Numerical Simulation Of Airflow Research Articles

Numerical simulation of air flow and distribution in the blast system of blast furnace

A three-dimensional geometric model of the blast system of the 5500 m3 blast furnace was established in this study. The velocity distribution of the blast system was calculated by OpenFOAM, and the velocity distribution at cross sections of the round pipe and the branch pipe was analysed. The main conclusions are as follows: (1) When the hot air enters the branch pipe, the air flow speed gradually increases and reaches its maximum value (approximately 266.7 m/s) at the tuyere outlet. (2) When the hot air enters the round pipe from the main pipe, there is momentum loss. When the hot air further reaches the opposite side of the junction between the round pipe and the main (Tuyere 1#), the speed of the hot air in the round pipe decreases to the minimum. (3) The maximum air flow average speed of the tuyere outlet is located at Tuyeres 20# and 21# at the junction of the main pipe and the round pipe, which can reach 264.5 m/s. The minimum air flow average velocity of the tuyere outlet is located at Tuyeres 19# and 22#, approximately 258.5 m/s.

Numerical Simulation of Airflow in the Main Cable of Suspension Bridge with FPM Model

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

Numerical Simulation of Airflow and Dust Migration in Vacuum Vessel During Loss of Vacuum Accident for Updated CFETR

A loss of vacuum accident (LOVA) occurs during in-vessel component failure and air ingress. The airflow characteristics of a LOVA are determined by many factors like initial pressure, location of a break, and size of a break and have a great impact on dust migration, which could cause a serious explosion with incoming air and H2. In this paper, a computational fluid dynamics method is adopted, and the k-ε Shear Stress Transport model for airflow and the Discrete Phase Model for dust are used to simulate a LOVA with the updated Chinese Fusion Engineering Test Reactor (CFETR) tokamak device. The effects of initial pressure, break size, and break location on airflow during the LOVA are discussed, and the effects of dust size, break size, and break location on dust migration during the LOVA are investigated as well. The results indicate that the initial pressure and size of a break have a greater impact on airflow of a LOVA than the location of the break and that both the dust size and the characteristics of the airflow have a greater impact on the distribution of the dust. A break located in the upper port has even more dust chaos. This research is the basis for the safety analysis of the CFETR device, and it provides a reference for subsequent studies on dust removal, mitigation of dust explosions, and radioactive substances.

Influence of Morphological Parameters on the Flow Development within Human Airways

Anatomical airways parameters, such as length, diameter and angles, have a strong effect on the flow dynamics. Aiming to explore the effect of variations of the bifurcation angle (BA) and carina rounding radius (CRR) of lower human airways on respiratory processes, numerical simulations of airflow during inhalation and exhalation were performed using synthetic bifurcation models. Geometries for the airways models were parameterized based on a set of different BA’s and several CRR’s. A range of Reynolds numbers (Re), relevant to the human breathing process, were selected to analyze airflow behavior. The numerical results showed a significant influence of BA and the CRR on the development of the airflow within the airways, and, therefore, affecting the following relevant features of the flow: the deformation of velocity profiles, alterations of pressure drop, flow patterns, and, finally, enhancement or attenuation of wall shear stresses (WSS) appearing during the regular respiratory process. The numerical results showed that increases in the bifurcation angle value were accompanied by pressure increases of about 20%, especially in the regions close to the bifurcation. Similarly, increases in the BA value led to a reduction in peak shear stresses of up to 70%. For the ranges of angles and radii explored, an increase in pressure of about 20% and a reduction in wall shear stress of more than 400% were obtained by increasing the carina rounding radius. Analysis of the coherent structures and secondary flow patterns also revealed a direct relationship between the location of the vortical structures, the local maxima of the velocity profiles and the local vorticity minima. This relationship was observed for all branches analyzed, for both the inhalation and exhalation processes of the respiratory cycle.

A Numerical Simulation of Air Flow in the Human Respiratory System Based on Lung Model

A Numerical Simulation of Air Flow in the Human Respiratory System Based on Lung Model

Numerical simulation of airflow and dispersion in 3D street canyons: the effect of atmospheric temperature stratification

ABSTRACT Based on the Reynolds-averaged Navier–Stokes (RANS) method, a modified standard k-ϵ turbulence model with a source term rooted on Monin–Obukhov similarity theory was used to investigate the effects of temperature stratifications on the flow field and pollutant dispersion in 3D street canyons. The results showed that airflow and pollutant transport was highly dependent on temperature stratifications. The vortex velocity in the canyon varied with temperature stratifications. With the more unstable conditions, the centre of the vortex was closer to the ground, and the intensity and turbulent kinetic energy of the eddy increased. Because the source of pollution was located on the ground, the pollutants migrated to the leeward side of the building with the eddy and then moved upstream or downstream with the airflow. Under neutral conditions, the pollutants migrated to the leeward side first with the eddy in the canyon and then mainly migrated downstream with the airflow but rarely migrated to the upstream street canyons. However, under unstable conditions, the pollutant concentration in the upstream street canyons also increased, mainly because the intensity of the vortex increased, which made the pollutant easier to transport upstream. According to the results of the pollutant flux analysis, the turbulent fluxes on the top plane of the buildings were positive and increased significantly with the more unstable conditions, indicating that turbulent fluxes play a positive leading role in the dispersion of pollutants. The transverse transport of the pollutants was mainly dominated by convective motion, and turbulent transport was relatively minor.

Numerical Simulations of Air Flow and Traffic–Related Air Pollution Distribution in a Real Urban Area

With increasing urbanization, urban air pollutants are becoming more and more relevant to human health. Here, combined with meteorological observation data, a numerical simulation of typical urban blocks in Shanghai was carried out to understand the spread of air pollutants caused by road traffic sources (ground–level and viaduct–level). Firstly, we analyzed the wind environment characteristics. Then, we quantitatively analyzed the pollutant distribution profiles and the contributions of two pollutant sources (PSV). Finally, we analyzed seven urban morphological parameters based on ventilation efficiency indices. Results revealed the following. (1) Ventilation patterns within the architectural complex are determined by local geometry; (2) Pollutants released at ground level were dominant when the Z–plane < 8 m high, and pollutants released from the viaduct source were 0.8–6.1% higher when the Z–plane ≥ 8 m high; (3) From ground level to a height of 60 m, the spatially–averaged normalized concentration (C*) tended to decrease gradually with distance from the source. C* increased irregularly with an increase in distance between 60 m and 86 m. Above 86 m, C* tended to increase linearly; (4) Vertical profiles of C* around buildings were building–specific, and their rate of change was inconsistent with height increases. In general, the correlations between C* and VRw, and between C* and KEturb were larger on the windward side of PSV upstream buildings than on the leeward side. Buildings downstream of the PSV showed the opposite situation; (5) At pedestrian level, the seven urban morphological parameters had no significant correlation with VRw, Cir*, and Czs*.

Numerical simulation of airflow in naturally ventilated attics for different attic geometries

AbstractAttic 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.

Study of heat transfer in a heat exchanger with porous granules for use in transport

Currently, the problem of heat removal in transport is relevant. The paper presents numerical simulation of air flow through a granular layer with perforated granules 5 mm in diameter with different hole diameters: 0.5; 0.75; 1; 1.25; 1.5; 1.75; 2; 2.25; 2.5; 2.75; 3; 3.25; 3.5; 4 mm. Numerical simulation was carried out in the ANSYS Fluent (v. 19.0) software package for various air flow velocities. The analysis of the effect of the diameter of the hole in the granules and air velocity on the heat flux, outlet temperature and pressure drop was carried out.

CFD numerical simulation on diffusion and distribution of diesel exhaust particulates in coal mine heading face

Diesel equipment used in underground production and transportation will produce a large amount of diesel particulate matter (DPM), which seriously pollutes the fresh air in underground and endangers the life and health of miners. In order to study the diffusion and distribution of DPM, this paper based on CFD numerical simulation technology, carries out numerical simulation of airflow and DPM field in heading face. The results show that from 15 s to 60 s, DPM continuously accumulates in the blind zone of the airflow and on both sides of the monorail locomotive, with the DPM concentration greater than 1.2 × 10−7 kg/m3. At this time, the DPM cloud is 60 m in the horizontal direction, and shows a distribution characteristic of high in the middle and low on both sides. When T = 90 s, part of DPM diffuses to the roadway exit. At this time, in the entire roadway, starting from a section of 23 m away from the heading face, the DPM concentration sharply increases, reaching a peak of 2.91 × 10-7 kg/m3 at 33 m. Then it begins to decline slowly. The research results are of great significance to clean production in mines.

Numerical simulation of air flow and heat transfer in air refrigerated containers using clean energy technologies

Air refrigerated containers are important links and key equipment for air cold chain transportation. The refrigerated container cools the goods through the cold air circulation in the container to achieve the purpose of refrigeration. The key to the design of aviation refrigerators lies in the numerical simulation of the cold air flow and temperature distribution in the containers to determine the best air duct design and optimal air outlet arrangement. This article briefly analyzes the structure of the air refrigerated container, establishes the mathematical and physical models for numerical analysis, and then analyzes the two methods. At the same time, temperatures are tested in physical container with temperature measuring devices and conducts a comparative analysis with numerical simulation. The results show that the existing top on the basis of the air supply, assign a flow channel to each small tuyere and remove the small tuyere beside it. This situation is better for both flow and heat transfer. Temperatures in tests are similar with numerical simulation.

Numerical Simulation of Air Flows in the Loading Chute of an Aspiration Shelter with Multistage Recirculation Air Seal

We consider the process of multistage technological recirculation of aspiration air into transfer chutes, i.e., the return of aspirated air from the shelters of the technological equipment back to the technological process with an aim to reduce energy losses by creating aerodynamic drag in the path of motion of ejection air and maintaining the required values of thermal parameters in the equipment. It is recommended to equip the chutes with single-stage recirculation seals with minimum possible angles of air feed against the flow ejected by the reloaded bulk material, which would increase the energy efficiency of ventilation systems and decrease the amount of harmful substances ejected into the atmosphere.

Numerical simulation of air flows in the loading chute of an aspiration shelter with a multistage recirculating air seal

Рассмотрена многоступенчатая технологическая рециркуляция аспирационного воздуха в перегрузочные желоба ― возврат аспирируемого от укрытий технологического оборудования воздуха обратно в технологический процесс с целью снижения энергетических затрат за счет создания аэродинамического сопротивления на пути движения эжекционного воздуха и поддержания требуемых теплофизических параметров в оборудовании. Рекомендуется оснащать желоба одноступенчатыми рециркуляционными затворами с минимально возможным углом подачи воздуха навстречу потоку, эжектируемому перегружаемым сыпучим материалом, что повысит энергетическую эффективность систем вентиляции и сократит выбросы в атмосферу вредных веществ.

A numerical simulation of air flow in the human respiratory system for various environmental conditions

The functions of the nasal cavity are very important for maintaining the internal environment of the lungs since the inner walls of the nasal cavity control the temperature and saturation of the inhaled air with water vapor until the nasopharynx is reached. In this paper, three-dimensional computational studies of airflow transport in the models of the nasal cavity were carried out for the usual inspiratory velocity in various environmental conditions. Three-dimensional numerical results are compared with experimental data and calculations of other authors. Numerical results show that during normal breathing, the human nose copes with heat and relative moisture metabolism in order to balance the intra-alveolar conditions. It is also shown in this paper that a normal nose can maintain balance even in extreme conditions, for example, in cold and hot weather. The nasal cavity accelerates heat transfer by narrowing the air passages and swirls from the nasal concha walls of the inner cavity.

Optimization of ventilation of an indoor ice rink by numerical simulation of air flows

An important task in the design of objects with artificial ice cover is to provide them with a modern ventilation and air conditioning system, which allows maintaining the parameters of the air environment in the volume of the arena’s premises. A properly organized air exchange with an accurately calculated flow rate should ensure stable and comfortable air parameters on the roller for various zones. However, due to the complexity of the picture of thermal, mass transfer and air processes occurring during the operation of the ice arena, standard design techniques often do not allow to obtain the desired result. Therefore, at the present stage, it is extremely urgent to raise the quality of design of these objects, which can be done using the capabilities of the computer 3D-modeling method. At the moment, in the Russian Federation, modeling of air flows in the design of indoor ice platforms is used only in the construction of large facilities of national scale. This work presents a practical study on the possibility of using the method of numerical computer modeling to develop solutions to improve the ventilation systems of an existing facility of regional significance.

Numerical Simulation of Air Flow and Temperature Distribution in Volumetric Solar Receiver Consisting of a Porous Medium

Numerical Simulation of Air Flow and Temperature Distribution in Volumetric Solar Receiver Consisting of a Porous Medium

Numerical simulations of airflow and convective heat transfer of a sow

Effective ventilation reduces heat stress in sows. A numerical study was carried out to investigate the effects of airspeed and direction on the convective heat transfer around a sow having different postures and body mass. The convection characteristics of a sow were analysed in a virtual wind tunnel using computational fluid dynamics (CFD) tools. The four postures of the standing, sitting, reclining and lateral lying were included. The investigated sow masses ranged from 130 kg to 340 kg. The results show that: 1) The general convective heat transfer was higher when the sow was standing or sitting postures rather than in a reclining or lateral lying posture; 2) Wind direction affects the sow convective heat transfer coefficient. The convective heat transfer coefficient of a sow was largest when it was standing or sitting with the body axis 60° to wind direction. When reclining or lateral lying sow axis at 45° to wind direction, the convective heat transfer coefficient was the largest; 3) The convective heat transfer coefficient of a single sow can be used to predict the convective heat transfer coefficient of a sow amidst rows of multiple sows; 4) Sow body mass negatively affects the convective heat transfer coefficient; 5) The convective heat transfer coefficient of the sow's trunk is relatively low compared with other parts such as the legs, head etc. Based on these results, when a sow needs to be cooled during hot conditions, an oblique airflow is recommended, and airflow speed around the sow's trunk should be increased as much as possible. • Lowest sow heat transfer coefficient in reclining posture compared to others. • Airspeed and direction affected sow convective heat transfer coefficient. • Local convective heat transfer coefficient on trunk lowest compared to others. • Equations for estimating sow's convective heat transfer coefficient established.

Numerical simulation and trumpet optimization of the inside inhaling and outside pressing dust collector

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.

Application of double glazed façades with horizontal and vertical louvers to increase natural air flow in office buildings

The results of previous researches clearly indicate that the main concern in applying double skin façades (DSF) is overheating of the cavity and increasing the cooling energy consumption in warm seasons. The present study intends to consider the excessive heat trapped between two skins of double glazed façades in hot arid climates as a driving force to reinforce the natural airflow across the floors of an office building. To meet this purpose, numerical simulation of airflow and heat transfer inside the cavity of the double glazed façades and the adjacent floors, as well as the effect of different types of solar shading systems in horizontal and vertical modes on the airflow has been investigated using the CFD technique. The results show that the stack effect formed inside the cavity has enough power for air suction from the floors of the building and reinforcement of the natural airflow. The type of shading device has a significant effect on the airflow behavior and the heat transfer rate in the facade. In double skin facades with horizontal louvers, the buoyancy forces inside the cavity are stronger and the ventilation rate in the building floors is higher than the model with vertical louvers. On the other hand, due to the stronger convective flow in the cavity with horizontal louvers, the heat flux on the interior glass is higher than the cavity with vertical louvers and part of the heat inside the cavity is transmitted through the interior skin to the occupied spaces.

Numerical simulation of air flow in needle-to-cylinder electrohydrodynamic device

The paper presents the methodology and results of numerical simulation of the flow induced by corona discharge obtained with open-source environment Multiphysics Object-Oriented Simulation Environment (MOOSE) framework released by Idaho National Laboratory. Coupled system of governing partial differential equations is solved for the values of electric potential φ and space charge density ρq. The solution is used to calculate the spatial distribution of body force acting on the fluid as FEHD = ρq∇φ. The body force is subsequently introduced as a source term in Navier-Stokes equations solved in MOOSE for the value of fluid velocity. The results are presented as velocity profiles at the outlet of the flow generator and integrated to yield volumetric flow rate and the efficiency of the device. Comparison of the results with data available in literature reference for similar configuration shows satisfactory agreement.