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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]

At present, air handling units are usually used indoors to improve the indoor environment quality. However, while introducing fresh air to improve air quality, air velocity has a certain impact on the occupants' thermal comfort. Therefore, it is necessary to explore the optimization of air-fluid-body interaction dynamics. In this study, the indoor air flow was changed by changing the opening and closing degree of the blower, and the thermal manikin is introduced to objectively evaluate the human thermal comfort under different air velocities. The main experimental results show that the air change rate increases with the increase of the opening and closing degree of the blower considering an ACH (air changes per hour) range between 3.8 and 10. For a better prediction, a linear correlation with a coefficient of 0.995 is proposed. As the blower's opening is adjusted to 20%, 25%, 30%, 35%, and 40%, the air velocity sensor positioned directly beneath the air inlet records average velocities of 0.19, 0.20, 0.21, 0.28, and 0.34 m/s over four hours, respectively. Observations on thermal comfort and the average sensation experienced by individuals indicate an initial increase followed by a decline when the blower's operation begins, with optimal conditions achieved at a 35% opening. These findings offer valuable insights for future indoor air ventilation and heat transfer design strategies. [ABSTRACT FROM AUTHOR]

In order to elucidate the impact of pressurized tubes' structures on the sowing performance of pneumatic seed delivery systems, the EDEM–CFD coupled simulation method was employed to analyze the influence of pressurized tube parameters, including length (L), corrugation depth (S), corrugation width (K), and the number of corrugations, on seed movement characteristics, distribution uniformity, and airflow patterns. Simulation-validated experiments were conducted to study the impact of the optimal pressurized tube structure on seeding performance. The results indicate that pressurized tubes significantly enhance the uniformity coefficient of seed distribution, reduce seed velocity, and decrease the coefficient of variation in distribution uniformity. When pressurized tube parameters, specifically length (L), corrugation depth (S), corrugation width (K), and the number of corrugations, are set at 800 mm, 8 mm, 50 mm, and 6, respectively, the uniformity coefficient of seed distribution exceeds 95%, and the coefficient of variation in seed discharge consistency for each row is less than 3.2%. Moreover, the seed velocity at the outlet of the pressurized tube, the relative velocity of two-phase flow, and pressure loss are all minimal, indicating superior seeding performance. This research provides valuable insights into the analysis of seed movement characteristics within pressurized tubes and the optimization of their structural parameters. [ABSTRACT FROM AUTHOR]

The roughness geometry has been introduced to improve the rate of heat transfer in a solar air heater duct. In the current work, circular and triangular shape geometries are used as roughness elements in the rectangular channel to enhance the thermal performance of reversed flow solar air heater (RFSAH). The important parameters selected for the research are Reynolds number (Re = 5000-18,000 (5 values)), pitch ratio (P/e = 4-12 (5 values)), and height ratio (e/D = 0.0392-0.1571 (4 values)). A 2D-computational fluid dynamics (CFD) model was developed using ansys (fluent 2022r1), and simulation was performed using the (RNG) turbulence model and validated with one set of experimental results for smooth duct and previous research. The findings revealed that the highest value of heat transfer was augmented about 2.18 times and 2.35 times for circular and triangular roughness geometry, respectively, as compared to the smooth channel at a Reynolds number of 12,000. The thermohydraulic performance factor (TPF) is 1.58 and 1.7 at pitch ratios of 6 and 5 for circular and triangular roughness geometry respectively, at Re of 12,000. [ABSTRACT FROM AUTHOR]

In this paper, earth–air heat exchanger is examined to achieve better system operation to cool a building in the arid climate of Ouargla city (Algeria). A higher cooling power requires a big pipe size which increases the pressure losses. Based on fluid dynamics, a new approach is carried out to evaluate the air flow pressure losses that contribute to the determination of the required blower power. The mathematical model of governing equations set is presented, and its numerical solution is calculated using a Matlab program. The multi-objectives optimization between two opposite targets is adopted for achieving the compromise solutions between maximal efficiency and minimal system size. For a given cooling power, the resolution of the earth–air heat exchanger model is carried out using the weighting method to perform the bi-objective optimization. At each cooling power, Pareto curves are generated for plotting the optimal points of efficiency and lateral pipe area. Obtained results show that for a chosen cooling power range, the system operation must reach at least an efficiency of 35% but less than 90% to cover all the size-efficiency compromises. Also, the lateral pipe area must be at least 6.025 m2/kW to start with acceptable efficiency. On the hottest summer day, for 3.5 kW as cooling power, the pipe outlet temperature reaches about 26 °C at a relatively high pipe length of about 95 m. [ABSTRACT FROM AUTHOR]

Short‐range exposure to airborne virus‐laden respiratory droplets is an effective transmission route of respiratory diseases, as exemplified by Coronavirus Disease 2019 (COVID‐19). In order to assess the risks associated with this pathway in daily‐life settings involving tens to hundreds of individuals, the chasm needs to be bridged between fluid dynamical simulations and population‐scale epidemiological models. This is achieved by simulating droplet trajectories at the microscale in numerous ambient flows, coarse‐graining their results into spatio‐temporal maps of viral concentration around the emitter, and coupling these maps to field‐data about pedestrian crowds in different scenarios (streets, train stations, markets, queues, and street cafés). At the individual scale, the results highlight the paramount importance of the velocity of the ambient air flow relative to the emitter's motion. This aerodynamic effect, which disperses infectious aerosols, prevails over all other environmental variables. At the crowd's scale, the method yields a ranking of the scenarios by the risks of new infections, dominated by the street cafés and then the outdoor market. While the effect of light winds on the qualitative ranking is fairly marginal, even the most modest air flows dramatically lower the quantitative rates of new infections. [ABSTRACT FROM AUTHOR]

This paper deals with the development and validation of a unified internal flow model (UIF) for the prediction of fluid behaviour in a network of 3D floodable cells such as an internal ship compartment subdivisions. The UIF model is incorporated in a generic time-domain ship-motion simulation environment. The flow model uses cell-averaged fluid momentum to account for dynamic (inertia) effects in compartments. A compartment is typically given the size of a ship compartment on board. The fluid solver can keep track of the air pressure in and air flow through compartments under isothermal assumption. Simulation results are compared against experimental data from four different configurations: a single tank draining experiment, a two compartment down-flooding experiment, an oscillating water column experiment under pressure, and a transient flooding experiment with a cruise ship in calm water. The general validity of the UIF model is demonstrated through these four examples. The newly developed UIF model overcomes the shortcomings seen in the steady Bernoulli-based simulations. Its application leads to a more accurate prediction of the floodwater progression in the ship, and it captures the fluid dynamics seen in the oscillating water column device very well, which is not possible using the steady Bernoulli approach. The general applicability of the UIF solver for internal fluid response in maritime application is thereby demonstrated. The effect of the internal compartmentalisation of a cruise ship and the effect of viscous roll damping on the transient roll response is discussed. [ABSTRACT FROM AUTHOR]

Copyright of Electroplating & Finishing is the property of Electroplating & Finishing Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The ability to express diverse behaviors is a key requirement for most biological systems. Underpinning behavioral diversity in the natural world is the embodied interaction between the brain, body, and environment. Dynamical systems form the basis of embodied agents, and can express complex behavioral modalities without any conventional computation. While significant study has focused on designing dynamical systems agents with complex behaviors, for example, passive walking, there is still a limited understanding about how to drive diversity in the behavior of such systems. In this article, we present a novel hardware platform for studying the emergence of individual and collective behavioral diversity in a dynamical system. The platform is based on the so-called Bernoulli ball, an elegant fluid dynamics phenomenon in which spherical objects self-stabilize and hover in an airflow. We demonstrate how behavioral diversity can be induced in the case of a single hovering ball via modulation of the environment. We then show how more diverse behaviors are triggered by having multiple hovering balls in the same airflow. We discuss this in the context of embodied intelligence and open-ended evolution, suggesting that the system exhibits a rudimentary form of evolutionary dynamics in which balls compete for favorable regions of the environment and exhibit intrinsic "alive" and "dead" states based on their positions in or outside of the airflow. [ABSTRACT FROM AUTHOR]

This paper's numerical study, which applies the finite volume approach and SIMPLE algorithm, aims to dynamically analyze airflow through a channel with Z-obstacles. Three distinct models were used to place the Z-barriers inside the channel. According to Demartini et al.'s model (2004) and as depicted in example A from the present analysis, the first Z-barrier (fin) is attached to the top wall (heated) and the second (baffle) to the bottom wall (insulated). The Z-barriers, on the other hand, were positioned in the second model on the same wall (in-line arrangement), either on the top surface (two fins in example B) or on the bottom wall (two baffles in example C). With the help of these studies, fluid dynamics in solar air collectors with barriers will be better understood and designed. [ABSTRACT FROM AUTHOR]

• A dual-wavelength high-speed digital holographic tomography system is developed. • The object beams from six different angles are simultaneously recorded by a single camera. • High-speed 3-D visualization inside the fluid at 2,000 frames per second has been achieved. • It is possible to track high-voltage discharge trajectories in three dimensions. Understanding and visualizing the intricate dynamics of rapidly moving fluids poses a fundamental challenge in the field of fluid mechanics. In this study, we present an innovative dual-wavelength high-speed digital holographic tomography system, poised to drive progress in the field of fluid dynamics research. This system has been meticulously crafted to enable the three-dimensional (3-D) visualization of rapidly moving and irregularly shaped airflow. To accomplish this, the system incorporates two lasers emitting different wavelengths, which effectively minimizes interference terms caused by the object beams in the off-axis multiplexing technique. Within this configuration, a single high-speed camera simultaneously captures the hologram generated by the interference between the reference and object beams from six different angles. In our experiment, the proposed system was utilized to achieve 3-D visualization of asymmetric airflow resulting from the high-voltage breakdown of air, capturing data at a rapid rate of 2,000 frames per second. Consequently, we successfully tracked the 3-D trajectory of the air breakdown phenomenon during discharge. The proposed system not only offers the ability to visualize asymmetric airflow in three dimensions but also has significant implications for gaining deeper insights into the behavior of fluids in dynamic and high-speed situations. [ABSTRACT FROM AUTHOR]

Bird wings are frequently modelled in the aerodynamics literature under the assumption that they are static aerofoils. Air flows over real bird wings can violate this assumption, both because of the topology of the wing and the fact that real wings typically undergo flapping and twisting motions during flight. There are many computational and numerical studies of air flows on flapping bird’s wings at low Reynolds numbers, but relatively few experimental studies due to the difficulty of modelling a realistic flapping motion. In this article, the flow on a real flapping bird wing is visualised in a teaching demonstration using high-speed photography. It is found that the main features of the flow can be observed and that the demonstration is a teaching aid for assisting student understanding of principles of aerodynamics. The possibility of incorporating the demonstration into a standard teaching course is discussed, with relevant teaching objectives highlighted. In conclusion, it is recommended that the demonstration could be useful as part of a course on aerodynamics, with further follow-up demonstrations and studies suggested. [ABSTRACT FROM AUTHOR]

The focus of this work is on developing a nonlinear grey model for the laminar flow regime of carrier fluid across the flat plate collector. The trust region reflective algorithm was used to solve the nonlinear laminar flow problem and handle the sparse matrix. The stream function, dimensionless velocity, gradients of velocity components, carrier fluid temperature, and the absorber plate temperature were estimated for a flat plate collector operated with and without a circular chimney. Similarly, the same technique was adopted to determine a model for heat transfer across the absorber plate. The numerically obtained solution was also compared with the parameters obtained through the instrumental measurement. The relative tolerance was kept at 10−5 for the white and grey box solutions. The developed model was noticed to have a smaller deviation than the conventional analytical model to predict the experimental values. The slip condition was observed for the proposed scheme. The uncertainty in the temperature measurement through the proposed model varies from ±0.53 to ±1.47 K. The minimum absolute percentage error (MAPE) lies in the domain of 0.52–1.67% for the nonlinear grey model, whereas the linear grey model for measuring absorber plate temperature has a percentage error of 0.0011–0.02%. [ABSTRACT FROM AUTHOR]

Owing to the outbreak of COVID-19, researchers are exploring methods to prevent contact and non-contact infections that occur via multiple transmission routes. However, studies on preventing infections caused by droplet transmission in public transportation are insufficient. To prevent the spread of infectious diseases, a new ventilation system in railway vehicles must be developed. In this study, a novel vertical drop airflow (VDA) system is proposed to mitigate the effect of droplet transmission in a high-speed train cabin. The droplet transmission route and droplet fate are investigated using three-dimensional fluid dynamics simulations, performed employing the Eulerian–Lagrangian model. Additionally, a porous model is adopted to simulate the effect of close-fitting masks. The results indicate that 120 s after coughing, the decrease in the droplet number in the VDA system is 72.1% of that observed in the conventional system. Moreover, the VDA system effectively suppresses droplet transmission because the maximum droplet travel distances of the VDA systems are 49.9% to 67.0% of those of the conventional systems. Furthermore, the effect of reducing droplet transmission by wearing a close-fitting mask is confirmed in all systems. Thus, the decrease in both droplet number and droplet transmission area in train cabins validate that the proposed VDA system has an effective airflow design to prevent droplet infection. [ABSTRACT FROM AUTHOR]

BACKGROUND For several years, orbitally shaken cylindrical bioreactors (OSRs) have become a new approach for propagation of mammalian cells cultivated under suspension. With new commercial cell culture media available today, allowing exceptionally high cell densities, the identification of suitable operating conditions presents a special challenge. Balancing hydrodynamic stress and other factors in reactors, this is particularly true for gas transfer rates providing sufficient oxygen (O2) to cultures that can attain ten‐fold greater biomasses than just a decade ago. This challenge is more profound the larger the working volume of the reactor becomes. RESULT: For 10‐L working volume cylindrical OSRs, we established a computational fluid dynamics model to evaluate the impacts of different operational conditions. Both fluid velocity distributions and O2 transfer coefficients (kLa) were calculated for different filling volumes and shaking speeds. Also, hydrodynamic stress parameters were investigated considering the most critical working conditions. CONCLUSION: The fluid velocity decreased with larger working volumes and, as expected, was found to increase with higher shaking frequency. Gas transfer rates between 10 and 54 h−1 were found in working volumes from 2.5 to 10 L and under shaking frequencies from 100–160 rpm. Critically assessing the obtained data, with no liquid‐submerged gas supply, we conclude that an air flow into the head‐space of a disposable bag appears to be satisfactory under certain operating conditions to support the culture of the most sensitive mammalian or insect cell cultures towards high cell density, presently in fed‐batch cultures achieving ≤30 × 106 cells mL–1. Shear stress parameters were found to be exceptionally low. © 2021 Society of Chemical Industry (SCI). [ABSTRACT FROM AUTHOR]

The asymmetrical impact of hull-shaped bodies is quite common when a ship sails in oblique waves. In this paper, the impact hydrodynamics of a typical hull obliquely entering water are studied via drop tests. The influence of the bottom bulbous bow and inclination angle on the fluid flow and pressure characteristics are the main concerns. Some special fluid characteristics (jet flows and air cavities) are observed, and the mechanism of load characteristics (i.e., multiple peaks, negative pressure and high oscillations) is explored by combining the free surface characteristics. The existence of the bulbous bow causes obvious fluid separation and jet impact, and the separation degree and jet impact position are affected by the inclination angle. The influence of drop height on impact fluid dynamics is explored. Higher impact velocities result in more intense fluid flow and bubble breaking. The dimensionless pressure coefficient at different entry velocities is different because the affected air cavity flows near the bottom bulbous bow. These findings reveal the law of load and fluid characteristics of hull bodies under asymmetrical impact. • A series of oblique drop tests of a hull-shaped body is carried out to clarify the hydrodynamic impact characteristics. • Mechanism of fluid dynamic behaviors including flow separation, jet flow impact and air cavity is clarified. • Complete dataset (free surface and impact pressure) is provided to fill the gap of oblique water entry of hull-shaped bodies. • Influence of inclination angle and bottom appendage on the fluid dynamic behaviors and load characteristics is clarified. [ABSTRACT FROM AUTHOR]

Copyright of Electric Machines & Control / Dianji Yu Kongzhi Xuebao is the property of Electric Machines & Control and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

To improve the performance of wind sensors in the high velocity range, this paper proposes a wind measurement strategy for thermal wind velocity sensors that combines the constant power and constant temperature difference driving modes of the heating element. Based on the airflow distribution characteristics from fluid dynamics, sequential measurement and correction is proposed as a method of measuring wind direction. In addition, a wind velocity and direction measurement instrument was developed using the above-mentioned approaches. The test results showed that the proposed instrument can obtain large dynamic wind velocity measurements from 0 to 60 m/s. The wind velocity measurement accuracy was ±0.5 m/s in the common velocity range of 0–20 m/s and ±1 m/s in the high velocity range of 20–60 m/s. The wind direction accuracy was ±3° throughout the 360° range. The proposed approaches and instrument are not only practical but also capable of meeting the requirements of wide-range and large dynamic wind vector measurement applications. [ABSTRACT FROM AUTHOR]

Pulmonary lobectomy is the gold standard intervention for lung cancer removal and consists of the complete resection of the affected lung lobe, which, coupled with the re‐adaptation of the remaining thoracic structures, decreases the postoperative pulmonary function of the patient. Current clinical practice, based on spirometry and cardiopulmonary exercise tests, does not consider local changes, providing an average at‐the‐mouth estimation of residual functionality. Computational Fluid Dynamics (CFD) has proved a valuable solution to obtain quantitative and local information about airways airflow dynamics. A CFD investigation was performed on the airway tree of a left‐upper pulmonary lobectomy patient, to quantify the effects of the postoperative alterations. The patient‐specific bronchial models were reconstructed from pre‐ and postoperative CT scans. A parametric laryngeal model was merged to the geometries to account for physiological‐like inlet conditions. Numerical simulations were performed in Fluent. The postoperative configuration revealed fluid dynamic variations in terms of global velocity (+23%), wall pressure (+48%), and wall shear stress (+39%). Local flow disturbances emerged at the resection site: a high‐velocity peak of 4.92 m/s was found at the left‐lower lobe entrance, with a local increase of pressure at the suture zone (18 Pa). The magnitude of pressure and secondary flows increased in the trachea and flow dynamics variations were observed also in the contralateral lung, causing altered lobar ventilation. The results confirmed that CFD is a patient‐specific approach for a quantitative evaluation of fluid dynamics parameters and local ventilation providing additional information with respect to current clinical approaches. [ABSTRACT FROM AUTHOR]

In order to develop an effective treatment method and improve drug delivery in lung diseases, it is very important to examine the airflow and the transport of inhaled pharmaceutical or harmful particles in the acinar region of the lungs. In this study, the alveolar airflow and the effect of particles of different sizes on aerosol dynamics were numerically investigated on a respiratory bronchiole model surrounded by alveolar sacs in the acinar region of the human lung using computational fluid dynamics (CFD). Numerical simulations were made for multiple breathing periods and three different respiratory conditions (i.e, low, normal and heavy breathing). In each flow situation, aerosol particles with different diameters from the model entry to the computational domain were released and their trajectories were tracked numerically. The results showed that there was air and particle entry into the alveolar cavities due to the movable alveolar walls. It was determined that the recirculating flow structures occurring in the alveolus characterize the particle dynamics. According to the results, the amount of aerosol remaining in the model decreased with particle size and flow rate. It was also found that aerosol particles with a diameter of more than 7 µm deposited on the duct walls and the particles below 5 µm in the alveolar cavities. Consequently, this study provides the important physiological results regarding the behavior of inhaled pharmaceutical or harmful particles in the alveolar region. [ABSTRACT FROM AUTHOR]

Brazilian countryside has well‐defined dry seasons that are mainly characterized by low relative humidity. The warm, dry air provides a thermal cooling effect when it interacts with wet porous structures (psychrometric effect). Depending on temperature conditions and relative humidity, it is possible to achieve up to 18.0 K reduction in the temperature of the structure, caused by water evaporation. Thus, the objective of this study was to propose and numerically investigate a low cost and sustainable air conditioning system by combining the potential of warm, dry air and characteristics of the flow within cyclones covered with thin wet cotton fabric. A validated mathematical model was developed, and the numerical results indicate that the cyclonic‐psychrometric system can provide up to 7.0 K reduction in a 20.0 m2 room on a warm day (305.0 K) with low relative humidity (20.0%). Energy balances and technical estimates showed that the electric power consumed by the proposed system would represent only 19.8% of the power required by a conventional 18,000 Btu air conditioner to promote the same reduction of temperature. This energy‐saving would have a direct and positive impact on the budget of users, especially those with low income and that live in dry regions. [ABSTRACT FROM AUTHOR]

In order to correct the solar radiation error of relative humidity, the mainstream capacitive sounding humidity sensor HC103M2 is selected and investigated by simulation analysis and experimental verification. First, the basic theories for solar radiation error and sensor error itself are elaborated, and simulational and experimental platforms are introduced. The computational fluid dynamics (CFD) method is utilized to theoretically investigate the dry error of the humidity sensor caused by solar radiation heating, which is related to radiation intensity, altitude, and solar elevation angle as well as reflectivity, thickness, and shape of the shield. Then, in order to verify the accuracy of the simulation, an experimental platform including a humidity sensor and two temperature sensors to measure the solar radiation heating is built to analyze the relative error of humidity obtained by the CFD simulation and experiment. It is found that their maximum deviation is 3.30% and the average error is 1.94%, which indicates that the calculation using the CFD method is accurate and feasible. In order to easily and operationally predict the solar radiation heating of the humidity sensor, a back propagation (BP) neural network fusion algorithm based on three inputs of radiation intensity, air pressure, and solar elevation angle is proposed. Compared with the solar radiation heating obtained by CFD simulation, the maximum absolute error is about 0.2 K, and the relative error of humidity is about ±1.30%. Finally, a case of vertical humidity profile correction considering the temperature-sensitive error of HC103M2 is analyzed. The response time of sensor measurement and the airflow into the shield are discussed as well. The corrected results after taking solar radiation heating into account are more similar to those measured by RS92 and cryogenic frost point hygrometer (CFH). This result shows that the prediction model is accurate, which may be applied to correct the dry error and further improve the accuracy of humidity measurement. [ABSTRACT FROM AUTHOR]

When targeting large spaces, temperature distribution occurs due to air flow. Therefore, when evaluating the some state quantity values in large spaces using the single‐mass model, the evaluation values cannot be accurately evaluated. In our developed method, we analyze in advance flow distribution with high computational load and make contributed ratio of indoor climate (CRI). By using CRI for making air‐conditioning operation plan, the air conditioning power consumption and demand response (DR) amount can be quickly obtained. We also conducted an evaluation to compare the difference in these values between our developed method and using the single‐mass model. The air‐conditioning power consumption and DR amount of the developed method were smaller than those of the single‐mass model since it takes into account the temperature difference between upper and lower regions of space. It was also confirmed that the derived room temperature distribution by the CRI had an error within 1 °C compared with the evaluation using computer fluid dynamics (CFD). © 2021 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

The fluid dynamics analysis on industrial, mixed-flow grain dryers with fixed bed using computational techniques is necessary to assist the design of such equipment contributing to cost reduction in the dryer projects and agricultural drying operations that involve the production of grains in the world. This study presents a Computational Fluid Dynamic (CFD) solution for air flow analysis in an industrial dryer. The air flow at the inlet and outlet of the dryer was investigated using the k-ω SST turbulence model. The dryer region with soybean was considered as a laminar porous medium flow in the permanent and isothermal regime, having for the model a simplified geometry with the tower considered as a porous medium and the air inlet and outlet as a turbulent fluid domain. The flow was treated with a permanent and isothermal regime. Dryer flow and pressures were used according to design parameters. To validate the k-ω SST turbulence model, the velocity profile at the dryer inlet was obtained experimentally, which presented results with good agreement between the numerical and the experimental model. The model obtained satisfactory results of the computational validation of the air flow in the dryer with good convergence requiring a minimum of computational effort, being suitable for the simulation of industrial-scale dryers, as to its air flow through a tower, operating with fixed bed soybean in the steady and isothermal regime. [ABSTRACT FROM AUTHOR]

The interactions between the emission of Volatile Organic Compounds (VOCs) and airflow play a key role in determining indoor pollutant concentrations. In the framework of Indoor Air Quality (IAQ) prediction, numerical models based on fluid dynamics are useful tools to address typical cases and then make decisions to improve both public and occupational health. This requires an accurate description of VOC emission processes from building materials, products and furniture, taking into account the diffusion of VOCs into these materials instead of using constant surface emission rates. A predictive model combining Computational Fluid Dynamics (CFD) for airflow and kinetics modelling for VOC emissions is described. The validation of airflow and VOC transfer models is carried out by comparing experimental and simulation results into a 128 L ventilated experimental chamber. Our results show that the Reynolds-Averaged Navier Stokes (RANS) approach, together with a standard k-ω turbulence model, provide good agreement between numerical and experimental airflows regarding both air velocity and age of air profiles. The overall VOC dynamics is also reproduced by numerical simulation for the eight VOCs monitored. The predicted absolute VOC concentrations are in agreement with experimental data for acetone, formaldehyde, hexanal and terpenes. However, numerical simulations underestimate the concentration of pentanal, propanal, butanal, acetaldehyde, which is discussed in terms of representativeness of emission parameters. Our results highlight that CFD simulations combined with VOC emission kinetics modelling is a promising tool for IAQ prediction, but it requires further investigation to fully understand the observed behaviour for some VOCs. This finally demonstrates the crucial need of tracking various VOCs simultaneously in the framework of assessing an IAQ prediction model. [Display omitted] • A 3D numerical model for predicting indoor VOC dynamics is described. • VOC concentrations emitted from particleboard are monitored in a ventilated chamber. • Simulated airflows and VOC concentrations are compared to experimental ones. • The coupled CFD-mass transfer model can reproduce the overall dynamics of VOCs. • The need to track multiple VOCs for IAQ prediction studies is highlighted. [ABSTRACT FROM AUTHOR]

In recent years, the flow characteristics research of the interstage region in counter-rotating axial fans in terms of fluid dynamics has attracted much attention. Especially, the dynamic relationship between interstage pressure pulsation and blade vibration in counter-rotating axial fans has not yet been clarified. This paper performs the signal processing method of wavelet decomposition and reconstruction in time-frequency analysis process. Under different flow conditions, weak-coupling numerical simulation program is employed to analyze the fluid-structure coupling interaction between interstage pressure pulsations and blade vibrations in counter-rotating axial fans. The results indicate that the fluid-structure coupling interaction field in the interstage of counter-rotating axial fans mainly excites the first-order vibration of the second-stage blade. At the same time, the consistency between the pulsation frequency and the vibration frequency of the airflow reflects the good coupling property. Two stage blades cut the airflow to cause field changes and airflow pulsation, and then, airflow pulsation causes blades deformation and produces vibrations of the same frequency at the blade. The deformation of the blades, in turn, causes the flow field changes. Rotating stall, vortex movement and breakdown produced low-frequency airflow pulsation and vortex vibration of the blade. [ABSTRACT FROM AUTHOR]

In this paper, the flapping dynamics and wake flow characteristics in the nonlinear hysteresis region are investigated experimentally by immersing a cantilevered flexible plate in uniform airflow. The experimental results show that the flapping mode of a cantilevered flexible plate in hysteresis region will be transited from periodical traveling wave mode to limited cantilever-like mode with the variation of Reynolds number. The flapping mode will greatly influence the kinetic parameters of a flexible plate and also wake flow characteristics. The comparison of Strouhal number values between flapping flexible plate and animals further indicates that the fluid dynamics between passive flapping and active swimming is similar to the obtained optimal propulsive efficiency. Flow visualization reveals that the Karman vortex street appears, vanishes and coherent structures of turbulent flow arise behind the stable flexible plate with increasing Reynolds number. Meanwhile, the measurements of pressure distribution in wake flow provide a good physical understanding of the energy-saving mechanism and the optimal arrangement in fish school. Moreover, the fast Fourier transform (FFT) spectra of fluctuating velocity indicate that the characteristics of wake flow are closely related to the flapping mode of flexible plate. The wake flow will come into strong harmonic excitation state when flapping mode transits into a limited cantilever-like mode. [ABSTRACT FROM AUTHOR]

Insect pectinate antennae are very complex objects and studying how they capture pheromone is a challenging mass transfer problem. A few works have already been dedicated to this issue and we review their strengths and weaknesses. In all cases, a common approach is used: the antenna is split between its macro- and microstructure. Fluid dynamics aspects are solved at the highest level of the whole antenna first, that is, the macrostructure. Then, mass transfer is estimated at the scale of a single sensillum, that is, the microstructure. Another common characteristic is the modeling of sensilla by cylinders positioned transversal to the flow. Increasing efforts in faithfully modeling the geometry of the pectinate antenna and their orientation to the air flow are required to understand the major advantageous capture properties of these complex organs. Such a model would compare pectinate antennae to cylindrical ones and may help to understand why such forms of antennae evolved so many times among Lepidoptera and other insect orders. [ABSTRACT FROM AUTHOR]

The use of face masks for the general public has been suggested in literature as a means to decrease virus transmission during the global COVID-19 pandemic. However, literature findings indicate that most mask designs do not provide reliable protection. This paper investigates the hypothesis that the impaired protection is mainly due to imperfect fitting of the masks, so that airflow, which contains virus-transporting droplets, can leak through gaps into or out of the mask. The fluid dynamics of face masks are investigated via analytical and numerical computations. The results demonstrate that the flow can be satisfactorily predicted by simplified analytical 1D-flow models, by efficient 2D-flow simulations and by 3D-flow simulations. The present results show that already gap heights larger than 0.1mm can result in the mask not fulfilling FFP2 or FFP3 standards, and for gap heights of ca. 1mm most of the airflow and droplets may pass through the gap. The implications of these findings are discussed and improvements to existing mask designs are suggested. [ABSTRACT FROM AUTHOR]

An analysis of the airflow around an AeroDesign aircraft did perform to verify the turbulence generated by the propeller's high rotation and its possible propagation to the aircraft surfaces, which may impair its stability and control. The airflow behavior through the propeller and around the aircraft was verified using a computational tool to run the simulations. For this, it was considered two computational domains of unstructured tetrahedral mesh: a cylindrical for the propeller and a rectangular for the aircraft as a whole. The governing equations were solved using the standard k-epsilon and standard k-omega turbulence models. Later the results' convergence, it was observed that the streamlines around the aircraft were well behaved, despite the turbulence produced by the propeller's high rotation. The results did not affect the aircraft's overall moments according to its gravity center, consequently being able to validate the stability qualities of the analyzed aircraft. [ABSTRACT FROM AUTHOR]

A modified vortex spinning technology, which produces core-spun yarns by means of a tangentially injected swirling airflow, is of great prospect in view of its production rate and yarn structure. In this paper, a numerical study based on computational fluid dynamics is presented to investigate the characteristics of the flow field of this system. In the simulation, the effect of the rotating front rollers on the flow field is taken into consideration. Flow characteristics inside the spinning nozzle, flow field of the front rollers, and streamline patterns have been revealed. The results show that a high-speed swirling flow is generated in the near-wall region in the nozzle chamber due to the ejection of air-jets from the tangential injectors. An asymmetric sub-pressure zone is formed in the core region of the nozzle chamber where the interactions of the high-speed swirling flow and three streams of secondary flows generate three vortices. Airflows in the vicinity of the front rollers generally converge toward the nozzle entrance from all directions except those in the boundary layer of the front roller surfaces, which is helpful for the delivery of fibers into the nozzle. A vortex is formed above the top roller and another beneath the bottom roller. The results of the streamline patterns show that the flow characteristics of the modified vortex spinning can facilitate the formation process of the core-spun yarn, which presents a qualitative explanation to the dynamic behavior of the fibers that was experimentally obtained. [ABSTRACT FROM AUTHOR]

[Display omitted] • The effect of ambient airflow on particle dynamics and the mixing efficiency highly depends on particle size. • Medium particles may suffer from a negative airflow effect on the mixing efficiency. • A new mathematical-statistical method (POD-ANOVA) is used to elucidate air-driven mixing mechanisms. Numerical simulations by the discrete element method (DEM) and DEM-computational fluid dynamics (CFD) have greatly facilitated the investigation of mixing kinetics in various particle mixing systems, including the common container blender. Recently, airflow within the container blender has been found to remarkably improve the mixing efficiency of fine particles. Nevertheless, a wide range of particle sizes has not been examined regarding the airflow effect. Thus, to comprehensively understand the particle size dependence of the airflow impact on powder mixing, this study aims to investigate the relationship of various particle diameters and powder mixing in an industrial container blender. An advanced mathematical-statistical method, named proper orthogonal decomposition-analysis of variance (POD-ANOVA), is used to clarify the complex mixing mechanisms. Numerical results show that airflow has different impacts on the mixing efficiency determined by the particle size range. The mixing of coarse particles with diameters above 1.000 mm is not significantly influenced by airflow, whereas medium-sized particles, ranging from 0.5000 to 1.000 mm, display reduced mixing efficiency as particle size decreases. Conversely, for small particles (0.2000–0.5000 mm), the mixing efficiency improves when decreasing the particle size. The underlying variations of powder mixing mechanisms have been well elucidated, and the convection mixing mechanism is found to be crucial in determining the mixing efficiency via POD-ANOVA analysis. Consequently, this work provides critical insights into the airflow effect during powder mixing, which has been verified to be highly dependent on particle size and is dominated by the convection mechanism. [ABSTRACT FROM AUTHOR]

We introduce a novel modelling tool for the activated sludge process (ASP) based on large-eddy simulation and multiphase Eulerian–Lagrangian coupling. Aeration-driven sludge activation is a key part of wastewater treatment and represents the vast majority of its energy consumption. Our model allows interaction among the liquid (wastewater), solid (sludge) and gas (air bubbles) phases, to provide insight on the fluid dynamics taking place during ASP. The model uses an Eulerian–Lagrangian point-particle algorithm that respects the discrete nature of both sludge flocs and air bubbles. Four-way coupling is implemented, where the interaction between solid particles is handled by a soft-sphere collision model. The analysis was focused on quantifying the Oxygen transfer from gas to liquid to solid, i.e., the conditions for aerobic bacteria activation. Such transfer is complex due to the dispersed nature of the gas and solid phases and the turbulent mixing occurring in the tank. Unlike box-modelling approaches, our three-dimensional model describes the evolution in space and time of the concentrations of these species and the Oxygen exchange, without a priori assumptions on the nature of the mixture. The model was validated versus experimental data using the interphase exchange of Oxygen as the key parameter, exhibiting in all cases an excellent agreement with measurements that qualitatively improves Eulerian–Eulerian approaches in five different tests. Subsequently our model was used to simulate a realistic scenario within the aeration basin of a wastewater plant and explore its results across a wide parameter range (aerator distribution, dissolved Oxygen levels, air flow rate, sludge size, bubble size). This allow us the explore the time evolution of the activation process and therefore test its performance versus the air flow rate injected (hence, energy). Our results indicate that the initial dissolved Oxygen levels within the basin (related to weather conditions and aeration frequency) are critical for sludge activation, with initial anoxic conditions being very taxing. For a given flow rate, bubble screens (i.e, more aerators) provide significantly better performance. Finally, we compare model estimations of bacterial Oxygen uptake with field data obtained from real-life ASP in wastewater plants, finding a good agreement. We therefore present to the community a reliable and extendable model that solves the fluid mechanics and the basic eco-hydraulics of the three-phase system encountered in wastewater plants, with minimal empirical inputs. This is a valuable and precise tool to test the operations and design of ASP and similar processes. [Display omitted] [ABSTRACT FROM AUTHOR]

The spouted bed has a vigorous cyclic movement of the solids and high rates of heat and mass transfer, allowing for effective contact between the different phases. However, the spouted bed may exhibit instabilities for inherently cohesive solids due to unwanted agglomeration, preferential channels, particle segregation and high energy consumption. In this context, the present work analyzed the effect of a preliminary treatment of the orange waste, through the addition of lime and mechanical pressing, on the fluid dynamics in two spouted bed configurations of same dimensions, one conventional (CSB) and the other one modified with mechanical agitation (modified mechanically spouted bed, MMSB). The preliminary treatment of the biomass allowed reducing the moisture content by 31.7%, thereby improving the movement of solids in the CSB as when the in natura (raw) biomass was loaded, as the latter underwent agglomeration until it no longer circulated. Persistent instability issues in the CBS were overcome through mechanical stirrers, which made the bed uniform by improving the movement of solids in the annular region. Furthermore, mechanical agitation allowed increasing the maximum static bed height from 21.1 to 27.0 cm, as well decreasing the air flow by up to 91.74%, since the air stream is only that required for bed expansion. [Display omitted] • The complete pretreatment reduced the moisture content of the biomass by 31.7%. • The pretreatment was mandatory to the motion of particles in both configurations. • Mechanical stirring prevented the agglomeration of solids close the inner walls. • Movement of the biomass was made primarily by the rotation of the stirrer. • Stirring reduced minimum spout velocity by 91.74% and pressure drop by 18.1%. [ABSTRACT FROM AUTHOR]

Use of gas-liquid equilibrators to measure trace gases such as CO2, methane, and radon in water bodies is widespread. Such measurements are critical for understanding a variety of water quality issues such as acidification due to elevated CO2 or other processes related ecosystem metabolism and function. However, because gas-liquid equilibrators rely on generating sufficient surface area for gas exchange between liquid and gas phases, most traditional equilibrators pass water through small orifices or interstitial spaces that rapidly clog in highly productive or turbid waters, conditions that are common in estuaries, coastal bays, and riverine systems. Likewise, in cold temperatures, such equilibrators are subject to freezing. Both situations lead to failure and limit utility, especially for long term, continuous environmental monitoring. Here we describe and test a gas-liquid equilibrator that relies on a continuous falling film of water over a spherical surface to drive gas exchange. Our results demonstrate that this design is accurate in its ability to equilibrate fully to aqueous CO2 concentrations, is functional across a wide range of gas concentrations, and has a response time that is comparable with other equilibrator designs. Because this equilibrator uses free flowing, falling water to produce a surface for gas exchange, our field trials have shown it to be very resistant to clogging and freezing, and therefore well suited to long term deployment in highly productive waters like estuaries where CO2 concentrations fluctuate hourly, daily, and seasonally. When generated across a spherical surface, the falling film is not adversely affected by tilting off vertical, conditions that are common on a ship, small vessel, or buoy. [ABSTRACT FROM AUTHOR]

The mammalian olfactory bulb (OB) plays an essential role in odor processing during the perception of smell. Optical imaging of the OB has proven to be a key tool in elucidating the spatial odor mapping and temporal dynamics that underlie higher-order odor processing. Much is known about the activation of olfactory sensory neuron (OSN) glomerular responses in the dorsal olfactory bulb (dOB) during odor presentation. However, the dorsal bulb provides access to only approximately 25% of all glomeruli, and little is known about how the lateral bulb functions during this critical process. Here, we report, for the first time, simultaneous measurements of OSN glomerular activity from both the dOB and the lateral olfactory bulb (lOB), thus describing odor-specific spatial mapping and the temporal dynamics of olfactory input to both the dorsal and lateral bulb. Odor responses in the lateral bulb tended to be most prominent in the dorso-lateral (D-L) region. Lateral glomeruli became active in a dorso-ventral (D-V) sequence upon odor inhalation, unlike the anterio-posterior (A-P) activity wave typical of the dorsal glomeruli. Across the entire D-L bulb, the spatial organization of these dynamics can be explained neither by the purely mechanosensitive dynamics (to breathing clean air) nor by the response amplitudes across glomeruli. Instead, these dynamics can be explained by a combination of zonal receptor distributions, associated OB projections, and air flow paths across the epithelium upon inhalation. Remarkably, we also found that a subset of OSN glomeruli in the lOB was highly sensitive to extranasal air pressure changes, a response type that has not been reported in dorsal glomeruli. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this paper is to present applications of the topological optimization method dealing with fluid dynamic problems in two- and three dimensions. The main goal is to develop a tool package able to optimize topology in realistic devices (e.g. inlet manifolds) considering the non-linear terms on Navier–Stokes equations. Design/methodology/approach: Using an in-house Fortran code, a Galerkin stabilized finite element is implemented method to solve the three equation systems necessary for the topological optimization method: the direct problem, adjoint problem and topological derivative. The authors address the non-linearity in the equations using an iterative method. Different techniques to create holes into a two-dimensional discrete domain are analyzed. Findings: One technique to create holes produces more accurate and robust results. The authors present several examples of applications in two- and three-dimensional components, which highlight the potential of this method in the optimization of fluid components. Research limitations/implications: The authors contribute to the methodology and design in engineering. Practical implications: Engineering fluid flow systems are used in many different industrial applications, e.g. oil flow in pipes; air flow around an airplane wing; sailing submarines; blood flow in synthetic arteries; and thermal and fissure spreading problems. The aim of this work is to create an effective design tool for obtaining efficient engineering structures and devices. Originality/value: The authors contribute by creating an application of the method to design a tridimensional realistic device, which can be essayed experimentally. Particularly, the authors apply the design tool to an inlet manifold. [ABSTRACT FROM AUTHOR]

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Automotive manufacturers nowadays are constantly working on improving their internal combustion engines' performance by reducing the fuel consumption and emissions, without compromising the power generated. Manufacturers are therefore relying on virtual engine models that can be run on simulation software in order to reduce the amount of time and costs needed, in comparison with experiments done on engine test benches. One important element of the intake system of an internal combustion engine is the throttle valve, which defines the amount of air reaching the plenum before being drawn into the cylinders. This article discusses a widely used model for the estimation of air flow rate through the throttle valve in an internal combustion engine simulation. Experiments have been conducted on an isolated throttle valve test bench in order to understand the influence of different factors on the model's discharge coefficient. These experiments showed that the discharge coefficient varies with the pressure ratio across the throttle valve and with its angle. Furthermore, for each angle, this variation can be approximated with a linear model composed of two parameters: the slope and the Y-Intercept. These parameters are calibrated for different throttle valve angles. This calibration can be done using automotive manufacturers' standard engine test fields that are often available. This model is then introduced into an engine simulation model, and the results are compared to the experimental data of a turbocharged engine test bench for validation. They are also compared with a standard discharge coefficient model that varies only with the throttle valve angle. The results show that the new model for the discharge coefficient reduces mass flow estimation errors and allows expanding the applications of the throttle valve isentropic nozzle model. [ABSTRACT FROM AUTHOR]

Highlights • Effects of residual air bubbles on diesel spray dynamics are investigated. • Structure of the jet at the early stage of injection is analyzed. • Experimental and numerical approaches are employed to provide further insights. • The transparency of the liquid jet at the start of injection is discussed. Abstract Experimental and numerical analyses of the effect of residual air bubbles in a single-hole high-pressure diesel injector nozzle are presented. Detailed information on spray structures and dynamics near nozzle exit at the Start of Injection (SOI) is described. Experimental measurements are performed using a laser-based backlit imaging technique through a long distance microscope by injecting diesel fuel into a constant volume high-pressure spray chamber. Numerical investigation of, in and near-nozzle fluid dynamics is conducted in an Eulerian framework using a Volume of Fluid (VOF) interface capturing technique integrated with Large Eddy Simulation (LES) turbulence modelling. The present flow setup includes residual air bubbles remaining from a previous injection event, in-nozzle turbulence with no-slip wall conditions. Experimental images show a toroidal starting vortex near the nozzle exit suggesting a partially filled nozzle; transparency in the emerging jet demonstrates the presence of air trapped inside the nozzle liquid from the previous injection event. The numerical model provides insight into the influence of residual air bubbles on the spray morphology and dynamics of the emerging jet at the SOI. A mathematical code is developed to replicate the backlit imaging approach with the numerical results. The virtual images demonstrate a transparent liquid jet emerging into the pressurized chamber gas showing improved agreement with experimental images. The inclusion of air bubbles in the nozzle liquid prior to injection in the numerical model also yields improved agreement in the penetration velocity profile of the jet. These results explain how inclusion of residual air bubbles inside the nozzle liquid affects the physics of the penetrating jet at the SOI. The air bubbles inclusion also provides an explanation for the transparency of the emerging jet, rough interfacial surfaces, and enhanced necking behind the jet tip captured at the SOI. [ABSTRACT FROM AUTHOR]

Background and objective: The idiopathic interstitial pneumonias (IIPs) are diffuse parenchymal lung disorders that are associated with substantial morbidity and mortality. Early diagnosis and disease stratification of IIP patients are important because these are related with the treatment and prognosis. Idiopathic pulmonary fibrosis (IPF) and nonspecific interstitial pneumonia (NSIP) are two major distinctive pathologic patterns of pulmonary fibrosis. We researched the application of the fluid-structure interaction (FSI) to the respiratory system and compared the pulmonary acinus mechanics and functions in healthy and IIP models. Methods: The human pulmonary alveolus is idealized by a three-dimensional honeycomb-like geometry, and a fluid-structure interaction analysis is performed to study the normal and diseased breathing mechanics. The computational domain consists of two generations of alveolar ducts within the pulmonary acinus, with alveolar geometries approximated as closely packed 14-sided polygons. Findings: In a normal breathing cycle, the flow rate of the healthy model is significantly larger than that of the NSIP and IPF models. Similar trends are observed for the volume change and the maximum pressure drop. The flow rate and the volume change of the NSIP are almost the same as those of IPF. The maximum pressure drop of NSIP is 5.5% larger than that of IPF. There is a 47% decrease in the pulmonary acinus compliance for the NSIP and IPF compared with that of the healthy model. The acinus resistances of NSIP and IPF are higher than those of the healthy lung by 6.4~11.2%. In particular, the pulmonary acinus resistance of the NSIP lung is higher than that of the IPF lung by 4.5%. Conclusions: Our study demonstrates the differences of air flow and lung function in the pulmonary acinus between the healthy and the IIP models. These changes in the lung are important considerations for early diagnosis and disease stratification in patients. Patient-based geometry can to be included in the computational models in future studies. [ABSTRACT FROM AUTHOR]