Airflow Model Research Articles

Natural ventilation versus air pollution: assessing the impact of outdoor pollution on natural ventilation potential in informal settlements in India

Despite the proven benefits of natural ventilation (NV) as an effective low-carbon solution to meet growing cooling demand, its effectiveness can be constrained by poor outdoor air quality. Here, we propose a modeling approach that integrates highly granular air pollution data with a coupled EnergyPlus and differential equation airflow model to evaluate how NV potential for space cooling changes when accounting for air pollution exposure (PM2.5). Given the high vulnerability of low-income populations to air pollution and the dearth of energy and thermal comfort research on informal settlements, we applied our model to a typical informal settlement residence in two large Indian cities: New Delhi and Bangalore. Our results indicate that outdoor PM2.5 levels have a significant impact on NV potential especially in highly polluted cities like New Delhi. However, we found that low-cost filtration (MERV 14) increased the NV potential by 25% and protected occupants from harmful exposure to PM2.5 with a minor energy penalty of 6%. We further find that adoption of low-cost filtration is a viable low-carbon solution pathway as it provides both thermal comfort and exposure protection at 65% less energy intensity—energy intensity reduced to 60 kWh m−2 from 173.5 kWh m−2 in case of adoption of potentially unaffordable full mechanical air conditioning. Our work highlights ample opportunities for reducing both air pollution and energy consumption in informal settlements across major Indian cities. Finally, our work can guide building designers and policymakers to reform building codes for adopting low-cost air filtration coupled with NV and subsequently reduce energy demand and associated environmental emissions.

Vibration energy harvesting enhancement of a plate interacting with subsonic airflow in a narrow gap

In this study, the vibration energy harvesting of a plate interacting with subsonic airflow in a narrow gap by using a giant magnetostrictive-piezoelectric (GMP) energy harvester is investigated. To improve the performance of the energy harvesting, the effects of the instability and the dynamic bifurcation of the plate on energy harvesting performances are studied. The GMP harvester is integrated in the nonlinear energy sink (NES-GMP) to harvest the vibration energy concentrated by the NES. The equations of motion of the system are derived by using the Hamilton principle based on the nonlinear plate theory and the incompressible airflow model. The model of the subsonic airflow in a narrow gap is established with fourth degrees of freedom by the linear potential flow theory. The stability of the plate is analyzed by monitoring the natural frequencies of the system, and the dynamic bifurcation properties of the plate are analyzed by the Poincaré maps and the bifurcation diagrams. The simulation results show that the harvested energy from the instability state of the plate is more significant than that from the stable state. The variation of the harvested energy when the plate changes from the stable state into the divergence is larger than the variation of the harvested energy when the plate changes from the divergence state into the flutter state. Furthermore, the periodic-n motions can enlarge the harvesting performance significantly but the quasi-periodic motions and the chaotic motions have little effect on the improvement of the harvesting performance.

Numerical and Experimental Determination of the Wind Speed Value Causing Catastrophe of the Scissor Lift

The current work is devoted to the numerical determination of the wind speed value, which can cause the overturning of the mobile elevating work platform of the scissor lift type. In the first step of the analysis, the scaled model of the real vehicle is prepared. In the second step, the model is used in the aerodynamic tunnel to determine the aerodynamic force values and moment, which act on the vehicle. The three different configurations of the work platform are considered, namely: (a) The work platform raised to the maximum height with an additional bridge extended, (b) the work platform raised to the maximum height, and (c) the work platform half raised. In each position, the direction of the wind is changed from the range from 0° to 180° with an increment equal to 15°. In the next step of the analysis, the CFD simulations are carried out. The ANSYS Fluent R22 software is used. As a model of turbulent airflow, the standard k-ε with standard wall function is adopted. The obtained experimental results are used to verify the numerical model. A very good agreement between the results of the experiment and the results of numerical simulations is obtained. As the main result of the numerical study, the values of the tipping moment and corresponding wind speed that cause the overturning of the analyzed real scissor lift are determined. It occurred that the lowest value of the wind speed is obtained for the first variant of the vehicle configuration V1crt = 22.315 m/s for the angle of the wind speed direction β = 30° and the highest one for the third variant V3crt = 34.534 m/s and β = 15°, without any persons on the work platform. The presence of human beings on the work platform is also considered.

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.

Computational Modelling of Airflow and Heat Transfer during Cooling of Stacked Tomatoes: Optimal Crate Design

A 3D computational fluid dynamics (CFD) model was developed to predict the airflow and heat transfer in half of a pallet layer of tomatoes. The numerical and experimental results were compared, and a good agreement was obtained between both results using the root-mean-square error (RMSE) and absolute relative deviation (ARD) values as criteria. The validated CFD model was then used to minimise the product temperature heterogeneity by optimising the airflow rate and the crate design. A downward flow of the air along the central parts of the crates and an upward flow close to the lateral walls of the crates were observed. Three different total ventilated areas (TVAs) were tested to study their influence on the product temperature uniformity and cooling rate. The MTD and ATD decreased from 6.8 to 3.5 °C and from 1.5 to 0.7 °C, respectively, when the TVA was increased from 11 to 15%.

Numerical simulation and experimental research of fiber motion in vortex spinning

The application of high speed air flow in the textile field represents the frontier development direction in this field. However, the coupling mechanism between air flow and fiber is extremely complicated which greatly limits the development and application of new textile technologies. For this reason, this research study is intended to focus on the common cutting-edge basic scientific problem of the air-flow-fiber coupling mechanism, the vortex spinning technology is taken as a breakthrough point for research. Three-dimensional numerical models of air flow in vortex spinning nozzle and a free-end fiber were established. The hybrid grids including the structured hexahedral grids and the unstructured tetrahedral grids were used to divide the air-flow computational region, the realizable κ- ε model was used to solve the turbulent characteristics of air flow, and the wall function method was used to solve the air flow in the near wall region. The displacement and deformation of a single free-end fiber under the action of the air-flow force was solved by the second-order nonlinear double asymptotic method and interpolation method. The dynamic twist process of a free-end fiber was simulated in three-dimensional space by taking into account the fiber characteristics, such as straightening, bending, and torsion. In addition, a high magnification microscope was used to observe the free-end fiber motion during the spinning process. The results show that the numerical simulation is consistent with the experimental observation, proving that dynamic numerical simulation can solve difficult problems in the unobserved dynamic twisting process, and this deepens the understanding of the spinning mechanism in vortex spinning.

Nonlinear Modeling of an Automotive Air Conditioning System Considering Active Grille Shutters

This paper expands upon the state of the art in nonlinear modeling of automotive air conditioning systems. Prior models considered only the effects of the refrigerant compressor and the condenser fan. There are two new aspects included here. First, we create a mathematical model for front-end underhood airflow, considering vehicle speed, condenser fan rotational speed, and active grille shutter position. In addition, we present a new model for the power consumption of the vehicle associated with aerodynamic drag caused by underhood flow, as well as a fan power model which accounts not only for changes in rotational speed but also changes in flow rate. The models developed in this paper are coded in MATLAB/Simulink and assessed for various vehicle driving conditions against a higher-fidelity vehicle energy management model, showing good agreement. By including the active grille shutters as a controllable actuator and the impact of underhood flow on vehicle drag and fan power consumption, control schemes can be developed to holistically target reduced energy consumption for the air conditioning system and, thus, improve the overall vehicle energy efficiency.

Numerical simulation of the spatial and temporal distributions of the downwash airflow and spray field of a co-axial eight-rotor plant protection UAV in hover

The downwash airflow of a multi-rotor unmanned aerial vehicle (UAV) in hover can improve the penetration rate of droplets in the canopy of fruit trees, but the uncertain distribution of the downwash airflow can also lead to the generation of uneven distribution of droplets. With a co-axial eight-rotor plant protection UAV as the research object, the computational fluid dynamics (CFD) method is adopted in this study to establish the coupled flow field model of the downwash airflow and the two-phase flow model of airflow-droplets in hover. The spatial and temporal distribution law of the downwash airflow is analyzed, and the impact of the motion law of the droplets in the spray field is investigated. The results show that the downwash airflow shifts from an unsteady state to a steady state over time. Various wind vortices such as wake vortex, ground diffusion airflow, and vortex ring are generated during the evolution process, with a “negative velocity channel” of downwash airflow velocity identified in the central region under the rotors. The farther the airflow is from the rotor, the larger the area field of wake vortex airflow. Consequently, there is a gradual coupling of the left and right adjacent wake vortices from mutual independence, with the “spiral effect” of the downwash wind field offset by the mutual coupling of the upper and lower rotors of the UAV. When the installation position of the nozzle falls within the below-rotor region, the distribution of droplet deposition becomes more penetrative than the central axis installation position of the nozzle. It indicates that the below-rotor installation position of the nozzle can prevent droplets from entering into the coupling region of the trailing vortex, which reduces droplet drift. According to the field test, the measurement and simulation results of the downwash air velocity are consistent, with the minimum and maximum relative error reaching 4% and 29%.

An experimental test for gas pressure measurement within a realistic crack in concrete

Evaluating fluid leakage rates through cracks in concrete structures is essential in many fields (nuclear safety, fluid storage structures, durability of structures subjected to environmental conditions). In previous works, the authors proposed experimental procedures to study the water (Rastiello et al., 2014, 2018) and air (Tailhan et al., 2018) leakage processes through cracking concrete samples under Brazilian loading conditions. In a recent work, Tailhan et al. (2020) proposed a critical analysis of their own air permeability experimental setup considering an idealized parallel-plate system equipped with additional pressure sensors inside the crack. They showed that calibrating air flow models based on this experimental setup (and, more generally, experimental setups using “large” pressurized vessels placed upstream/downstream of the cracked sample) requires the knowledge of the pressure distribution inside the crack and that simply knowing the pressures inside the upstream and downstream chambers can lead to a misinterpretation of experimental results. In the present paper, a similar experiment is performed on a so-called “realistic crack” (i.e., representative of a crack surface in a split concrete block) molded in room-temperature-vulcanizing silicone equipped with internal pressure sensors. The results obtained show that knowing the real pressures at the inlet and outlet sections of the crack is even more important than in the case of the parallel-plate channel. Indeed, in that case, additional non-linear effects are observed in the mass flow-rate vs. square pressure gradient relation due to the geometry of the crack. Moreover, the crack geometry strongly affects the pressure drops measures at the inlet and outlet crack sections. These results clearly illustrate that attention has to be paid to interpreting experimental results on real cracks in concrete in the absence of pressure measures inside the crack. To the best of the authors’ knowledge, no experimental setups of this kind exist.

Simple decision-making model for orchard air-assisted spraying airflow

Airflow speed is one of the three factors of air-assisted spraying. Optimizing the matching model between airflow speed and target canopy characteristics is an effective way to improve the orchard precision spraying technology, as airflow can significantly affect droplet deposition and drift loss. A simple model of airflow speed was established in this study. First, air-assisted spraying experiments were carried out on a standard simulation canopy to study the airflow speed depended on canopy width, leaf area index, and porosity rate. Second, determined by Ribbon Method and verified by droplet drift data, the airflow speed through the canopy was between 0.5 m/s and 0.7 m/s. Third, multiple tests were carried out under standard simulation canopy with different characteristics, and the airflow speed model was established ultimately: with a fixed leaf area index (LAI), the relationship between canopy upwind boundary airflow speed and canopy width satisfied the exponential model (y=aebx), and the coefficients a and b are well related to the density of branches and leaves in the canopy. When LAI=3.456, y=2.036e1.5887x, R2=0.994; LAI=1.728, y=1.639e1.445x, R2=0.972. Orchard growers can acquire needed airflow speed through this simple model, it is quick and precise and appropriate to most growth periods of a variety of fruit trees, such as apples, pears, and vines. Keywords: airflow speed, canopy width, porosity rate, LAI, air-assisted spraying DOI: 10.25165/j.ijabe.20231602.6849 Citation: Wang X, Feng Y R, Fu W, Qi J T, Song J L. Simple decision-making model for orchard air-assisted spraying airflow. Int J Agric & Biol Eng, 2023; 16(2): 23-29.

Construction of pressure characteristics of a centrifugal radial fan using ANSYS CFX software package

Purpose. Improve the design and pressure characteristics of the centrifugal radial fan (CRF), reduce costs and design time by using modern design methods. Methods. Analytical study of the energy characteristics of the CRF using CFD software packages. Three-dimensional modeling of the flow of air in the flow part of the fan. Results. The paper describes the peculiarities of construction of the pressure characteristic of a centrifugal radial fan using the ANSYS CFX program. Numerical simulation of the flow was carried out to improve the initial indicators at the preliminary stage of the design of the CRF. This approach allows reducing costs and design time compared to the experimental approach and provides an opportunity to improve and analyze the performance of the fan and its design without manufacturing it. The use of a calculation complex of programs for the justification and analysis of the design results provides an opportunity to see the picture of the pressure distribution along the flow part, the field of velocity vectors and the movement of the air flow. By means of numerical modeling of the spatial air flow in the flow part of the fan, choosing the SST-turbulence model, the regularity of the change in the pressure characteristic of the fan was the distribution of velocities and pressures in different elements of the air conditioning system, at different values of the mass flow of air, was determined. An analysis of the change in total and static pressure in the flow part of the CRF was performed: in the stator – an inlet nozzle, in the rotor – a closed type impeller, and in the stator – made in the form of a snail. The question of the dependence of the total and static efficiency on the mass flow rate of the fan is also considered. Conclutions 1. Studies of the process of construction of the pressure characteristic of the CRF showed that the proposed approach allows you to reliably estimate the parameters of the fan’s operating modes, determine the main features of the change in determined. As a result of the calculation, efficiency and the distribution of full and static pressure in the elements of the flow part for its further improvement. 2. A distinctive feature of the proposed method of constructing the pressure characteristic is that in the early stages it is possible to predict the hydrodynamic parameters of the flow part of the designed fan without creating its solid-state model. And based on the results of a numerical study of the spatial air flow, it is possible to quantitatively and qualitatively analyze the elements of the flow part of the fan and specify their geometric dimensions for further calculation based on average parameters. 3. The ANSYS 19.0 CFX software complex allows you to immediately display changes in the design of fan assemblies and obtain the results of a numerical study of the spatial air flow in the flow part of the fan. Using the proposed graphic materials, it is possible to visually observe the processes taking place in the flow part of the CRF. The possibility of numerical calculation of the parameters of interest is also shown. 4. The creation of a real CRF to evaluate its performance requires significant funding and is time- consuming, while the use of CFD is fast and cost- effective. The ANSYS 19.0 CFX software package makes it possible to visually present a picture of the behavior of a wide range of process parameters that occur in the flow part of the fan and to show their relationship with the features of the geometry and dimensions of the fan. Keywords: total pressure, static pressure, nozzle, impeller, volute, CFD, mass flow, total efficiency, static efficiency.

Analyzing the effects of passive design strategies on building ventilation performance and thermal comfort using simulation-based approach

One of the sustainable approaches to improving indoor thermal comfort and building ventilation efficiency, particularly in developing and populated countries, is to implement the optimum passive design solutions. However, the interaction between ventilation performance, indoor thermal comfort, and passive design features of buildings is scarcely studied in the domain of airflow modeling. Therefore, this study aims at assessing the ventilation performance and indoor thermal comfort with regards to passive design strategies, specifically, opening characteristics such as the Opening to Wall ratio (OWR) and Window to Wall ratio (WWR) in a Computational Fluid Dynamics (CFD) environment. The CFD simulations run is found pivotal for determining the spatial variation of Predicted Mean Vote (PMV) and Predicted Percentage Dissatisfied (PPD) to gauge thermal comfort and the natural ventilation performance in terms of air change rate per hour (ACH). The proposed methodology is implemented in classroom spaces of an academic building located in a warm and humid region. In the study, a field investigation is carried out to collect precise temperature and air velocity data needed to validate the resulting CFD model. The findings show that increasing OWR and WWR percentages can enhance ventilation efficiency and indoor thermal comfort.

METAQU; A STRATEGI TO ENHANCE READING QUR'AN CAPABILITY THROUGH WALI ASUH

This study aims to determine the improvement of students' ability to read the Qur'an through the talqin method. The method used is a qualitative approach with the type of case study, Data collection techniques using observation, interviews, and documentation. While the data analysis uses the air flow model which consists of three stages, namely: reducing data, presenting data, then drawing conclusions/verification. The results showed that the talqin method is an appropriate learning method in increasing the students' ability to read the Qur'an, and the talqin method is very influential on the improvement of the students' ability to read the Qur'an. This study implies that the talqin method can facilitate students in learning to read the Qur'an, especially in increasing the ability to read the Qur'an of students.

Terrestrial laser scanning for 3D mapping of an alpine ice cave.

Perennial ice deposits in caves are an underexplored component of the cryosphere preserving a largely untapped archive of long-term changes in landscape and climate whose existence is threatened by climate change. This study demonstrates how terrestrial laser scanning (TLS) can be used to fully and accurately (registration accuracy < 1 cm standard deviation of point differences) assess the geometry of an ice-bearing cave in the Eastern Alps (Tyrol, Austria). Three TLS campaigns and 255 scan positions were used to acquire point clouds with a high sampling density (2 cm average point spacing) in order to minimise shading effects and to assure a precise and highly resolved 3D documentation of the cave. A semi-automated registration and point cloud-processing approach adapted to the site-specific demands ensured a complete and error-minimised assessment of the cave's geometry serving as a solid basis for future quantifications of snow and ice content dynamics. Dominant cave surface structures were investigated by performing a multiscale principal component analysis (PCA) to identify a detailed and computationally efficient basis for future airflow modelling tasks.

Mechanics of the Prey Capture Technique of the South African Grassland Bolas Spider, Cladomelea akermani.

Spiders use various combinations of silks, adhesives, and behaviors to ensnare prey. One common but difficult-to-catch prey is moths. They easily escape typical orb-webs because their bodies are covered in tiny sacrificial scales that flake off when in contact with the web's adhesives. This defense is defeated by spiders of the sub-family of Cyrtarachninae-moth-catching specialists who combine changes in orb-web structure, predatory behavior, and chemistry of the aggregate glue placed in those webs. The most extreme changes in web structure are shown by the bolas spiders which create only one or two glue droplets at the end of a single thread. They prey on male moths by releasing pheromones to draw them close. Here, we confirm the hypothesis that the spinning behavior of the spider is directly used to spin its glue droplets using a high-speed video camera to observe the captured behavior of the bolas spider Cladomelea akermani as it actively spins its body and bolas. We use the kinematics of the spider and bolas to begin to quantify and model the physical and mechanical properties of the bolas during prey capture. We then examine why this species chooses to spin its body, an energetically costly behavior, during prey capture. We test the hypothesis that spinning helps to spread pheromones by creating a computational fluid dynamics model of airflow within an open field and comparing it to that of airflow within a tree, a common environment for bolas spiders that do not spin. Spinning in an open environment creates turbulent air, spreading pheromones further and creating a pocket of pheromones. Conversely, spinning within a tree does little to affect the natural airflow.

Comparison of the Efficiency of Cross-Flow Plate Heat Exchangers Made of Varied Materials

This paper discusses a mathematical model for airflow through a cross-flow plate heat exchanger. The exhaust air is used to heat the supply air. Three kinds of plates are considered: made of aluminium, copper, and steel. The purpose of this research was to verify which material used to build the plate heat exchangers uses the exhaust air heat more efficiently. The method of the Trefftz function was used to determine approximate solutions to the analysed problem. The results obtained for 1.2 mm-thick plates and for external winter, summer, and spring–autumn temperatures are discussed. The results indicate that if the efficiency and price of the metals are considered, then steel is the best material for the plate heat exchanger. Thanks to the use of thin steel plates and the reduction in air exchange time to a few minutes, a cheap and efficient cross-flow heat exchanger can be obtained.

Comparative modelling of inspiratory airflow and micron particle deposition patterns in monkey and human nasal airways

Laboratory animals have historically performed a vital function in evaluating health effects of human exposure to ambient particulate matter (PM). Due to the complexity of particle-laden flows and airway interactions that involve multiple species, in-depth knowledge of airflow and particle transport in both the non-human primate surrogates and human airways is still lacking. To advance the understanding in this field, this paper presents a numerical study that investigated the airflow and particle deposition characteristics of inhaled PMs in monkey and human nasal airways. Anatomically accurate macaca fuscata monkey and human nasal cavity models were reconstructed from CT images, micron particles with diameters less than 10 μm were included to conduct in silico exposure studies. Resultant particle deposition patterns were quantified by deposition enhancement factor (DEF) and deposition intensity (DI) along the airways to provide profound understanding of the similarities and differences in particle inhalation exposure characteristics across species. Anatomy comparison showed that the convoluted nasal passage of the monkey airway possessed higher level of complexity in terms of the surface-area-to-volume ratio compared to the two human nasal models, which could lead to higher evaluated nasal exposure to airborne particulate matter. Similar airflow patterns were observed from streamlines and wall shear stress distributions in all three nasal cavities of two species, with bulk air concentrated mainly in the middle and inferior meatuses in the nasal chambers. Despite the evidenced inter-subject deposition variations presented in all considered nasal cavity models, strong and similar micron particle deposition preferences with comparable DEF and DI levels were observed along the floor region of middle and inferior meatuses for both species. The methods and research findings presented in this work represent critical, initial steps towards establishing high-fidelity qualitative and quantitative linkages between the two species that enable more effective laboratory data extrapolations, improve study design, and facilitate validations of in vitro techniques currently being developed as part of international efforts to reduce or replace the use of animals in toxicity assessments for aerosol exposures.

Thermal performance assessment of a retrofitted building using an integrated energy and computational fluid dynamics (IE - CFD) approach

The comfort of the occupant in the indoor thermal environment can be efficiently analysed using the principle of computational fluid dynamics (CFD) technique. This can be modelled as a difference of measure of a region equivalent to air circulation and diffusion in/out of the area. Other parameters influence the room operating condition and energy consumption by the building systems directly and indirectly over a period of time. This paper represents how to use comfort theory and CFD concepts to do a computational study of building comfort and improve the energy performance of the building during the summer and winter seasons in the subtropical climate. The occupants’ overall comfort evaluation results in the chosen building are recorded, taking into account the suitable climate-responsive heating, ventilation and air conditioning approach and envelope systems. The thermal CFD simulation model used in this study incorporates the most current turbulence simulation methodology appropriate for airflow modelling in buildings. The numerical comfort analysis methodology is used to analyse the indoor thermal condition, considering the Cooled Beam cooling system and BioPCM as an envelope solution for possible retrofitting. The simulation findings show that the uniform temperature distributions observed during working hours are adequate and demonstrate improved energy performance by the building systems. Moreover, the results suggest that the use of advanced computational fluid dynamics techniques is a valuable method for the analysis of human comfort in indoor spaces.

Developing a mathematical simulation method for three-dimensional separated airflow at inlet of local exhaust devices

For local exhaust ventilation systems to be capable of removing contaminants reliably, accurate data on the velocity field around local exhaust devices is needed. The boundaries of the separation airflow at its inlet must be determined as a prerequisite for shaping leading edges of the exhaust hood. This shaping technique makes it possible to reduce local resistance, improve acoustic properties, increase contaminant capture efficiency and reduce electricity costs associated with operating ventilation systems in buildings. The goal of our study is to develop a discrete mathematical model of three-dimensional stationary separated airflow at the inlet of a rectangular exhaust duct. A novel aspect in our study is the mathematical simulation technique developed by us for 3D separated airflow at inlet of an exhaust hood. The discrete model was constructed using quadrangular vortex clouds comprising straight and curved segments, straight and curved horseshoe vortices, and closed curved vortex polygonal lines. We traced out the flow separation surface at the inlet of a sharp-edged rectangular exhaust duct and determined the axial airflow velocity using a computational procedure and a computer program designed by us. We compared our findings with the specially conducted experiment and different researchers' reports as well as values computed using complex analysis techniques for slotted exhaust hoods and our past computational data using the discrete vortex method for a square exhaust opening in non-stationary and quasi-axisymmetric settings. We found the results to be adequate. Our method can be used to determine the boundaries of vortex zones and trace out the velocity field at inlet of local exhaust hoods in a fully three-dimensional setting.

Numerical modeling of sneeze airflow and its validation with an experimental dataset.

In this study, we aimed at providing datasets using experimental results to validate the sneeze airflow. In addition, the boundary conditions for the sneeze simulation that could reproduce the sneeze airflow in the experimental results are presented and reviewed. The validation datasets were created by performing ensemble-average analysis with the experimental results of particle image velocimetry, and these were used to explore the boundary conditions to reproduce the sneeze airflow. As a result of the sneeze airflow reproduced by computational fluid dynamics simulation, the magnitude ranges of maximum velocity at the interface were observed to be 21.1-23.9m/s for males and 17.9-20.3m/s for females, which were higher than those of coughing. Compared with the experimental results, the root-mean-square error range for the overall airflow distribution was 0.19-0.23 m/s, whereas the error range for the magnitude of the maximum velocity at a criterion point was 0.03-0.08 m/s. The total sneezing airflow volume was in the range of 0.36-0.48 L, which was relatively low compared with that of coughing. Thus, this study provides important fundamental boundary conditions for computational fluid dynamics analysis, validated by experimental results, to interpret the spread of infectious particles by sneezing.