Turbulent Air Flow Research Articles

Critical analysis of the energy and exergy performance of an air heater duct with perforated 60-degree V-down baffles affixed to the heated surface

The indirect-mode solar dryer, with a solar air heater as a vital component, is commonly preferred for enhancing agricultural product quality. Energy and exergy analyses for an air heating system assess thermal gain and irreversibility in energy conversion. According to the literature, the easiest way to enhance the SAH’s energy and exergy performance is by incorporating flow-modifying elements or turbulators in the air passage. And the effective-energy assessment accounts for the increased airflow pumping power demands. This work aims to experimentally compare the energy and exergy performance of a smooth air heater duct with one integrated with perforated V-shaped baffles while critically examining the factors leading to the efficiency variations. The racetrack-shaped perforated V-baffles with 60-degree air attack angles are installed on the heated surface with V-down and staggered hole arrays, covering a turbulent flow Reynolds number (Re) range of 5400–13,100 during experimentation. The investigation involves varying the pitch-to-duct depth ratio (p/H) of baffles (with values of 1, 2 and 3) and considering two different hole-aspect ratio (w/d) values of 5.04 and 2.68, with the same open area ratio. The results reveal that baffles with w/d of 2.68 at p/H of 3, causing enhanced airflow turbulence and momentum diffusivity, provide the highest effective-energy ([Formula: see text]) and exergy ([Formula: see text]) efficiencies values of 88.7% and 12.44%, respectively, at Re of 11,816 and 8765. Based on the operating and geometrical parameters used in the experiments, the correlations of [Formula: see text] and [Formula: see text] developed demonstrate good accuracy. The values for mean absolute error, root mean squared error and R 2 (coefficient of determination) in the correlations, developed using the statistical computing R software, are 0.012427, 0.014837 and 0.9913 for [Formula: see text] and 0.004332, 0.005047 and 0.9557 for [Formula: see text], respectively.

Benefit Through Vehicles Passing on Highways in Electrical Power Generation

The turbulent airflow caused by vehicular movement on highways is a source of kinetic energy for wind energy (WE) that can be utilized to power highway lighting and communications. The purpose of the current work is to design, install and measure the extent of benefit from small wind turbines along a Highway (HW) in one of the governorates of Iraq - Dohuk. In this investigation, wind speed measurements are close to a significant HW on the Dohuk-Zakho-Iraq (DZI) Road. The three positional characteristics are examined for the wind turbines' optimal position. These factors are heights above ground level, lateral distances from the road shoulder, and the wind turbines' highway-facing orientation. It is possible to supply electrical power for side lighting of external roads via vertical axis wind turbines (VAWT), which are produced from disturbances in air movement. In addition, a battery pack has been used to store energy to sustain fluctuations caused by stopped vehicle traffic and to ensure load operation in the event of a wind turbine stop. A 500W capacity vertical axis windmill is being worked on. The suggested landscaping technique has generated exceptional and long-lasting effects for a price of under 350 US dollars.

Impacts of inclined plate on melting time for phase change material filled blocks: Experimental and numerical analysis

This study investigates the impact of inclined plates on the melting time of phase change material (PCM)-filled blocks in a channel under turbulent airflow, considering different velocities. The primary objective is to analyse how inclined plates influence the melting process and the time required for complete melting of PCM blocks. Both experimental and numerical approaches are employed using the finite volume method to solve two-dimensional time-dependent governing equations. The Reynolds numbers are varied at 40000, 50000, and 60000, while the inclination angle of the plate ranges from α = 110° to 130°. RT25HC is selected as the PCM. The findings reveal that inclined plates effectively regulate PCM cube melting times within a block, influencing the flow field and temperature distribution in the channel. Notably, both experimental and numerical results consistently highlight the α = 110° inclination angle as the most effective among the considered angles.

A numerical simulation study on the distribution of cutting dust and airflow in a fully mechanized mine face based on rotating fluid theory

The turbulent airflow generated by the shearer's rotation has a significant impact on the spread of cutting dust. In this study, the actual shearer drum was used as a physical model, and the MRF method was applied to simulate coal cutting operations with consideration of rotating fluid, accurately reproducing the turbulent airflow generated during cutting. By comparing the different simulation results, it is found that: the wind flow under systematic ventilation is gentle and even, while the cut-off wind flow generated by "inlet" has a great impact on the coal mining area in terms of scope and degree, and the horizontal and vertical dispersion is very strong, with a large amount of wind flow shifting in the range of 17 m < x < 36 m, and the dust mass concentration increasing rapidly; When the MRF method is adopted, the wind flow disperses more gently, and the dust is shifted to the pavement within the ranges of 19 m < x < 25 m and 27 m < x < 36 m, which makes the dust distribution more uniform and continuous in space, and forms a dust belt with high concentration of about 10 m in length on the downwind side of the front drum, which is more in line with the production reality.

Effect of inhaled air temperature on mucus dynamics in the proximal airways

The aim of the present study is to understand the role of steam/cold-air inhalation on the mucus layer dynamics in the proximal airways. We model these flows as a viscoelastic liquid (lining the inner side of a tube) sheared by a turbulent airflow and subjected to a radial heat flow. The linear stability analysis of the resulting flow is carried out using numerical and thin-film approaches. The air–mucus interface tension, coupled with the azimuthal curvature, leads to the previously predicted axisymmetric capillary mode responsible for airway closure in distal airways. The viscoelasticity of the mucus leads to axisymmetric and new non-axisymmetric elastic modes, with the former possessing a higher growth rate. The axisymmetric elastic and capillary modes merge to give rise to a new ‘elasto-capillary mode’ possessing a growth rate nearly equal to the combined growth rate of the elastic and capillary modes. The analysis predicts a strong stabilising effect of the thermocapillarity induced by steam inhalation on the elasto-capillary mode. Thus steam decreases airway resistance, which could explain the observed therapeutic effect of steam inhalation. The opposite is the case when the inhaled air is colder than the body temperature, in agreement with the observations. The theoretical predictions are corroborated by the physical mechanism explaining the suppression/amplification of the elasto-capillary mode due to thermocapillarity.

Surgical smoke: a matter of hygiene, toxicology, and occupational health.

The use of devices for tissue dissection and hemostasis during surgery is almost unavoidable. Electrically powered devices such as electrocautery, ultrasonic and laser units produce surgical smoke containing more than a thousand different products of combustion. These include large amounts of carcinogenic, mutagenic and potentially teratogenic noxae. The smoke contains particles that range widely in size, even as small as 0.007 µm. Most of the particles (90%) in electrocautery smoke are ≤6.27 µm in size, but surgical masks cannot filter particles smaller than 5 µm. In this situation, 95% of the smoke particles which pass through the mask reach deep into the respiratory tract and frequently cause various symptoms, such as headache, dizziness, nausea, eye and respiratory tract irritation, weakness, and abdominal pain in the acute period. The smoke can transport bacteria and viruses that are mostly between 0.02 µm and 3 µm in size and there is a risk of contamination. Among these viruses, SARS-CoV-2, influenza virus, HIV, HPV, HBV must be considered. The smoke may also carry malignant cells. The long-term effects of the surgical smoke are always ignored, because causality can hardly be clarified in individual cases. The quantity of the smoke changes with the technique of the surgeon, the room ventilation system, the characteristics of the power device used, the energy level at which it is set, and the characteristics of the tissue processed. The surgical team is highly exposed to the smoke, with the surgeon experiencing the highest exposure. However, the severity of exposure differs according to certain factors, e.g., ventilation by laminar or turbulent mixed airflow or smoke evacuation system. In any case, the surgical smoke must be removed from the operation area. The most effective method is to collect the smoke from the source through an aspiration system and to evacuate it outside. Awareness and legal regulations in terms of hygiene, toxicology, as well as occupational health and safety should increase.

Performance analysis and effect of various material fin-perforations in a plate-finned heat exchanger

Finding increasingly efficient heat exchangers requires a critical task: the development of fin profiles for prolonged life of equipment. The present study uses numerical analysis for better plate-finned heat exchangers hydraulic and thermal performance. Fin patterns are used in the analysis to evaluate a four-tube in-line heat exchanger. The proposed approach involves use of simulation and numerical methods to solve the heat transfer problem on different materials and wind velocity data as boundary conditions for improved heat transfer. The Reynolds-Averaged Navier-Stokes (RANS) model will be used to correct the average turbulent air flow over finned tubes in three dimensions using the ANSYS-Fluent software. The evaluation plan compares the current findings with published Nusselt number empirical correlations for the justification. Finally, the presentation of a parametric study on the impact of fin perforation size and shape on different materials and the behaviour of fluid dynamics and heat transfer. Larger fin perforation sizes (circular, rectangle, rhombus, and ellipse shapes) are found to enhance the heat exchangers' overall PEC and thermal efficiency for sustainability of the thermal equipment. The comparison was made between non-perforated and perforated fin types. Ultimately, it was determined that the best option for plate fin heat exchangers is the circular type perforated fin. When compared to without perforated fins, the circular type perforated fin has a higher heat transfer coefficient. A circular perforated fin has high performance, and the rhombus type perforated fin has lower performance.

Reducing Drag by Optimizing the Underbody with Ride Height in Formula 1

This study investigates the aerodynamic interaction between wheel wakes and the underbody of Formula 1 cars, focusing on the effect of varying ride heights on drag reduction and ground effect optimization. With the reintroduction of ground effect principles in the 2022-2026 Formula 1 regulations, the potential for enhanced vehicle performance through improved aerodynamic design is significant. However, the efficiency of venturi tunnels, essential for generating effective downforce, is compromised by turbulent airflows produced by the wheels, known as wheel wakes. This research utilizes computational fluid dynamics (CFD) simulations to model these interactions at different ride heights, aiming to pinpoint optimal configurations that minimize aerodynamic drag while maximizing downforce. Initial findings suggest a delicate balance between ride height adjustment and tunnel geometry optimization, offering potential pathways to achieve aerodynamic efficiency in modern Formula 1 vehicles. This paper contributes to the evolving discourse on high-speed vehicle aerodynamics, providing insights that could inform future vehicle design and regulatory frameworks in motorsports.

Bio-inspired, sensitivity-enhanced, bi-directional airflow sensor for turbulence detection.

Detecting airflow turbulence precursors promptly is crucial for ensuring flight safety and control. The initial stages of turbulence involve small reverse flows with random velocities and directions, which are not easily detected by existing airflow sensors. In this study, we designed a bionic, sensitivity-enhanced, bi-directional airflow sensor (BSBA) by incorporating bio-inspired circular tip slits and enlarging the central part of the cruciform beam structure. The BSBA exhibits a rapid response time (24.1 ms), high sensitivity (1.36 mV m-1 s-1), consistent detection of forward and backward airflow (correlation coefficient of 0.9854), and a low airflow detection threshold (1 ml). With these features, the proposed sensor can rapidly and accurately measure slight variations in the oscillating airflow, flow field, and contact force. The BSBA also achieves transparent obstacle detection on a quadrotor, even in visually challenging environments, by capturing minute changes in the flow fields produced by the quadrotor when encountering obstacles. The sensor's high sensitivity, consistent bi-directional detection, and fast response give it significant potential for enhancing safety in aircraft control systems.

Le statut mono ou bi-phonématique des prénasales en Ulund

Monophonematic or Biphonematic Status of Prenasals in Ulund&#x0D; The manɟaku group is a linguistic group that so far includes 15 dialects: ucuur, uɟool, utufan, ubok, ubuj, ujang, uciban-ukan, usiis, uteer, useerar, ulëkës, ubo- mat, uñoob-utam, uyu and ulund. The ulund language of the manɟaku group is taken as a sample in this inquiry. Its speakers call each other the Balund. The latter are thought to be originated in Guinea Bissau, and their main area of concentration is in pəlund, from which the name of the language's speakers is derived. The Balund began migrating from Guinea Bissau to Senegal in colonial times, due to the abuse they suffered in Portuguese lands. They settled in the southern part of Senegal, notably in the Ziguinchor and Kolda regions. It should be noted that despite their distinguisehd Islamization, the Balund remain very attached to their language and are close to their ancient cults and traditions.Our knowledge of Ulund speech is fragmentary, focusing on specific aspects of the language such as the study of nominal classes, the study of the pronominal system, the study of the verb, etc. We note that there are no in- depth studies of the phonetic system, hence the motivation for the study of ulund complex consonants in this article. Consonants are articulations produced with a total or partial obstruction at any point in the vocal tract. Consonants are a highly heterogeneous set of sounds, both articulatory and acoustic. The type of constriction in the vocal tract distinguishes an occlusive consonant from a constrictive consonant. Occlusives are characterized by a silence resulting from the complete closure of the vocal tract (occlusion) at a well-defined point. The fricatives, among the constrictives, are characterized by aerodynamic frictional noises created by turbulent airflow at a point in the vocal tract, presenting a strong constriction at the place of articulation. The mi-nasals are combinations of oral consonants (occlusive or constrictive) + nasal consonants (consonant produced with the lowering of the soft palate).The question of the interpretation of prenasals in many languages, particularly African languages, has already been the subject of a multitude of analyses. This study, which is intended as a modest contribution, in no way claims to list all the specific features of the West Atlantic languages already studied. Our aim is rather to give an overview of what is already known in this field, focusing on the phonetic aspect, so that our young students, when describing a new language of the Niger Congo sub-group, are not obliged to invest a great deal of effort and time on questions which have already been dealt with and answered.

Numerical Analysis of Turbulent Air Flow Dynamics in a Rectangular Channel with Perforated Nozzle-Shaped Vertical Baffles

Numerical Analysis of Turbulent Air Flow Dynamics in a Rectangular Channel with Perforated Nozzle-Shaped Vertical Baffles

Review of peculiarities of using wind catchers in energy-saving ventilation systems

Natural ventilation plays an important role in ensuring comfortable living conditions. Wind catchers are part of this process and can provide the required ventilation rate for buildings. The performance of wind catchers depends on the relevant parameters, such as height, configuration, cross-sectional shape, number of inlets, speed of movement and variability of air movement direction. HVAC equipment is not only responsible for the largest portion of the total energy consumption within a building, but also for most indoor air quality problems. Vents, air ducts, and dirty filters are a suitable place for the growth of fungi and molds produced by organic dust, which contaminate the circulating air and cause significant pollution problems. This could be more critical given that we spend almost 90% of our time indoors during our lives and work. Improvements in ventilation and air conditioning systems therefore play an important role in increasing energy efficiency in buildings, providing a better indoor climate for occupants and, as a result, reducing the likelihood of health problems. The cooling process plays an important role in creating comfortable conditions for humans. One of the most well-known elements of a passive cooling system for buildings with no or minimal energy consumption is a wind catcher. The effective-ness of wind catchers is influenced by wind force and buoyancy, and knowledge of the size, shape, and position of the outlet will help to understand new ideas and technologies for their application in modern architecture. A well-known example of natural ventilation that improves indoor quality by reducing pollution and humidity by replacing stale air with fresh outside air is a wind catcher (or wind tower). Nowadays, wind catchers are widely used in the world, having advantages in densely populated urban areas and in areas with low wind speeds, significantly affecting the reduction of cooling loads and providing the required ventilation rate of buildings. At present, there are many types of wind traps that can be classified according to the number of inlets, cross-sectional shape, and number of levels. The number of internal partitions, as well as the size and location of the openings of the wind collector, significantly affect its ventilation characteristics, efficiency, air flow velocity and turbulence, and also divide the cross-section of the wind collector into smaller channels, increasing the strength of its structure and reducing sensitivity to different wind directions

NUMERICAL ANALYSIS OF COMPOUND PARABOLIC SOLAR COLLECTOR WITH TWO GLASS COVERS

In a compound parabolic solar collector, a glass cover is normally used for decreasing the rate of heat loss from the absorber. In this paper, a solar collector with two glass covers and a concentration ratio of 1.6 is simulated and examined for the purpose of higher performance. The distance between covers is 45 mm and the cavity of solar collector is filled with air. Due to the temperature gradient, the turbulent free convection airflow takes place inside the cavity. As the main aim, the effect of the second glass sheet on performance improvement is examined. Towards this end, the equations govern to the turbulent buoyant airflow in the collector’s cavity was numerically solved by the finite element method using the COMSOL Multiphysics software. Also the conduction equation is employed for temperature computation in the solid elements. Numerical findings demonstrate the effective role of the second glass sheet in decreasing the rate of heat loss from solar collectors and a more than 6% increase in the thermal efficiency of the studied test cases is found because of the second glass sheet. Comparison between the numerical findings of free convection airflow with experimental data shows good consistency.

Time-evolving Impact of Trees on Street Canyon Microclimate

Nowadays, cities are frequently exposed to heatwaves, worsening outdoor thermal comfort and increasing cooling energy demand in summer. Urban forestry is seen as one of the viable and preferable solutions to combat extreme heat events and urban heat island (UHI) in times of climate change. While many cities have initiated tree-planting programs in recent years, the evolving impact of trees on street microclimate, in a time span of up to several decades, remains unclear. This study focuses on the cooling effects of a common type of street trees, linden trees, in five age groups, i.e., 10-20, 20-30, 30-40, 40-60, and 60-100 years old, while the diversity of trees is present in nature, that is, various species and crown geometries, The leaf area index (LAI) and leaf area density (LAD) of linden trees vary nonlinearly as they grow, peaking at different ages. Computational fluid dynamics (CFD) simulations were performed for an idealized street canyon with linden trees of various age groups. Turbulent airflow, heat and moisture transport, shortwave and longwave radiation, shading, and transpiration were fully coupled and solved in OpenFOAM. Meteorological data, including air temperature, wind speed, moisture, and shortwave radiation of the heatwave in Zurich (June 2019), were applied as boundary conditions. The results show that young trees in the age group of 10-20 years old provide little heat mitigation at the pedestrian level in an extreme heat event. Optimal heat mitigation by trees is observed for the group of 30-60 years old linden trees. Finally, the potential impact of growing trees on air ventilation in streets is evaluated.

Simplified models of aerosol collision and deposition for disease transmission

Fluid-mechanics research has focused primarily on droplets/aerosols being expelled from infected individuals and transmission of well-mixed aerosols indoors. However, aerosol collisions with susceptible hosts earlier in the spread, as well as aerosol deposition in the nasal cavity, have been relatively overlooked. In this paper, two simple fluid models are presented to gain a better understanding of the collision and deposition between a human and aerosols. The first model is based on the impact of turbulent diffusion coefficients and air flow in a room on the collisions between aerosols and humans. Infection rates can be determined based on factors such as air circulation and geometry as an infection zone expands from an infected host. The second model clarifies how aerosols of different sizes adhere to different parts of the respiratory tract. Based on the inhalation rate and the nasal cavity shape, the critical particle size and the deposition location can be determined. Our study offers simple fluid models to understand the effects of geometric factors and air flows on the aerosol transmission and deposition.

The Effect of Boundary Conditions on the Modeling of Anomalous Intensification of Turbulent Heat Transfer in an Inclined Groove in the Wall of a Narrow Channel

The effect of the boundary conditions of the first and second kind on the predicted characteristics of anomalous heat transfer intensification in the case of turbulent low-velocity air flow over an inclined groove in the hot wall of a narrow channel is numerically investigated. It is shown that the isothermality conditions lead to a considerable underestimation of the thermal efficiency of a surface structured with narrow grooves, compared with the conditions of heat flux constancy.

Development of the Corrected Force Analysis Technique in polar coordinates. Application on car window excited by a turbulent air flow

The identification of vibration sources is a subject that has already been widely studied and exploited by both the scientific community and the industries. The methods were initially intended for the identification of vibration sources on different structures like beam, plates and shells, but they are also used today for the characterization of materials or defect detection. This paper proposes an improvement of the corrected force analysis technique (CFAT) published several years ago and based on the force analysis technique (FAT). Inverse methods are redefined in the polar coordinates which are more suited to the problem of circular filtering. Polar inverse methods will be applied on the case of a car window excited by a turbulent flow by simulations and experiments.

Turbulent Airflows over Serrated Wings: A Review on Experimental and Numerical Analysis

The serrations on the blade's cutting edge and trailing edge are supposed to assist humans deal with noise, but the main idea is for research and use in nature. This research examines trailing edge extension hydrodynamics. Further, reducing the turbulent wake intensity behind the TE increases aerodynamic performance while leaving the static pressure distribution (as averaged across the span) substantially unaffected. Computational Aero-Acoustics simulates aerodynamic and acoustic reactions. This work discusses the experimental and computer simulations of turbulent flows. This paper provides the research to the technical community in the energy field (often non-specialists of turbulent flow investigations) with a summary of experimental and numerical techniques for investigating flows over a serrated wing, with a focus on the airfoil's self-noise generation mechanism and its main fields of application. The reader can use the given bibliography to determine the best method for the case of interest. This purpose means the individual tactics aren't discussed further. Given the breadth of acoustics, the experimental and numerical methods in this study can be used to forecast noise across serrated wings. It verifies that both strategies are still necessary, performing unique but complementary tasks.

Analysis of the effect of dust barriers on particulate matter dispersion from a construction site using CFD simulation

Urban construction activities generate particulate matter (PM), which poses a severe threat to urban residents' quality of life. The complex topography of urban areas and turbulent air flow make it difficult to predict PM dispersion and establish control measures. This study predicted PM dispersion from construction sites to urban areas under four wind directions using CFD simulations and determined optimal dust barrier heights for reducing PM exposure. This study showed that PM exposure on residents depends on wind directions in the urban area up to 2.3 times, still a flexible approach to determine optimal barrier heights based on stakeholder preferences was effective in all wind directions. Accurate PM dispersion predictions and control measures are crucial for improving urban air quality and residents' well-being.

Tackling the strange wind noise on a commercial building—Case study

A mysterious noise was reported in a commercial building. This commercial building consists of multiple levels of car parks with one single level of office space at the top. This top-level office area is home to Renault Australia, Mulgrave, Victoria. The office staff at the Renault reported a dreadful “howling” noise around the office. It sounded like a huge truck thundering past the office, especially on windy days. Specialist engineers, acoustic and wind engineers, were summoned to investigate the root cause of this noise. The initial investigation revealed that on windy days, the exterior aluminium Z Perlin profile cladding created air turbulences, which resulted in this unwanted noise. After conducting tests in the Monash University wind tunnel, various recommendations were suggested and trialled. For example, removing some purlins to reduce the air-flow turbulence, attaching fibre cement sheets to seal the purlins, vibration damping treatment of the Z purling cladding, and absorptive infill on the metal purlins. This case study presents the analysis of the noise, the results of the various tests and the successful practical resolution.