESPs was evaluated numerically using 2D modelling and compared with the experimental ones for the same dimensions of laboratoryscale ESP. The numerical simulation was implemented using COMSOL Multiphysics package that uses finite element method (FEM) solver. The main investigated parameters are the electric potential, electric field distribution and collection efficiency under the loading conditions as a function of air flow velocity, magnitude and polarity of voltage, ESP geometry design (size, shape and number of discharge electrodes). It is shown that the collection efficiency of this novel ESP increases when decreasing air flow velocity; and its effectiveness is higher when using negative ionisation polarity. Also, the collection efficiency of this ESP could greatly improve the existing ESPs under the same applied physical conditions. [ABSTRACT FROM AUTHOR]

In this current contribution, a parametric investigation of air flow rate at the inlets of solar air collector was carried out. Through a developed Matlab code effort was made to show the effect of the air flow rate on solar collector outlet temperature. From the simulation results a database of outlet temperature and corresponding flow rate variation with time was created. Then, isotherm contours were deduced and plotted. For drying temperature kept constant at a given value regardless the meteorological conditions fluctuation, the flow rate variation with time was fitted by smoothing spline function. The simulation study was done for three different meteorological scenarios: Clear sky day, partly cloudy day and cloudy day. It has been found also that drying with variable flow rate at optimum temperature equal to 50 '1'C the amount of air that was aspired at the inlet was 1207.8 kg. By contrast, drying with constant flow rate a total 625.5kg of air was aspired and it might result in fluctuation in drying temperature which affects the dried product quality. Thus variable flow rate allows a gain ratio in the aspired air amount of 93% and better product quality. This is valid for clear sky day. In case of partly and cloudy day, flow rate gain ratio was 104% and 78% respectively. [ABSTRACT FROM AUTHOR]

ABSTRACT Lee, K.H. and Kim, T.G., 2018. Three-dimensional Numerical Simulation of Airflow in Oscillating Water Column Device. In: Shim, J.-S.; Chun, I., and Lim, H.S. (eds.), Proceedings from the International Coastal Symposium (ICS) 2018 (Busan, Republic of Korea). Journal of Coastal Research, Special Issue No. 85, pp. 1346–1350. Coconut Creek (Florida), ISSN 0749-0208. An Oscillating Water Column (OWC) is a wave energy converting technology that uses the compressed and decompressed airflow induced by the vertical oscillations of water column inside the chamber as a driving force of an airflow turbine. In this study, three-dimensional numerical simulations of a bottom-fixed OWC are performed to understand the interaction of an OWC device with regular waves. The open-source CFD model REEF3D is used, which is able to consider immiscible two-phases (air and water) using the Reynolds-averaged Navier-Stokes equations. The simulation capability of REEF3D is validated by comparison with experimental data for wave deformations caused by the OWC and air-flow fields and the airflow velocity in the chamber. The numerical results revealed that the CFD numerical tool REEF3D can successfully simulate wave deformations caused by wave-OWC interactions, and directly estimate an air velocity inside the chamber. In addition, it was found that a phase difference occurs between time series of free surface evolution and air velocity evolution. [ABSTRACT FROM AUTHOR]

Due to vertically thermal stratification in indoor spaces, the cooling load calculation is always a challenge in the design of stratified air distribution systems (STRAD), which in turn is crucial to determine the supply air flow rate and the cooling load to be removed by the air conditioning system. In this paper, several cooling load calculation methods, developed in the past 20 years and focused on STRAD systems, were briefly reviewed. It attempts to clarify these methods in terms of their advantages, limitations and suitable ranges of applications. Furthermore, series of numerical simulations with a total number of 56 cases were conducted, and the applications of a novel cooling load calculation method in STRAD systems were investigated. The reliability of the method was validated for STRAD systems with separated locations of return and exhaust grilles, when adopted in three typical spaces with different building heights, namely a small office, a large terraced classroom and a terminal building. Databases of effective cooling load factors ( ECLF i ) for different heat sources distributed in the three spaces were obtained and presented, which can be conveniently used to calculate cooling loads. In addition, the influences of return grill height on the occupied zone cooling load as well as the energy saving potentials of STRAD systems were also clarified. The results presented in this paper are helpful for the design and optimization of STRAD systems. [ABSTRACT FROM AUTHOR]