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The objective of this study is to implement a more realistic integrated analysis model for micro gas turbines by incorporating secondary flow and combustion efficiency into the existing model, which includes main engine components such as the compressor and turbine, and to validate this model by comparing it with test results. The study was based on the JetCat P300-RX, which has a maximum thrust level of 300 N. Simulations were performed using ANSYS CFX, employing the κ-ω SST turbulence model and a mixing plane interface between individual components. The eddy dissipation model (EDM), with a combustion efficiency of 90%, was used as the combustion model. A user subroutine was also applied for the power matching of the compressor and turbine to calculate the fuel flow rate in each iteration. For secondary flow, it was assumed that 3% of the total air flow rate would flow through the secondary path and be applied to the compressor and turbine. Simulations were conducted over a range of 30,000 to 104,000 RPM, with ground conditions evaluated, including altitude-simulated conditions. To validate the analysis model, engine performance metrics such as pressure ratio, air flow rate, fuel flow rate, and exhaust gas temperature (EGT) were compared with test results. The results demonstrated that errors were less than 5% for most engine performance metrics, except for EGT and fuel flow. The discrepancy in EGT was attributed to differences in the sensing methods, while the variation in fuel flow was found to be due to the lubrication system and losses due to the secondary air flow. Consequently, this study confirmed that the integrated simulation model accurately predicts engine performance. The results indicate that the integrated simulation model provides a more realistic prediction of overall engine performance compared to previous studies. Therefore, it can evaluate detailed thermo-fluid properties without the need for component performance maps, enhancing performance evaluation and analysis. [ABSTRACT FROM AUTHOR]

As the important component to guide the airflow in the classifier, installation position of the guide vane determines the width of the classification annular region and influences the flow field distribution. The influence of the guide vane positioning on the flow field in the annular region is analyzed through numerical simulation. The simulation results show the tangential velocities near the inner edge of the guide vanes increase, and the tangential velocity gradient decreases with decrease of the width of the annular region. The increases of turbulent dissipation rate near the guide vanes are beneficial to powder dispersion. However, the increases of turbulent dissipation rate near the rotor cage aren′t conducive to uniformity of the flow field. In case of the narrow annular region, the cut size gradually increases when the width of the annular region increases. However, when the width of the annular region continues to increase, the particle′s residence time become long, and the solid concentration increases significantly to increase the probability of particle aggregation. The reasonable range of the installation diameter of the guide vane in the classifier is between 504 mm and 524 mm. [ABSTRACT FROM AUTHOR]

Large-span arch greenhouse has gained widespread application in fruit and vegetable production in recent years, due to the convenient facility operation, high land use efficiency, suitability for multiple coverings, and external heat preservation. However, internal turbulence can often occur in the expansion of the span and height of the large-span arch greenhouse. The resulting uniformity of the greenhouse environment can then affect the efficient production of greenhouse crops. In this study, a multi-field coupled computational fluid dynamics (CFD) model was constructed to integrate the facility structure and tomato plant aerodynamics, according to agricultural industry demand. The research object was selected as the 20 m span large-span arch greenhouse in Laiwu district, Jinan City, Shandong province (36.14° N, 117.28° E), China. A systematic investigation was carried out to explore the influence of the height of the arch greenhouse on the spatial and temporal distribution and evolution of the turbulent structure inside the large-span arch greenhouse. An analysis was also made to clarify the relationship between the wind and the temperature distribution, turbulence intensity, summer ventilation, and cooling efficiency, and the height of the arch greenhouse. Seven kinds of large-span arch greenhouse were established with 4.5, 5.0, 5.5, 6.0, 6.5, 7.0 and 7.5 m heights. The results show that there was turbulent behavior in the large-span arch greenhouses, indicating the mostly double vortex in the section. The air-flow entered the greenhouse via the bottom vent on the windward side, then ascended along the lower side of the greenhouse film, and finally descended towards the roof area. There was a tendency for the stabilization in the position of the inflection point, as the ridge height increased beyond 6.0 m. Therefore, the better uniformity of air flow and temperature distribution were, the higher the uniformity of the greenhouse was. The large-span arch greenhouse with a height of 6.0 m shared the highest average flow velocity at the crop canopy, which was in the appropriate range and relatively high. The average temperatures were also relatively low, which were 0.404 ℃ and 0.026 ℃ lower than those of the arch greenhouse with a height of 5.5 and 6.5 m, respectively. The turbulence intensity of the large-span arch greenhouse with a height of 4.5-5.5 m was significantly higher than that with a height of more than 6.0 m. There was a small difference, after the ridge height exceeded 6.0 m. Once the height of the greenhouse was 4.5 m, the ventilation efficiency was 2.24. After that, the efficiency of ventilation decreased with the increase in the height of the greenhouse. There was a relatively high value when the ridge height reached 6.0 and 6.5 m. The ridge height of 7.0 m corresponded to the lowest ventilation efficiency of 1.60. The large span greenhouse with a 4.5 m ridge height exhibited the higher ventilation efficiency, but the lower air change rate. The large span greenhouse with a 7.5 m ridge height shared the lower air change rate and ventilation efficiency. The outstanding ventilation and cooling performance of the large-span arch greenhouse in summer was determined by many factors. In a 20 m long-span arch greenhouse with shoulder, a better structure was achieved with the ridge height of 6.0-6.5 m and the ridge height of 6.0 m, in order to better consider the factors of economy and safety. The finding can provide a strong reference to optimize a similar greenhouse configuration in the construction of the large-span arch greenhouse. [ABSTRACT FROM AUTHOR]

Odours used by insects for foraging and mating are carried by the air. Insects induce airflows around them by flapping their wings, and the distribution of these airflows may strongly influence odour source localisation. The flightless silkworm moth, Bombyx mori, has been a prominent insect model for olfactory research. However, although there have been numerous studies on antenna morphology and its fluid dynamics, neurophysiology, and localisation algorithms, the airflow manipulation of the B. mori by fanning has not been thoroughly investigated. In this study, we performed computational fluid dynamics (CFD) analyses of flapping B. mori to analyse this mechanism in depth. A three-dimensional simulation using reconstructed wing kinematics was used to investigate the effects of B. mori fanning on locomotion and pheromone capture. The fanning of the B. mori was found to generate an aerodynamic force on the scale of its weight through an aerodynamic mechanism similar to that of flying insects. Our simulations further indicate that the B. mori guides particles from its anterior direction within the ~ 60° horizontally by wing fanning. Hence, if it detects pheromones during fanning, the pheromone can be concluded to originate from the direction the head is pointing. The anisotropy in the sampling volume enables the B. mori to orient to the pheromone plume direction. These results provide new insights into insect behaviour and offer design guidelines for robots for odour source localisation. [ABSTRACT FROM AUTHOR]

The present study investigated the transmission of exhaled particles generated by coughing inside a car cabin, considering eleven different window opening configurations. The results indicated that particle dispersion and removal were mainly affected by the airflow, which was largely determined by the window opening configurations. Notably, efficient ventilation and a large number of open windows did not necessarily result in lower infection risk. Given the complex structure and formation of intricate airflow patterns within the cabin, airborne particles could spread throughout the cabin and deposit on the interior walls. As particles tended to escape or deposit rapidly within the first 10 s, precautionary measures were necessary during this time frame following a passenger's coughing activity. Furthermore, closing the window adjacent to the driver effectively reduced the proportion of exhaled particles passing through the driver's breathing zone due to the rear-in and front-out airflow pattern, thus mitigating the risk of infection. [ABSTRACT FROM AUTHOR]

The cleaning system is a critical component of the sugarcane chopper harvester, facing challenges such as high impurity rate, elevated power consumption, and an inadequate understanding of the cleaning mechanism. This study aims to simulate the process of removing extraneous matter (represented by sugarcane leaves) from the cleaning system by employing a coupling approach of computational fluid dynamics (CFD) and the discrete element method (DEM) to determine the speed of the extractor fan. Initially, a CFD model was established to analyze the airflow field within the extractor, and its accuracy was verified on a test bench for the cleaning system. Subsequently, a DEM model was developed for sugarcane billets and leaves, which was then integrated with the CFD model to form a gas–solid coupling model. The efficacy of this integrated model was confirmed through experimental measurements of impurity rate. Furthermore, a ternary quadratic regression orthogonal combination design was utilized in the gas–solid coupling simulation to assess the impacts of feed rate, leaf–stalk ratio, and extractor fan speed on impurity rate. Finally, the extractor fan speeds were obtained for various feed rates and leaf–stalk ratios under impurity rates of 5%, 6%, 7%, and 8%. This research can guide in controlling the extractor fan speed during sugarcane chopper harvester field operations and can serve as a foundation for extractor fan design. [ABSTRACT FROM AUTHOR]

Predicting the air flow pattern with proper accuracy and speed inside a building with natural ventilation is one of the important study topics of building design due to the economic importance of energy consumption. For this purpose, in this study, a chamber with certain dimensions and with natural connection has been investigated as a study sample to predict the air flow pattern and speed distribution with the help of regional models. Two air inlet and outlet valves were considered for natural air ventilation. After researching the previous models, the three-dimensional zone model coupled with heat transfer and air flow calculations (ZAER) was chosen as the basis for comparing the modeling results. In the following, after zoning, to improve the flow coefficient factor model, which is assumed to be a constant number, it was assumed to be variable and the results were recorded in different states. The behavior of the model has been checked in the flow coefficients between 0.3 and 1 in order to obtain the most optimal coefficient for the number of suitable cells. Comparing the results of the research with the results of other models and computational fluid dynamics (CFD) showed that the three-dimensional behavior of the flow shows better compatibility with the experimental researches. [ABSTRACT FROM AUTHOR]

Because of the lack of good seedling positioning during vegetable grafting, there are issues such as high labor costs and long grafting time. This article proposes a negative pressure suction seedling positioning method for seed leaves based on the characteristic parameters of cucumber spike wood, and designs a flexible adsorption positioning mechanism for spike wood. Firstly, the ventral surface curve trajectories of cucumber cotyledons were extracted using Matlab software, and then a shape-adaptive design was applied to the attachment surface of the flexible suction positioning mechanism, and a computational fluid dynamics model of the airflow field was established. By combining Fluent simulation analysis with orthogonal experiments, the effect of suction hole diameter, vacuum negative pressure value, suction hole quantity, and suction hole depth on the adsorption effect of the suction head was analyzed, the main and secondary factors and operational indicators that affect the adsorption effect are evaluated. The optimal parameter combination: suction hole diameter of 1.5 mm, vacuum negative pressure value of 2 kPa, suction hole quantity of 42, and suction hole depth of 2 mm, has been found. A verification experiment was conducted on a test bench, and the experimental results show that the success rate of leaf absorption using the optimal parameter combination is 97.69%, which indicates that the suction head is designed reasonably and meets the requirements of grafting. [ABSTRACT FROM AUTHOR]

Obstructive sleep apnea (OSA) is an airway disease caused by periodic collapse of the airway during sleep. Imaging-based subject-specific computational fluid dynamics (CFD) simulations allow non-invasive assessment of clinically relevant metrics such as total pressure loss (TPL) in patients with OSA. However, most of such studies use static airway geometries, which neglect physiological airway motion. This study aims to quantify how much the airway moves during the respiratory cycle, and to determine how much this motion affects CFD pressure loss predictions. Motion of the airway wall was quantified using cine MRI data captured over a single respiratory cycle in three subjects with OSA. Synchronously-measured respiratory airflow was used as the flow boundary condition for all simulations. Simulations were performed for full respiratory cycles with 5 different wall boundary conditions: (1) a moving airway wall, and static airway walls at (2) peak inhalation, (3) end inhalation, (4) peak exhalation, and (5) end exhalation. Geometric analysis exposed significant local airway cross-sectional area (CSA) variability, with local CSA varying as much as 300%. The comparative CFD simulations revealed the discrepancies between dynamic and static wall simulations are subject-specific, with TPL differing by up to 400% between static and dynamic simulations. There is no consistent pattern to which static wall CFD simulations overestimate or underestimate the airway TPL. This variability underscores the complexity of accurately modeling airway physiology and the importance of considering dynamic anatomical factors to predict realistic respiratory airflow dynamics in patients with OSA. [ABSTRACT FROM AUTHOR]

In engineering phase-change phenomena are found in a multitude of applications, ranging from refrigeration and air conditioning to steam turbines and petroleum refining. This study investigates the flow of moist air in a circular duct where water vapour condenses in contact with the cold wall of the duct. The investigation delves into the relationship between the condensation mass transfer rate, the heat transfer between the bulk flow and the wall, and the temperature of the wall. The volume of fluid model coupled with the Lee evaporation-condensation model was employed. Five simulations were carried out, involving different wall temperatures while maintaining the same inlet conditions. Condensation was more pronounced at lower wall temperatures, which aligns with the expectations. The heat transfer between the bulk flow and the wall decreased with the decreasing temperature difference. Interestingly, the findings revealed that the surface heat transfer coefficient increased as the wall temperature approached the temperature of the bulk flow. The success of the study suggests potential applications in optimising thermal management systems, with implications for industries where accurate predictions of moisture behaviour and heat transfer are crucial. [ABSTRACT FROM AUTHOR]

This study aimed to explore the variability in nasal airflow patterns among different sexes and populations using computational fluid dynamics (CFD). We focused on evaluating the universality and applicability of dimensionless parameters R (bilateral nasal resistance) and ϕ (nasal flow asymmetry), initially established in a Caucasian Spanish cohort, across a broader spectrum of human populations to assess normal breathing function in healthy airways. In this retrospective study, CT scans from Cambodia (20 males, 20 females), Russia (20 males, 18 females), and Spain (19 males, 19 females) were analyzed. A standardized CFD workflow was implemented to calculate R‐ϕ parameters from these scans. Statistical analyses were conducted to assess and compare these parameters across different sexes and populations, emphasizing their distribution and variances. Our results indicated no significant sex‐based differences in the R parameter across the populations. However, moderate sexual dimorphism in the ϕ parameter was observed in the Cambodian group. Notably, no geographical differences were found in either R or ϕ parameters, suggesting consistent nasal airflow characteristics across the diverse human groups studied. The study also emphasized the importance of using dimensionless variables to effectively analyze the relationships between form and function in nasal airflow. The observed consistency of R‐ϕ parameters across various populations highlights their potential as reliable indicators in both medical practice and further CFD research, particularly in diverse human populations. Our findings suggest the potential applicability of dimensionless CFD parameters in analyzing nasal airflow, highlighting their utility across diverse demographic and geographic contexts. This research advances our understanding of nasal airflow dynamics and underscores the need for additional studies to validate these parameters in broader population cohorts. The approach of employing dimensionless parameters paves the way for future research that eliminates confounding size effects, enabling more accurate comparisons across different populations and sexes. The implications of this study are significant for the advancement of personalized medicine and the development of diagnostic tools that accommodate individual variations in nasal airflow. [ABSTRACT FROM AUTHOR]

A horizontal air-assisted centralised metering device involves the use of conveying airflow for mixing and conveying during the seeding process, making it suitable for high-speed precision seeding. This study identified key structural parameters for the mixing component. Computational fluid dynamics (CFD) simulations were used to analyse the influence of the key structural parameters on airflow distribution and airflow velocity. The results suggested selecting a contraction section conical angle of 40° with maximal conveying airflow velocity and minimal airflow pressure loss. A mixing chamber length of 25 mm prevented the retention and blockage. An expansion section conical angle of 20° achieved higher airflow velocity within the expansion section. CFD-DEM (Discrete Element Modelling) coupled simulation were used to analyse the influence of mixing chamber height, seeding rate, and conveying airflow velocity on seed conveying performance. The results indicated that a mixing chamber height of 16 mm ensured stable seed acceleration, reduced the probability of seed-wall collisions. Seed collisions within the mixing chamber and expansion section increased noticeably along with the rising seeding rates. While airflow velocity in the range of 16–25 m s−1 facilitated timely seed conveyance and reduced seed-wall collisions. Verification experiments for the optimal parameter combination of the mixing component indicated that a conveying airflow velocity of 22 m s−1 resulted in the stability coefficient of variation of total seeding mass not exceeding 1.04 %, the uniformity coefficient of variation of seeding mass in each row not exceeding 3.61 %. This research offers valuable insights for structural improvements in the mixing component of the horizontal air-assisted metering device. • The influence of mixing component structure on airflow distribution was analysed. • The key parameter values of the mixing component were determined by CFD simulation. • CFD-DEM coupled simulation were used to analyse the seed conveying performance. • The mixing component for reducing seed-wall collision and retention was determined. [ABSTRACT FROM AUTHOR]

Gas-powered jet nebulizers deliver medications to treat acute and chronic respiratory diseases. Several authors have found large variations in the performance of these nebulizers, and despite numerous attempts, deposition efficiency remains low for both adults and pediatrics. Using a Sympatec laser diffraction system and computational fluid dynamics (CFD) simulations with SolidWorks Flow Simulations and Ansys Fluent, this study uses a comparative analysis to explore the influence of supply air pressure, nozzle orifice diameter, and baffle geometry on jet nebulizer performance. Performance was quantified using critical performance metrics including vacuum levels driving aerosolization rate, Mass Median Aerodynamic Diameter (MMAD), and aerosolization time. Preliminary findings suggest that the authors' 2.54 mm wide, semi-conical bar baffle may produce superior vacuum levels, and surpasses the performance of the leading commercial bar baffle geometry, the SideStream, with a smaller MMAD (1.7 versus 2.3 microns). The study confirms the predicted relationship between supply pressure and nebulizer performance: higher pressure improves airflow rates, jet velocities, and aerosol characteristics, and reduces aerosolization times. Additionally, a larger nozzle orifice diameter increases airflow rates and promotes better aerosol characteristics, highlighting a direct correlation between orifice size and nebulizer performance. This work underscores the importance of expanding research in nebulizer performance beyond the traditional focus on testing paired nebulizer/compressor systems. Copyright © 2024 American Association for Aerosol Research [ABSTRACT FROM AUTHOR]

To study the air‐suction separation mechanism of fresh tea leaves, this article adopts the coupling simulation method of discrete elements and computational fluid dynamics to conduct numerical simulation and experimental research on the movement of fresh tea leaves adsorbed by negative pressure air flow. In the gas–solid coupling model, three‐dimensional scanning technology is applied to establish a three‐dimensional model of fresh tea leaves with one bud and two leaves. Through the Fluent module in CFD, the negative pressure adsorption gas phase of the simulation process was established, bench tests were established, and parameters of the coupling model were optimized. Finally, the minimum error between the simulated value and the test value was 2.85% and the maximum error was 7.43%, indicating that the coupling model established had certain accuracy and could be theoretically analyzed according to the coupling model established. It is found that when the static pressure values of the adsorption surface are −120 Pa, −340 Pa, and −500 Pa respectively, the initial distance from the adsorption surface is 250–550 mm. It is found that fresh tea leaves with one bud and two leaves all fall to the pipe before adsorption, and then move to the adsorption surface. Under the same static pressure value of the adsorption surface, the initial falling distance of tea particles from the adsorption surface (250–550 mm) has a linear function relationship with the distance between the turning point and the adsorption surface. When the initial distance between falling tea particles and the adsorption surface is the same, the distance between the turning point and the adsorption surface is an exponential function when the initial position is 250–350 mm from the adsorption surface, and the distance between the turning point and the adsorption surface is a linear function when the initial position is 400–550 mm from the adsorption surface. [ABSTRACT FROM AUTHOR]

A design was proposed for a seed turbine installed within the distribution device to reduce the influence of surface slope variations on the uniformity of seeding mass at each row. Through a comparative analysis based on the computational fluid dynamics (CFD) 6 degrees of freedom (DOF) dynamic mesh model simulation and the bench test, the influence of five different stabilising turbines on airflow distribution performance was investigated. The type Ⅰ stabilising turbine, characterised by acute inlet and outlet angles, exhibited a smaller vortex region at the blade inlet and improved the conveying and mixing performance of the seed. A CFD 6DOF simulation experiment was conducted to investigate the influence of the type I stabilising turbine on the airflow field distribution. As the number of blades increased from 4 to 10, the stability and uniformity of the conveying airflow distribution were enhanced at the turbine outlet. Simulations using a comprehensive performance test platform of the planter evaluated the influence of stabilising turbines with different numbers of blades on uniformity during field operations at varying surface slopes. When the angles of the front-rear and lateral one-way oscillation combination, and the front-rear and lateral reciprocating oscillation combination varied within the range of −5°–5°, the stabilising turbine with 8 blades exhibited the smallest uniformity coefficient of variation of the seeding mass at each row. The values ranged from 4.1 % to 5.8 % for rapeseeds and from 3.8 % to 5.0 % for wheat seeds. • CFD simulations of airflow distribution in a seed distributing device. • Bench testing of seeding performance. • The stabilising turbines were studied and tested under different oscillation angles. • The uniformity performance was affected by oscillation angle and number of blades. • The stabilising turbine can improve the uniformity of seed flow distribution. [ABSTRACT FROM AUTHOR]

In this study, a new microwave infrared hot air rolling bed dryer (MIHRBD) was developed and computational fluid dynamics (CFD) techniques were introduced into the design process of the integrated drying system. The structure of the air distribution device was optimised to improve the airflow uniformity over the curved surface of the rolling bed in the microwave-hot air drying combined equipment. The research findings reveal that, across eleven models, the outlet airflow velocity stabilises once the number of mesh elements reaches 5 million, achieving significant computational accuracy at that point. Optimizing components like the uniform air distribution pipe, turbulence plates, and wind deflectors significantly enhanced airflow distribution uniformity by 52.1%. The best airflow and temperature distribution uniformity on the rolling bed surface was achieved when the inlet airflow velocity ranged from 1 to 3 m s−1, with minimum V d , U v and temperature non-uniformity coefficients of 0.007 m s−1, 7.2% and 0.2%, respectively. Validation tests on the MIHRBD pilot equipment showed that after optimizing the uniform air distribution device, the minimum temperature difference on the pleurotus eryngii surface was 3.1 °C. This confirmed the feasibility of the computational fluid dynamics method. Introducing hot air significantly enhanced pleurotus eryngii 's drying uniformity, with the Page model effectively predicting the MIHRBD drying process. This study provides technical support for future developments in this field of equipment manufacturing and drying process analysis. • A new microwave infrared hot air rolling bed dryer (MIHRBD) was developed. • Design of MIHRBD with advanced CFD for enhanced airflow uniformity. • Optimised uniform air distribution design increases airflow uniformity by 52.1%. • Colour quality of dried materials improved by optimised MIHRBD process. [ABSTRACT FROM AUTHOR]

This paper presents a lung model that allows the simulation of the airflow down to level 23 (alveoli). The flow trajectory along only one of every two airways at each bronchiole is calculated. The non-calculated airways are simulated by a User-Defined Function that prescribes the velocity profile at a surface located inside the calculated airway to the exit boundary of the truncated airway. The model is validated with experimental data of a real spirometry and it is used to predict the performance of a lung with bronchitis. The results show a decrease of the volume of air of about 13% with typical values of FEV1/FVC around 70.8% for the healthy lung and about 67% for the lung with bronchitis. This methodology can be adopted to simulate a full model of a human lung under healthy and bronchitis conditions while providing a practical description of the flow field within the lung. [ABSTRACT FROM AUTHOR]

Coronaviruses being capable of spreading through droplet contamination have raised significant concerns regarding high-capacity public rail transport, such as the metro. Within a rapidly moving railcar cabin, the internal airflow lags behind the bulkhead, generating internally induced airflow that accelerates droplet dispersion within a non-inertial reference system. This study investigates the impact of acceleration on the diffusion of cough droplets of varying sizes using computational fluid dynamics. The modified k–ε equation in ANSYS® Fluent was utilized to simulate droplet diffusion under different body orientations by adjusting the inertial force correction source term. Results indicate that droplets in the middle size range (50–175 μm) are primarily influenced by inertial forces, whereas smaller droplets (3.5–20 μm) are predominantly controlled by air drag forces. Regardless of facial orientation, the outlet of high-capacity public rail transport poses the highest risk of infection. [ABSTRACT FROM AUTHOR]

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

Unilateral cleft lip and palate (UCLP) nasal deformity impacts airflow patterns and pressure distribution, leading to nasal breathing difficulties. This study aims to create an integrated approach using computer-aided design (CAD) and computational fluid dynamics (CFD) to simulate airway function and assess outcomes in nasal deformities associated with unilateral cleft lip and palate (UCLP) after LeFort I osteotomy advancement. Significant alterations were observed in nasal geometry, airflow velocity, pressure dynamics, volumetric flow rate, and nasal resistance postoperatively, indicating improved nasal airflow. The cross-sectional area increased by 26.6%, airflow rate by 6.53%, and nasal resistance decreased by 6.23%. The study offers quantitative insights into the functional impacts of such surgical interventions, contributing to a deeper understanding of UCLP nasal deformity treatment and providing objective metrics for assessing surgical outcome. [ABSTRACT FROM AUTHOR]

This paper evaluates the thermal performance of ducts partially or fully buried in loose-fill attic insulation. The overall thermal resistance between the ducts and the attic is referred to as an effective R-value. This paper shows a strong dependency of assumed attic temperature on the effective R-value. Based on the results, the effective R-value can be about twice as much with an attic temperature of 130 °F [54.4 °C], compared to when the attic temperature is 80 °F [26.7 °C]. Thus, this paper provides a polynomial regression equation based on a large set of simulations to determine the effective R-value of buried ducts depending on attic temperature and whether the HVAC system runs in cooling or heating mode. Further, the work presented in this paper investigated the potential impact of convective airflow within the attic insulation, particularly around the ducts. The analysis was based on computational fluid dynamics (CFD) and indicated that convectional forces are presented around the exterior surface of the ducts, but with negligible impact on the overall heat balance between the duct and the attic space. [ABSTRACT FROM AUTHOR]

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

The study described here analyzed natural ventilation techniques, operated in a real building in the United Arab Emirates (UAE), to assist passive cooling. The assessment has been conducted by comparing digital simulation results and field measurements. Computational fluid dynamics (CFD) was used to retrospectively understand and quantify the monitored contribution of natural ventilation toward cooling the building. After calibrating the model with the field monitored data, the CFD simulations showed that the predicted ventilation strategies (buoyancy and stack effect to remove indoor heat; "wind catcher" effect to provide indoor passive cooling) contribute to lower the indoor temperature by an average of 0.7°C throughout the day. The outcomes of the study contributes to assist early stage design, with special regard to passive cooling via natural ventilation, to achieve more sustainable buildings. Nevertheless, while it is quite reliable to plan for main air flow and direction, in a real building alternative behavior might occur that is difficult to control and might affect the ventilation purpose and efficiency. [ABSTRACT FROM AUTHOR]

The multi-stage water spray cooling system of the space launch site involves a complex gas–liquid two-phase mixed cooling problem in the process of spraying water onto the rocket engine gas jet. To investigate the complex multiphase flow field of the interaction between the airflow and liquid water jet, the Mixture multiphase flow model is adopted, which is coupled with the vaporization equation and component transport model of liquid water. The computational fluid dynamics method is used to numerically analyze the mixing and cooling mechanism of low-temperature liquid jet in high-temperature and high-speed gas flow. The results show that mixing low-temperature liquid jets in high-temperature and high-speed airflow can cause the exchange of momentum and energy, resulting in pressure loss and temperature reduction in the gas phase flow field. Due to the acceleration of transverse airflow, the diffusion flow range of the jet is significantly increased, and violent vaporization occurs, which further consume a large amount of airflow energy. The mixing cooling effect of transverse airflow and liquid water jet is directly related to the mass flow rate ratio of the jet to airflow. In addition, directly designing liquid water jet orifices on the solid wall of the guiding device can achieve the effect of improving the gas flow field environment. This conclusion can provide theoretical reference for the thermal protection design of ground launch devices in space launch site. [ABSTRACT FROM AUTHOR]

Because of serious concerns about global warming, manufacturers have started phasing out high global warming potential (GWP) refrigerants in commercial refrigeration equipment (e.g., R-134a). As a potential replacement, propane (R-290) is an environmentally friendly refrigerant for commercial refrigeration equipment because its GWP is only three. However, propane is flammable and is therefore classified as a Class A3 refrigerant per ASHRAE Standards, so safety is a very important consideration when propane-based equipment is designed and deployed in buildings. In the event of a refrigerant leak, flammability of the refrigerant depends on the refrigerant's local concentration, which is highly affected by the indoor air environment, including temperature and air flow. In this study, a ventilation system attached to a commercial R-290 refrigeration device was designed to eliminate the flammability risk. Moreover, a computational fluid dynamics (CFD) model was developed to investigate the refrigerant leak, thereby evaluating effects of the ventilation system. The CFD model can visualize the flammable zones owing to the leak. [ABSTRACT FROM AUTHOR]

Summary: We investigate the transmission of aerosol particles in an airplane cabin with a joint approach using experiments and simulation. Experiments were conducted in a realistic aircraft cabin with heated dummies acting as passengers. A Sheffield head with an aerosol generator was used to emulate an infected passenger and particle numbers were measured at different locations throughout the cabin to quantify the exposure of other passengers. The same setting was simulated with a computational fluid dynamics model consisting of a Lagrange continuous phase for capturing the air flow, coupled with a Lagrange suspended discrete phase to represent the aerosols. Virtual measurements were derived from the simulation and compared with the experiments. Our main results are: the experimental setup provides good measurements well suited for model validation, the simulation does correctly reproduce the fundamental mechanisms of aerosol dispersion and simulations can help to improve the understanding of aerosol transmission for example by visualizing particle distributions. Furthermore, with findings from the simulation it was possible to crucially improve the experimental setup, proving that feedback between the numerical and the hardware world is indeed beneficial. [ABSTRACT FROM AUTHOR]

During the operation of the longitudinal axis flow threshing device of a combine harvester, the threshed materials form accumulations and blockages on both sides of the screen surface, severely affecting the harvesting process. To evenly distribute the materials on the screen and solve the blockage issue, a multi-wing curved combination centrifugal fan is designed to match the mass distribution of the threshed materials. The movement mechanism of rice threshed materials in the cleaning shoe of a longitudinal axis flow combine harvester is investigated using the coupled CFD-DEM simulation method. The cleaning efficiency and performance of the traditional straight-blade fan screen device and the newly designed cleaning device are compared and analyzed, and field tests are conducted. The results show that the trajectory of the threshed materials cleaned by the device equipped with the multi-wing curved combination centrifugal fan is consistent with the mass distribution of the materials separated by the longitudinal axis flow threshing device. The absolute value of the centroid velocity of the material group in the X/Y direction is greater than that of the traditional fan, indicating that the movement speed of the particle group in the optimized fan is greater than that of the traditional fan. Therefore, in the actual cleaning process, the optimized fan's air flow distribution more effectively accelerates the movement speed of the threshed materials, increasing the amount of materials cleaned per unit time, thereby improving the cleaning efficiency. Field comparative tests show that the designed cleaning device reduced the cleaning loss rate by up to 25.00% and the impurity content rate by 32.20%, achieving efficient and low-damage cleaning of the combine harvester. The study demonstrates the effectiveness of the proposed method for evenly distributing the materials and provides important reference for the study of other piled particle distribution systems. [ABSTRACT FROM AUTHOR]

In the aftermath of the COVID-19 pandemic, the urgent need for the rapid deployment of healthcare facilities propelled the rise of modular construction using an infill approach. In these modular, negative-pressure wards, the design of indoor airflow and pressure plays a crucial role in meeting the ventilation strategies required for isolation facilities. Accordingly, this paper focuses on modular negative-pressure wards employing an infill construction method and proposes an appropriate spatial pressure distribution to address the problem of air tightness degradation due to leakage. This study analyzed the indoor airflow and pressure distribution of a unit module corresponding to an infill. It aimed to examine whether the pressure difference with the adjacent room is maintained and to assess its effectiveness in isolating contaminated air. First, the airflow rate of the heating, ventilation, and air conditioning system in the unit module was calculated to ensure that it would meet the performance criteria of the negative-pressure ward. Afterward, based on the calculated rate, the study assessed the airflow and room-specific pressure within a typical floor, encompassing both the unit module and associated nursing support facilities. Here, the airflow in the external corridor of the typical floor was divided into two cases according to the pressure distribution: negative pressure and atmospheric pressure. The calculation results were compared using a computational fluid dynamics tool. The analysis results confirm that the air isolation performance is adequate as the pressure difference between adjacent rooms in the unit module and the typical floor was maintained at 2.5 Pa. Additionally, the indoor airflow in the negative-pressure isolation room formed a stable flow at a slow speed of 0.1–0.2 m/s, minimizing the possibility of air contamination from outside the isolation room. In particular, Case B of the typical floor design proposes a method to optimize the pressure distribution in the modular negative-pressure ward by designing the ventilation flow rate at atmospheric pressure level. Thus, this study emphasizes that atmospheric pressure design is appropriate when designing pressure in areas where negative-pressure control is difficult and can contribute to the design and improvement of similar medical facilities in the future. [ABSTRACT FROM AUTHOR]

To study the characteristics of nasal airflow in the presence of nasal cycle by computational fluid dynamics. CT scan data of a healthy Chinese individual was used to construct a three-dimensional model of the nasal cavity to be used as simulation domain. A sinusoidal airflow velocity is set at the nasal cavity entrance to reproduce the breathing pattern of a healthy human. There was a significant difference in the cross-sectional area between the two sides of the nasal cavity. Particularly, the decongested side is characterized by a larger cross-section area, and consequently, by a larger volume with respect to the congested side. The airflow velocity, pressure, and nasal resistance were higher on the congested narrow side. The temperature regulation ability on the congested narrow side was stronger than that on the decongested wider side. During the nasal cycle, there are differences in the nasal cavity function between the congested and decongested sides. Therefore, when evaluating the impact of various factors on nasal cavity function, the nasal cycle should be considered. [ABSTRACT FROM AUTHOR]

In this research, the escalating energy consumption challenges in data centers are addressed by optimizing airflow organization designs. Through the use of computational fluid dynamics (CFD) simulations, three different airflow strategies were evaluated and improved: underfloor precision air conditioning, inter-column air conditioning, and backplane air conditioning. These cooling systems, which are usually considered in isolation, were compared in a comprehensive manner to get a full picture of their efficiency and effectiveness. The findings reveal that the implementation of cold aisle containment (CAC) or hot aisle containment (HAC) significantly improves air supply efficiency (ASE) and reduces the supply heat index (SHI), leading to a more uniform temperature distribution and enhanced cooling performance. Specifically, the ASE increased from 65.69% to 85.57% and 90.25% for underfloor precision air conditioning and from 71.29% to 92.16% and 92.17% for inter-column air conditioning, with corresponding reductions in SHI. The backplane cooling system offered consistent ambient temperatures throughout the room, eliminating thermal hotspots without the need for aisle containment. This study offers a comparative analysis of different airflow organization schemes, highlighting the benefits of aisle containment in precision and inter-column air conditioning and the suitability of backplane air conditioning for high-density cooling without the need for traditional aisle separation. The results are crucial for informing energy-efficient cooling strategies in data center design and operation. [ABSTRACT FROM AUTHOR]

Among all the operating parameters that control the cell culture environment inside bioreactors, appropriate mixing and aeration are crucial to ensure sufficient oxygen supply, homogeneous mixing, and CO 2 stripping. A model-based manufacturing facility fit approach was applied to define agitation and bottom air flow rates during the process scale-up from laboratory to manufacturing, of which computational fluid dynamics (CFD) was the core modeling tool. The realizable k -ε turbulent dispersed Eulerian gas-liquid flow model was established and validated using experimental values for the volumetric oxygen transfer coefficient (k L a). Model validation defined the process operating parameter ranges for application of the model, identified mixing issues (e.g., impeller flooding, dissolved oxygen gradients, etc.) and the impact of antifoam on k L a. Using the CFD simulation results as inputs to the models for oxygen demand, gas entrance velocity, and CO 2 stripping aided in the design of the agitation and bottom air flow rates needed to meet cellular oxygen demand, control CO 2 levels, mitigate risks for cell damage due to shear, foaming, as well as fire hazards due to high O 2 levels in the bioreactor gas outlet. The recommended operating conditions led to the completion of five manufacturing runs with a 100% success rate. This model-based approach achieved a seamless scale-up and reduced the required number of at-scale development batches, resulting in cost and time savings of a cell culture commercialization process. [Display omitted] • Appling a bioprocessing model package in manufacturing facility fit. • Predicting impeller flooding of a scale-up model by computational fluid dynamics. • Predicting pCO2 levels by CO 2 stripping model. • Evaluating cellular oxygen demand, foaming, and fire hazards. • Achieving seamless scale-up with reduced manufacturing scale development batches. [ABSTRACT FROM AUTHOR]

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

Fruit tree frost, an agricultural meteorological disaster primarily occurring in spring, severely impacts the growth and development of trees and fruit set. Therefore, exploring the temperature change rules of fruit trees during frost events is of considerable importance. This study used a T40 unmanned aerial vehicle (UAV) as the test vehicle based on the air disturbance frost prevention principle. The airflow field change pattern of the UAV was explored using the computational fluid dynamics simulation method, and the reliability of the multi-rotor UAV in frost prevention was verified using field tests. Setting the UAV height at 6.0 m above the ground and the rotor speed at 1000 r min−1, it was found that under the conditions of the inverse temperature phenomenon, the temperatures of different altitude layers will eventually converge to a stable value when the UAV down-rotating airflow is disturbed, which could be completed rapidly within 20 s. The results of the field test also showed that when the fruit trees reached the critical temperature of frost at the flowering stage, UAV intervention could have a substantial effect on the warming of the near-surface layers, whose warming amplitude was in the range of 2.5 °C–3 °C. This study provides a reliable method for mitigating frost, which serves as an important theoretical and guiding basis for improving agricultural frost disasters in China. • A multi-rotor UAV is used to test frost protection performance on fruit trees. • The temperature field characterizations are obtained. • The anti-frost effectiveness of UAV intervention is confirmed. [ABSTRACT FROM AUTHOR]

To meet the requirements of achieving higher efficiency and lower NOx pollution, the flame temperature in gas turbine combustors increases continually; thus, the effusion-cooling technology has been used to ensure the combustor liner remains within the allowed temperature, by which the combustion characteristics and emission behavior are possibly influenced. In order to investigate the effects of dome cooling air flow on combustion characteristics and NOx emissions, three-dimensional combustion simulations for a swirl-stabilized can-type gas turbine combustor are carried out in this work by using the computational fluid dynamics (CFD) method. Through adjusting the ratio of the dome cooling air flow and the dilution cooling air flow, the characteristics of flow field, temperature distribution and NOx emissions under each work condition are analyzed. At different ratios of the dome-cooling air flow to the total air flow, the flow velocity field in the region near the center of the combustion chamber is not changed much, while the velocity field near the chamber wall shows a more significant difference. The temperature in the outer recirculation zone within the combustion chamber is effectively reduced as the dome cooling air flow increases. By analyzing the distribution characteristics of the concentration of OH*, it is demonstrated that the dome cooling air flow does not have a direct effect on the reaction of combustion. It is also found that as the ratio of the dome cooling air flow to the total air flow increases from 0 to 0.15, the value of the NOx emissions drops from 28.4 to 26.3 ppmv, about a 7.4% decrease. The distribution of the NOx generation rate in the combustion chamber does not vary significantly with the increasing dome cooling air flow. Furthermore, by calculating the residence time in different stages, when the the ratio of the dome cooling air flow to the total air flow varies from 0 to 0.15, the residence time in the pilot stage decreases obviously, from 42 ms to 18 ms. This means that reduction in residence time is the main factor in the decrease of NOx emissions when the dome cooling air flow increases. [ABSTRACT FROM AUTHOR]

Pin fins have the potential to improve the thermal performance of various engineering devices. Modified pin fins could further increase their thermal performance in a passive way at lower cost. This study is aimed at numerically investigating the thermal performance of trenched hemispherical pin fins heat sink (THPFHS) and the influence of parameters including the trench number (N = 1, 3 and 5) and thickness (e = 1 to 5 mm). The simulations were performed using a computational fluid dynamics (CFD) software considering turbulent air flow conditions. Results showed that the use of aluminum fins fitted with one trench in the middle of the hemispherical pin fin considerably increased the local heat transfer. Furthermore, all studied configurations show high thermal performance factor (HTPF) compared with the conventional cylindrical pin fins heat sink (CPFHS). For this new configuration (THPFHS), Nu increases by 45% while the thermal resistance reduces by 42%, compared to the baseline case. On the other hand, this improved performance results in 50% pressure drop penalty. Moreover, the obtained results showed a significant improvement in the performance mainly at high Re. [ABSTRACT FROM AUTHOR]

Previous studies showed that opening windows could help with kitchen ventilation in pollutant removal. However, no studies have systematically examined the impacts of window positions on kitchen hood performance, and there is insufficient information on indoor airflow characteristics and pollutant distribution from makeup air through open windows. Therefore, the objective of this study was to use a validated computational fluid dynamics approach with CO2 as an indoor air quality indicator (a surrogate for cooking emissions) to understand the impacts of exhaust flow rate and the window opening position on the flow characteristics, concentration distribution, and capture efficiency (CE) of the hood. We conducted four-point validation tests of the numerical models based on CO2 concentration and temperature measurements under steady-state conditions. The validated models were subsequently used in simulations to understand the effects of six different window opening positions and the two exhaust flow rates on exposure. We found that the CO2 concentration could be better reduced by having windows open at the higher location. Generally, the front windows were more effective with CE > 80 % , followed by the back and the side windows, respectively. We also found that as the exhaust flow rate increased from 6.72 to 12.16 m3/min, CE reached >75% for all window positions, where the most significant increase was 1.58 times for the lower side window. To sum up, changing the relative position of the window and the exhaust hood could help disperse the incoming airflow from the window, improve the kitchen's overall ventilation, and reduce pollutant concentration. [ABSTRACT FROM AUTHOR]

Heat treatment is a common manufacturing process in the automotive industry used to produce high-performance metal components such as aluminum cylinder heads and steel gear sets. While a heat treatment schedule incorporating a quenching cycle, either through high-velocity air flow or immersion in liquids, can yield parts with durable mechanical properties, an unintended consequence of the intense quenching process is the introduction of thermal residual stress. This stress often is identified as a leading cause for quality issues related to high-cycle fatigue in aluminum engine components or geometric distortion in steel gear sets. Since thermal residual stress is caused by uneven cooling of the materials within the parts, an effective strategy for controlling thermal residual stress would involve directly managing the quenching processes. By reducing the temperature gradient inside the parts during quenching, the quality issues can be improved. Prior to the advent of computer simulation technology, the choice of quench media and the design of quenching recipes were often based on intuitive engineering judgment at best and trial-and-error iterative methods at worst. With the advancements in computational fluid dynamics (CFD) methodology, the quenching process can now be modeled through computer simulations for accurate calculation of temperature profiles and cooling histories of quenched parts. While CFD methods have the potential to manage quenching processes and mitigate thermal residual stress, it is important to note that CFD methods are not a one-size-fits-all solution for all quenching problems. Different quenching processes require different simulation strategies. Furthermore, CFD methods still require calibration and validation before they can be effectively utilized as virtual engineering tools, replacing traditional physical tryouts and experimental methods. The objective of this paper is to develop quenching simulation methodologies that can accommodate various heat treatment requirements and be used to optimize quenching processes, thereby managing quality concerns associated with thermal residual stress. While this research focuses only on two common quenching methods in engine component manufacturing, namely air quenching and water quenching for aluminum components, the principles and methodologies can be extended to other quenching methods based on convective motion of quenching media. Additionally, this research includes the parameterization and calibration of conjugate heat transfer models at the fluid-metal interface, which form the core of CFD simulation technologies. [ABSTRACT FROM AUTHOR]

The existing grape drying technology and equipment often have problems such as poor hygiene conditions, high drying costs, and large drug residues. Therefore, the market urgently needs grape drying equipment with low energy consumption, high efficiency, and a green-clean processing process. To solve the above problems, a piece of integrated drying equipment combining the two technologies of air impingement blanching and air impingement drying for multi-layer grape material drying is designed. The dried product quality is directly affected by the airflow field distribution. Therefore, obtaining good airflow distribution and airflow velocity uniformity in the drying chamber via parametric studies is essential to ensure uniform drying of products. Since parametric and optimization investigations by physical experiments are usually expensive and time-consuming, computational fluid dynamics (CFD) being a flexible and less expensive tool can be employed to perform such studies. In the current work, the airflow velocity distribution and uniformity of the drying material room are analyzed by Ansys Fluent software. The airflow velocity non-uniformity coefficient is used to evaluate airflow uniformity. Results show that the original design has poor uniformity and needs to be optimized. The influence of air inlet chamber deflection device and material truck airflow baffles on the flow field of the material drying room is investigated to improve the uniformity of airflow distribution. Considering drying efficiency and uniformity, drying material room structure with the addition of deflection device design with the structural parameters of L = 50 mm and θ = 76°, airflow baffle design with the structural parameters of h = 0 mm, θ2 = 20° is chosen as the final optimized design. After optimization, the velocity of airflow between material layers has improved overall, and the maximum difference of average airflow velocity between material layers has been reduced from 0.73 m/s to 0.69 m/s, improving the drying uniformity of dried materials. In comparison to other drying equipment, the current integrated drying equipment combing air impingement blanching and drying has the advantages of being efficient and energy-saving, suitable for large-scale drying of grapes with better drying quality. The current results could guide the drying equipment design for grapes and develop the grape drying industry with high-dried quality. [ABSTRACT FROM AUTHOR]

The microclimate environment can be conveniently controlled with accuracy by plant incubators, in which the cuttings propagation method can efficiently enhance seedling production. To ensure air flow evenly throughout the incubator, the scientific design of the air inlet is crucial. This study utilized a computational fluid dynamics (CFD) model to simulate the airflow patterns in a culture layer under different air inlet conditions. Furthermore, the optimal design parameters were determined by way of response surface methodology (RSM) and the Non-dominated Sorting Genetic Algorithm-II (NSGA-II). Adopting the optimal parameters, a prototype was manufactured, and a cuttings experiment was carried out with apple cuttings in the incubator. The results showed that the optimal air inlet radius is 90 mm, the optimal air inlet height is 188 mm, and the optimal uniform flow plate hole diameter is 13 mm. Meanwhile, the apple cuttings were able to root. Therefore, this incubator with optimal parameters can be used for cuttings. The study provides a methodological and theoretical basis for the future optimizing of air inlet parameters and promoting cuttings rooting. [ABSTRACT FROM AUTHOR]

This study compared computational fluid dynamic (CFD) model predictions on aerosol deposition in six asthmatic patients to the in-vivo results of the same group. Patient-specific ventilation and internal air distribution were prescribed using inspiratory and expiratory CT scans of each patient, accounting for individual lobar air flow distribution. Moreover, the significant influence of realistic mouth and throat geometries on regional deposition is demonstrated. The in-vivo data were obtained from single photon emission computed tomography (SPECT) in 6 subjects with mild asthma selected from a database of historical clinical trials. The governing flow and particle tracking equations were solved numerically using a commercial CFD tool, and the modeled deposition results were compared to the SPECT data. Good agreement was found between the CFD model, applying k-ω SST turbulence model, and SPECT in terms of aerosol deposition. The average difference for the lobar deposition obtained from CFD model and SPECT/CT data was 2.1%. The high level of agreement is due to applying patient specific airway geometries and inspiratory/expiratory CT images, anatomical upper airways, and realistic airway trees. The results of this study show that CFD is a powerful tool to simulate patient-specific deposition if correct boundary conditions are applied and can generate similar information obtained with functional imaging tools, such as SPECT. [ABSTRACT FROM AUTHOR]

This study proposes a mixed-mode dryer with a semi-transparent photovoltaic thermal (PVT) collector for the assessment of drying and thermal performance using computational and experimental findings. The thermal behavior and fluid flow characteristics have been analyzed to optimize the air flow rate in the PVT solar dryer by considering three different inlet velocities of 0.048 m/s (Case 1), 0.096 m/s (Case 2), and 0.144 m/s (Case 3). The temperature distribution is obtained more uniformly for the PVT collector and dryer cabin in Case 2. The results of the investigation show that Case 3 has a positive impact on the PVT solar dryer performance. In numerical and experimental methods, the enhanced thermal efficiency is attained as 30.78% and 29.78% for Case 2, and 33.20% and 31.14% for Case 3, respectively, in comparison to Case 1. Case 3 has improved Reynolds and Nussselt numbers by 3.06 and 2.45 times, respectively compared to Case 1. Experimental results varied by 2.24 to 4.90% from simulated outcomes obtained from CFD. The machine learning approach of ANN has been implemented with different hidden layers network models to choose the best drying conditions by predicting the drying performance parameters. [Display omitted] [ABSTRACT FROM AUTHOR]

Computational rhinology is a specialized branch of biomechanics leveraging engineering techniques for mathematical modelling and simulation to complement the medical field of rhinology. Computational rhinology has already contributed significantly to advancing our understanding of the nasal function, including airflow patterns, mucosal cooling, particle deposition, and drug delivery, and is foreseen as a crucial element in, e.g., the development of virtual surgery as a clinical, patient-specific decision support tool. The current paper delves into the field of computational rhinology from a nasal airflow perspective, highlighting the use of computational fluid dynamics to enhance diagnostics and treatment of breathing disorders. This paper consists of three distinct parts—an introduction to and review of the field of computational rhinology, a review of the published literature on in vitro and in silico studies of nasal airflow, and the presentation and analysis of previously unpublished high-fidelity CFD simulation data of in silico rhinomanometry. While the two first parts of this paper summarize the current status and challenges in the application of computational tools in rhinology, the last part addresses the gross disagreement commonly observed when comparing in silico and in vivo rhinomanometry results. It is concluded that this discrepancy cannot readily be explained by CFD model deficiencies caused by poor choice of turbulence model, insufficient spatial or temporal resolution, or neglecting transient effects. Hence, alternative explanations such as nasal cavity compliance or drag effects due to nasal hair should be investigated. [ABSTRACT FROM AUTHOR]

• Terrestrial laser scanning of the column of Hera Lacinia Temple and its surroundings. • Polygonal modelling and survey of the column and basement. • CFD analysis of the column, subjected to the main winds in the area. The study presents the results of a multidisciplinary research that integrates terrestrial laser scanning (TLS) and computational fluid dynamics (CFD) to document and analyse an archaeological asset subject to natural hazards. The experimentation was conducted on the surviving column of the temple of Hera Lacinia, located in Capo Colonna near Crotone (Italy). The column, the fragments of the crepidoma and of the foundation constitute the most visible remains of the peripteral Doric temple (second quarter of the 5th century B.C.), belonging to the most important sanctuary of Magna Graecia. The temple, the sanctuary and the other ancient buildings, which are in the area of the Capo Colonna promontory, were destroyed over the centuries to obtain construction material. Today the column and the remains of the temple are located inside the National Archaeological Park of Capo Colonna, protected from human action, but subject to natural phenomena which are dangerous or potentially dangerous in the long term. The wind exerts a constant erosion of the surface of the column and wear of the lower part of the shaft due to the continuous oscillations to which it is subjected; moreover, the wind thrust could add up to a possible seismic action. On the other hand, the geomorphological evolution of the promontory (coastal erosion and subsidence) causes the coastline to recede, and is responsible for landslides affecting the column-basement system. Starting from the point cloud acquired by the TLS, a mesh of the column, basement and surrounding terrain was created, aimed both at documentation, graphic analysis and CFD. The survey enabled the description of the current state of the column-basement system, documenting and measuring the shapes of the column, as well as the different inclinations of the individual parts caused by instability of the ground. Furthermore, the CFD model of the Hera Lacinia column was developed. The model is based on the three-dimensional Reynolds-Averaged Navier-Stokes (RANS) equations with the k-ε closure turbulence model. The oncoming wind was modelled according to the results obtained from 70 years of statistics analysis (from 1950–2021) of wind hourly data (streamwise and spanwise components). The interaction between wind flow and the Hera Lacinia column geometry shows very complex phenomenona. The adopted numerical model was able to simulate correctly the main phenomena involved such as the flow separation occurring around the column as well as the wake behind it. Particular attention was paid to investigating the most damaged areas of the column, identified by analysing recent images of the column, where the values of the time-averaged drag and lift forces were obtained. In order to obtain the erosion-based damage prediction future research will focus on the analysis of air flow erosion of the Hera-Lacinia column, starting from the measurements in situ of the main air characteristics and using the latter as the fluid for the numerical simulation, and by also considering different values of wind speed and directions. [ABSTRACT FROM AUTHOR]

One of the critical steps in the root crop harvesting process is screening tubers from soil. However, low screening efficiency seriously hinders the rapid development of the root crop industry. Clarifying the tuber-soil mixture separation behaviour and establishing the connection between vibration, airflow parameters, and separation index (SI) is critical to increasing screening efficiency. Corydalis Yanhusuo is employed as the research object, and the three-dimensional scale distribution and mechanical properties of tubers and soil particles are first counted. Then, a vibration and airflow coupling separation model of the tuber-soil mixture was constructed using the computational fluid dynamics and discrete element method (CFD-DEM) coupling method, and the physical parameters in the model were calibrated. A new method for calculating the SI is proposed. The relationship between vibration amplitude, frequency, airflow velocity, SI , and separation velocity was analysed. Simultaneously, the porosity change in the particle group during the separation process was investigated, and the relationship between vibration, frequency, and airflow velocity on the separation dynamics of binary mixtures was revealed by utilising data visualisation and frequency domain analysis. The platform for the vibration and airflow separation physical test was built. The separation behaviour of mixed particles in various parameters was discussed, as was the feasibility and accuracy of the numerical simulation results. The results of this study can provide theoretical support for the efficient screening of tuber-soil mixtures and further promote the rapid development of the root industry. [Display omitted] • The separation mechanism of binary mixtures with similar size distribution. • A new calculation method for the separation index. • Analysis of frequency domain of porosity change of particle group. • The quadratic interactive model of separation velocity. [ABSTRACT FROM AUTHOR]

Agricultural centrifugal fans play a pivotal role in agricultural machinery, particularly in the context of combine harvesters. The performance of these fans significantly impacts the overall operational efficiency of the machine. Given the absence of robust performance testing and evaluation methodologies for agricultural centrifugal fans, this study assesses fan performance by examining the actual air–flow dynamics in a certain space at its outlet. Subsequently, the effects of various structural parameters on airflow smoothness and attenuation are investigated by computational fluid dynamics simulation analysis. The optimal detection air duct is developed, and the measured fan performance parameters and evaluation indexes are discussed and analysed using bench tests. The obtained results indicate that the arc connection section exhibits reduced interference with the air outlet of the agricultural centrifugal fan. Additionally, the attenuation section, characterised by a diffusion angle of 4°, effectively captures air attenuation properties. Minimal wind speed fluctuation is observed at the measuring point equidistant from the inlet and outlet of the steady flow section. Consequently, optimised structural parameters for the detection air duct and the specified location of the measuring point are determined. Furthermore, the performance parameters of the agricultural centrifugal fan are measured, and dimensional and dimensionless performance evaluation curves are generated based on bench testing. The fan's efficiency increases with higher air volume and flow coefficient but tends to change gradually due to the rate of increase, aligning with the expected performance of the agricultural centrifugal fan. The proposed performance detection device and evaluation method for agricultural cleaning can accurately detect the operational performance of the agricultural centrifugal fan. • A detection air duct for agricultural cleaning fans has been designed. • The variation and attenuation characteristics of airflow in air duct were obtained. • A parameter detection system for agricultural centrifugal fan was developed. • The measured performance parameters of the fan were visualised and evaluated. [ABSTRACT FROM AUTHOR]