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Copyright of Study on Optical Communications / Guangtongxin Yanjiu is the property of Study on Optical Communications 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.)

【Objective】In order to study the temperature distribution and airflow requirements of high-speed optical modules, aiming to optimize the heat dissipation design and ensure the stable operation of optical modules.【Methods】The article adopts Flotherm simulation analysis to establish the numerical wind tunnel model of the optical module. The temperature distribution of each component during normal operation is obtained. The working air flow of the fan is also obtained when the system is stabilized, which are in line with the heat dissipation requirements in the specification of Multi-Source Agreement (MSA). In order to facilitate the testing and installation, the ”L” type wind tunnel fixture is designed. The actual surface temperature of each chip and the actual working wind flow rate of the wind tunnel are tested experimentally to verify the accuracy of the simulation results.【Results】The results show that in the case of the maximum temperature of 70 ℃, for the surface temperature of each chip, the difference between the simulation and the measured temperature is less than 2 ℃, with an error of less than 5%. For the airflow rate required for the heat dissipation of the entire optical module, the difference between the simulation and measured results is 0.2 Cubic Feet per Minute (CFM), with an error within 7%.【Conclusion】It can be shown that the simulation and measurement methods are feasible and the error is small, which provides an important reference value in the design and testing of heat dissipation of high-speed optical modules.

Coastal cities are vulnerable areas to the impacts of strong wind under typhoon events. To anticipate the impact, this study proposes a novel approach to integrate the typhoon track predictions generated by an ensemble k-Nearest Neighbors (k-NN) as the reference locations of the typhoon center. The global weather forecast data corrected using an ensemble k-NN-based typhoon track was transferred to the OpenFOAM model simulation to obtain the urban-scale wind with multiple obstacles. The Gwangan Bridge, which faces the East Sea and is one of the sites in Busan City used in this study, is used for evaluating the approach with three typhoon events, i.e. Nari in 2007, Chaba in 2016, and Cimaron in 2018. The simulation results are disseminated in a 3D web application framework using Node JS for the web framework, PostgreSQL and PostGIS for database management, and CesiumJS for the main JavaScript library of 3D visualization. The study results show that this approach can performed well when compared with observed data from the wind station on the bridge, with correlation coefficient, mean absolute error (MAE), and root mean square error (RMSE) of 0.902, 1.505, and 1.927, respectively. The adjustment of grid positions through an ensemble k-NN-based typhoon prediction model on the global weather forecast data for OpenFOAM input significantly contributes to the accuracy of urban-scale wind prediction. This study also produces a more sophisticated web-based virtual globe and 3D city model to demonstrate a current typhoon prediction and past typhoons, online simulation results of ensemble k-NN algorithm, a volumetric profile of typhoons, wind flow, streamlines, wind pressure around buildings and a bridge, warning status, and time series of predicted wind velocity for supporting the disaster early warning system.

The present study aims to investigate the role of vegetation in regulating pedestrian-level wind on Imam Street. Imam Street is one of the main streets of Tabriz city, and the wind speed at pedestrian level has made pedestrians feel uncomfortable, especially in the cold season. The method of the present study is descriptive-analytical research, in which numerical simulation was carried out to simulate wind flow for the current state and different proposed states using Dlubal RWIND 2.02 software. To this end, the effects of height, distance, and arrangement of vegetation (along with tree benches) (as the independent variables) on pedestrian-level wind speed (as the dependent variable) were investigated, and the relationships between the variables were examined using Spearman's correlation. The findings indicated that planting trees with a height of 6 meters, spaced at a distance of 3 meters according to density pattern 1, can enhance wind comfort on Imam Street by reducing the wind speed at the pedestrian level by 60%. The results showed that the use of vegetation compatible with the climate, at a given distance and according to a proper pattern, can significantly reduce wind speed. The surrounding tree benches direct the airflow towards the street and moderate the wind speed at the pedestrian level. [ABSTRACT FROM AUTHOR]

Copyright of International Journal of Architectural Engineering & Urban Planning is the property of Iran University of Science & Technology 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.)

Copyright of Przegląd Elektrotechniczny is the property of Przeglad Elektrotechniczny 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 research focused on simulating wind patterns in urban planning design offers substantial contributions to both the social and economic aspects of the urban planning and design field. To begin with, it addresses a critical factor in urban development, especially in Mediterranean climates, where natural ventilation significantly influences summer comfort. By incorporating predictive numerical simulations of urban wind patterns, this study provides valuable insights into improving outdoor thermal comfort within urban areas. This holds particular importance in the context of adapting to climate change, as it equips urban planners and architects with informed decision-making tools to create more sustainable and comfortable urban environments. Additionally, this research makes an economic contribution by presenting guidelines for iterative wind simulations in the early stages of designing medium-scale urban projects. Through the validation of a simulation workflow, it streamlines the design process, potentially reducing the time and resources required for urban planning and architectural design. This enhanced efficiency can result in cost savings during project development. Moreover, the study's recommendations concerning simulation parameters, such as wind tunnel cell size and refinement levels, offer practical insights for optimizing simulation processes, potentially lowering computational expenses and improving the overall economic viability of urban design projects. To summarize, this research effectively addresses climate-related challenges, benefiting both social well-being and economic efficiency in the field of urban planning and design, while also providing guidance for more efficient simulation-driven design procedures.

Surface ozone (O3) is influenced not only by anthropogenic emissions but also by meteorological factors, with wind direction being one of the most overlooked factors. Here, we combine the observational data of both O3 and wind flow to compare the variation in surface O3 with wind direction between coastal and inland regions of Fujian, a province in the southeast coast of China with complicated topography. We further conduct a numerical simulation using a global chemical transport model, GEOS-Chem, to interpret the observational results, explore the linkages between these O3 variations and wind flows, and identify the dominant processes for the occurrence of high O3 that varies with wind flows. The results from the observations over 2015–2021 suggest that, over coastal regions, surface O3 concentrations show a strong dependence on wind flow changes. On average, during the daytime, when southeasterly winds prevail, the mean of O3 concentrations reaches 83.5 μg/m3, which is 5.0 μg/m3 higher than its baseline values (the mean O3 concentrations), while the northwesterly winds tend to reduce surface O3 by 6.4 μg/m3. The positive O3 anomalies with southeasterly wind are higher in the autumn and summer than in the spring and winter. During the nighttime, the onshore northeasterly winds are associated with enhanced O3 levels, likely due to the airmass containing less NO2, alleviating the titration effects. Over inland regions, however, surface O3 variations are less sensitive to wind flow changes. The GEOS-Chem simulations show that the prevailing southeasterly and southwesterly winds lead to the positive anomaly of chemical reactions of O3 over coastal regions, suggesting enhanced photochemical production rates. Furthermore, southeasterly winds also aid in transporting more O3 from the outer regions into the coastal regions of Fujian, which jointly results in elevated surface O3 when southeasterly winds dominates. When affected by wind flows in different directions, the chemical reaction and transport in the inland regions do not exhibit significant differences regarding their impact on O3. This could be one of the reasons for the difference in O3 distribution between coastal and inland regions. This study could help to deepen our understanding of O3 pollution and aid in providing an effective warning of high-O3 episodes. [ABSTRACT FROM AUTHOR]

The buildings can influence wind flow, while a better wind flow in a city will improve the air quality for the sustainable development of the urbanites. At present, Computational Fluid Dynamics (CFD) is commonly used for wind flow simulation. However, CFD simulation is able to focus only on a certain height of a building. Hence, the 3D building model Level of Details (LoD) plays a vital role in the simulation. As regards the 3D building model standard, CityGML standard provides different LoD such as LoD1.0, LoD1.1, LoD1.2, LoD1.3, LoD2.0, LoD2.1, LoD2.2, LoD2.3, LoD3.0, LoD3.1, LoD3.2 and LoD3.3. Thus, this study aimed to overcome this problem by determining the best 3D building model’s LOD for CFD wind movement simulation. This study ran CFD simulation experiments on each stated LoD using the same 3D model building. Several important points (locations) at the building were selected and analysed to obtain the best wind velocity analysis for the LoDs. Through such analysis, LoD3.1 was selected as the model that fulfils the minimum requirements to have the best CFD wind flow simulation. This research can help future planning of cities towards realizing sustainable city development by taking into account the factors affecting wind movement in the city.

Unplanned dense settlements in the development pay little attention to the technical aspects of the building and the environment, one of which is high humidity conditions and circulation pathways. Circulation in settlements can also function as wind circulation, which can affect natural ventilation, comfort, and the health of residents. This study uses a quantitative method with a descriptive approach to describe the relationship between the circulation width variable and the wind speed variable. The results of periodic field observations and measurements are then interpreted descriptively to determine the effect of circulation width on wind flow in densely populated settlements in Taman Sari, Bandung. The results showed that outdoor circulation close to open spaces had better wind speeds compared to areas far from open spaces.

This paper highlights the advancement in wind energy harvesting using piezoelectric materials to produce sustainable power generation. It is a highly encouraging, fascinating, and challenging method to capture energy from piezoelectric materials. The purpose of this research is to evaluate the principal characteristic groups that affect energy harvesting performance and to provide recommendations for further improvement. Piezoelectric energy harvesters (PEH) can provide electricity for low-power electronic devices, which additionally possess the potential to boost self-powered, autonomous devices. The objective of this article is to provide recommendations for wind energy harvester modeling techniques. After establishing the fundamental idea of Piezoelectric Wind Energy Harvesters (PWEHs), it is next examined how well these devices function structurally and where their research stands in relation to various phenomena, including vortex-induced vibration, flutter, and galloping. A cantilever beam connected with a tip body is the typical component of a galloping piezoelectric harvester for wind energy collection. Wind energy has been turned into mechanical vibrations and ultimately into electrical power via the flutter phenomena. Fluttering-based wind energy harvesters are a new technology that provides an effective replacement for conventional wind turbines. The future development trend for PWEHs has been anticipated. The most current developments in strategies and approaches for wind energy harvesting using piezoelectric materials are also discussed in this paper. First, this paper highlights various piezoelectric energy harvesting materials, then it shows various wind energy harvesters’ design. After that this paper displays various types of wind energy harvesters and their applications. Finally, it highlights some challenges, future development, and recommendations.

The research focused on simulating wind patterns in urban planning design offers substantial contributions to both the social and economic aspects of the urban planning and design field. To begin with, it addresses a critical factor in urban development, especially in Mediterranean climates, where natural ventilation significantly influences summer comfort. By incorporating predictive numerical simulations of urban wind patterns, this study provides valuable insights into improving outdoor thermal comfort within urban areas. This holds particular importance in the context of adapting to climate change, as it equips urban planners and architects with informed decision-making tools to create more sustainable and comfortable urban environments. Additionally, this research makes an economic contribution by presenting guidelines for iterative wind simulations in the early stages of designing medium-scale urban projects. Through the validation of a simulation workflow, it streamlines the design process, potentially reducing the time and resources required for urban planning and architectural design. This enhanced efficiency can result in cost savings during project development. Moreover, the study's recommendations concerning simulation parameters, such as wind tunnel cell size and refinement levels, offer practical insights for optimizing simulation processes, potentially lowering computational expenses and improving the overall economic viability of urban design projects. To summarize, this research effectively addresses climate-related challenges, benefiting both social well-being and economic efficiency in the field of urban planning and design, while also providing guidance for more efficient simulation-driven design procedures. [ABSTRACT FROM AUTHOR]

Excessive heat in the high-rise urban fabric has contributed to pedestrian and occupants' discomfort. Establishing wind circulation in space with an environmentally compatible and optimal configuration is necessary to improve comfort in this region. The study benefits from field measurements and experimental validation of CFD simulation to investigate the effective parameters that affect wind speed. The master plan has proposed decentralized and limited high-rise construction to prevent the horizontal growth of Babolsar city. Meanwhile, the demand for high-rise buildings is high in the city. Therefore, altitude density (height factor) is considered as a constant factor. The buildings' orientation and enclosure based on the passages' width have opposite reactions in the direction of the prevailing wind. The correlation between the orientation and the enclosure with the wind speed are the values of 0.504 and 0.2226 respectively, which have the highest correlation among other parameters. The changes have been made in the building orientation factor in the dominant wind direction by creating permeability as well as creating low enclosure in the paths and empty spaces perpendicular to the dominant wind (W’= 3W, E’ = 0.33E). These strategies have finally improved wind velocity and created wind circulation in urban block spaces. Finally, according to the data analysis for Climate compatible in humid areas and the optimal behavior of wind flow for proper urban ventilation, an improved layout for future developments will be presented.

In this paper, an Actuator Disk Model (ADM) was introduced into a commercial computational fluid dynamic software and used to simulate the wake effect of wind turbines in a wind field with complex terrain. Then, the influence of towers with difference height on wake flow and power generation can be studied, which is particularly important for the wind field design in complex terrain. The numerical results are verified by means of comparison with the measured data of Supervisory Control and Data Acquisition (SCADA). More detailed numerical results show that the optimization of the design of high and low hybrid towers with difference size wind turbines can not only make full use of the advantages of high wind speed at high altitudes, but also reasonably improve the wake flow generated by the front wind turbine and increase the power generation of the wind field. It is found that the power increment generated by the high–low hybrid towers arrangement is roughly inversely proportional to U00.877, when only evaluating the effect of tower height; moreover, if the rotor diameter is further increased, the power gain of the hybrid arrangement scheme is roughly inversely proportional to U01.167. The research provides a robust and practical numerical method for the design of wind field layout and the optimization of high and low hybrid towers.

Excessive heat in the high-rise urban fabric has contributed to pedestrian and occupants' discomfort. Establishing wind circulation in space with an environmentally compatible and optimal configuration is necessary to improve comfort in this region. The study benefits from field measurements and experimental validation of CFD simulation to investigate the effective parameters that affect wind speed. The master plan has proposed decentralized and limited high-rise construction to prevent the horizontal growth of Babolsar city. Meanwhile, the demand for high-rise buildings is high in the city. Therefore, altitude density (height factor) is considered as a constant factor. The buildings' orientation and enclosure based on the passages' width have opposite reactions in the direction of the prevailing wind. The correlation between the orientation and the enclosure with the wind speed are the values of 0.504 and 0.2226 respectively, which have the highest correlation among other parameters. The changes have been made in the building orientation factor in the dominant wind direction by creating permeability as well as creating low enclosure in the paths and empty spaces perpendicular to the dominant wind (W’= 3W, E’ = 0.33E). These strategies have finally improved wind velocity and created wind circulation in urban block spaces. Finally, according to the data analysis for Climate compatible in humid areas and the optimal behavior of wind flow for proper urban ventilation, an improved layout for future developments will be presented. [ABSTRACT FROM AUTHOR]

Grid-based sand-fixing protection barriers have been widely used to solve linear engineering problems in sandy areas. Their placement directly affects the combined change law of wind speed weakening and sand sediment in the sand barrier. It also affects the cost of sand control and the selected structure of the protection system. Therefore, quantifying the effect of different sand barriers is important. We installed nylon mesh checkerboard sand-fixing barriers of three heights and three sizes on the windward side of the highway in the Ulanbuhe Desert, China. By using anemometer and sand collecting instrument, through comparing and observing air flow changes, windproof efficiency, and sand sediment inside the sand barrier, it is found that height had more influence on the protective benefit of a sand barrier than did the mesh specification. The protective effect at the boundary of a sand barrier resulted from compound superposition. The model for calculating a suitable sand barrier protection width was affected by sand-driving wind speed, open field wind speed, sand barrier unit side length, height, and actual protection demand. Sand barriers of 1 × 1 m (It is the grid size of the mesh.) at 20-cm height, 1 × 1 m and 1.5 × 1.5-m at 30-cm height could be laid over a wide area. Different collocation patterns can be selected according to the dominant wind direction. The results can provide basic data and theoretical support for sand barrier protection system. [ABSTRACT FROM AUTHOR]

The variation in daily environmental conditions has a notable effect on the thermal performance of the electrical machines, especially power transformers. The objective of this paper is to see the effect of solar radiation and wind flow external to the outdoor operating power transformers. The research work in this field involves the development of computational thermal models based on conventional International Electro-technical Commission (IEC) loading guide using appropriate software tools in order to determine the hot spot temperature. These thermal models are then modified by incorporating the effect of solar radiation and wind flow. The proposed method is validated using the operational data gathered from a 500MVA power transformer located at 400kV Grid Substation, Kankani, Jodhpur (Rajasthan, India). The comparative study between the conventional and modified thermal models helps in the reliable operation of power transformer and optimizes the use of forced cooling arrangements. [ABSTRACT FROM AUTHOR]

This article deals with the investigation of wind effects on a façade of a rectangular residential building with explicit modelling of the windows for specific wind conditions. The external wind pressure coefficients were treated on the façade and at the places of the window sills, linings, and lintel for the direction of the wind from 0° to 90° with increments of 22.5°. For a detailed analysis, the CFD simulation using Ansys Fluent was used. The method selected for the CFD simulation solution and its setting (quality of meshing, horizontal homogeneity of the boundary layer, etc.) were verified by known results of similar objects. The purpose of this analysis is to show how important it is to consider wind effects to determine the suitable placement of passive ventilation devices. Research shows the potential optimal position of ventilation units in terms of favourable pressure distribution. Zones with negative pressure and corners or façades in a wake are not suitable for applying passive ventilation units. The results can serve as a basis for designers to achieve optimal comfort in residential buildings. [ABSTRACT FROM AUTHOR]

In the framework of the wind energy network for distributed generation in urban environments for most South American countries, wind resource assessment studies have been carried out in activities to establish a suitable methodology to assess the wind potential in urban environments. Some methodologies are already published in research studies, and the wind tunnel is the most accurate solution to obtain insight into the wind resource when measurements are unavailable, which is the most frequent case. Nevertheless, besides its validity, one cannot disregard the high cost of producing a scaled urban model and access to a wind tunnel. In this sense, this paper compares results from a wind tunnel experiment and different numerical modeling approaches. Two commercial models (WindSim and Wasp Engineering) and one open-source CFD code (OpenFOAM) are used. The results from the modeling simulation concluded that CFD models could achieve lower deviations for the mean wind speed and turbulence intensity when compared with non-CFD models. With such results, CFD modeling is a promising tool for reliably evaluating wind potential in urban environments. [ABSTRACT FROM AUTHOR]

Wind energy harnessing in built environment contributes to the development of sustainable cities. In this study, flow features and wind energy over roofs with various parapet heights were investigated via computational fluid dynamics simulations. Effects of normalized parapet height (h p / H = 0, 1/320, 1/160, 3/320, and 1/80) and wind angle θ were examined. Moreover, flow features and associated aerodynamic mechanisms were investigated. Effect of h p / H on flow features and wind energy potential depended on roof locations and θ. Parapets had the greatest effect on velocity and turbulence intensity at θ = 45°. At θ = 45°, the largest u occurred at large heights as h p / H increased because parapets would lift up the roof flows. The largest amplification factor of wind energy decreased linearly as h p / H increased from 0 to 1/160, whereas no obvious variations for h p / H were observed from 1/160 to 1/80. The average hub height increased from 1.13 to 1.16 as h p / H increased from 0 to 1/80, indicating potential higher installation cost of wind turbines for larger h p / H. Analysis of parapet height is required to fully assess the wind energy potential and determine the layout of rooftop wind turbines. [ABSTRACT FROM AUTHOR]

In general, rotating objects (antennas, tops, flying birds with tails) always produce different rotational torques according to different dimensions and rotational speeds. In some cases, it can cause a lot of damage to equipment, so it is necessary to be aware of the amount of torque that rotating objects produce at different rotational speeds, as well as in the presence or absence of air flow. Due to the importance of this issue, in this study, numerical and experimental analysis of non-continuous flow around a cylindrical model with vertical plates under forced rotation is performed and its main purpose is to measure the torque of rotating objects in the presence of wind current and also to stabilize rotation. Rotational speeds are constant. First, an aerodynamic torque measuring device was built and then a 3-fin cylindrical model was tested in a wind tunnel, and numerical simulations of 3 and 2 fin models were performed in the same laboratory conditions by Ensys Fluent software. A good agreement was observed between the experimental and numerical results and the maximum error between them was less than 10%, which is acceptable. From the simulation results, it was observed that in every 180 degrees of rotation that the maximum cross section of the models is exposed to direct wind flow, the maximum torque produced by the 2-blade cylindrical model is 30% higher than the maximum torque produced by the 3-blade model. As the wind speed increases from 20 to 60 meters per second, the torque of the 3 -fin model increases from 0.4 to 1.2 Nm, which is equivalent to 200%. [ABSTRACT FROM AUTHOR]

Energy harvesting from piezoelectric materials is quite common and has been studied for the past few decades, but, recently, there have been a lot of new advancements in harnessing electrical energy via piezoelectric materials. In this regard, several studies were carried out in electrochemistry and fluid flow. Furthermore, consideration of productive and valuable resources is important to meet the needs of power generation. For this purpose, energy harvesting from fluids such as wind and water is significant and must be implemented on a large scale. So, developing self-powering devices can resolve the problem like that, and piezoelectric materials are gaining interest day by day because these materials help in energy generation. This review paper discusses different techniques for harnessing energy from fluid flows using piezoelectric materials. In addition, various vibration-based energy-harvesting mechanisms for improving the efficiency of piezoelectric energy harvesters have also been investigated and their opportunities and challenges identified. [ABSTRACT FROM AUTHOR]

The investigation of wind pressure distribution on a façade of an atypically shaped 162 m tall building is discussed in this paper. The horizontal cross-section was changed with the height of the structure (the square in the bottom part and the polygon in the top). The surface of the structure was smooth. A structural system was created using a combination of the tube structural system and exoskeleton structure. The building was stand-alone, located in urban terrain. In this case, the information in standards were not sufficient for its design. Therefore, other available tools had to be used for the determination of required input parameters (mean external pressure coefficients). At first, wind tunnel tests (WT) were performed on a reduced-scale model (1:300). Then, the obtained results were compared with data from a computational fluid dynamics (CFD) simulation. The accuracy of the simulation was evaluated by the method of three metrics. Short descriptions of the reduced-scale model, boundary layer wind tunnel, used measuring devices, and the methodology of tests are mentioned. The aim of this research was to identify the influence of the shape modification on the values of mean external pressure coefficients (in the comparison with the original shape, which was the cuboid). In the case of the cuboid, good agreement between the values determined by the CFD and the values from Eurocode was achieved. Larger discrepancies occurred on the roof. The modification of the total shape of the structure from the cuboid to atypical structure had the positive effect on the mean values of external pressure coefficients cpe. These values were smaller (at some levels significantly). Mainly, this effect was noticeable on the leeward side. For the wind directions 0° and 180°, the changes of the values were relatively large. For the other two wind directions (45° and 67.5°), the values on the windward sides were similar. The large advantage of this atypical structure is that the negative pressures on side walls and leeward side are smaller in the comparison with the cuboid. This is very useful for the fixing of façade components, where the values of negative pressures are larger than the positive pressures on the cladding in the larger heights. [ABSTRACT FROM AUTHOR]

In order to solve the problem that it is difficult to determine the range of the minimum wind flow of air directional drilling technology in soft-fragmentized coal seam, in this paper, loading of cuttings in air drilling is analyzed, and the critical incipient velocity of cuttings and the minimum wind flow under different grain sizes and different dip angles is calculated, and the distribution and variation of air flow rate in the borehole are analyzed by numerical method. The results show that the critical starting velocity of cuttings is maximum when the inclination of the borehole is about minus 30°, and the critical starting velocity of cuttings carrying rock is consistent with the minimum air flow rate under the conditions of different inclination angles and different grain sizes. In the radial direction, the air velocity is the largest at the center of the annulus section, and gradually decreases toward the wall of the hole on both sides and the wall of the drill pipe or the wall of the drill pipe and the inner wall of the drill pipe. In the axial direction, the air velocity increases gradually from the hole mouth to the bottom of the hole, and an obvious high-low velocity zone is formed at the bottom of the hole. When the air flows through the joint of the drill bit and the drill pipe, a sudden expansion effect is produced, which causes the air velocity to suddenly decrease, forming a obviously high-low velocity laminar flow zone, subsequently, the air velocity in the annular gap between the drill pipe and the hole wall tends to be stable.

• Experiments are conducted to study the heat feedback mechanism and mass burning rate of two unequal pool fires with wind flow. • Various parameters, including pool size, the relative positioning of the two pools, pool spacing, and cross-wind speed, are varied. • The evolutions of heat feedback, air entrainment, and blockage effects on mass burning rate are revealed. • A correlation for mass burning flux is proposed, grounded in stagnant layer theory. This paper aims to elucidate the heat feedback mechanism and burning characteristics of unequal n-heptane fires with wind flow. A total of 98 experimental cases were performed, involving a single pool and two unequal tandem pools (side length, D : 10 cm and 16 cm) with six pool spacings (S : 10–140 cm), across seven wind speeds (U : 0–5.0 m/s). The flame geometry, fuel mass, heat feedback components (radiation, conduction, and derived convection), and airflow were systematically recorded. The results indicate that the mass burning rate (m ˙) can be categorized into three phases: rapid growth, decay, and slow growth, with increasing U. Due to the blockage effect and constraint air entrainment, the critical wind speed at which m ˙ of the downstream pool attenuates is larger than that of the upstream pool. Concerning the blockage effect, it is observed that the airflow bypassed the upstream flame, reaching the downstream fire instead of passing through the upstream flame. The intensity of the blockage effect increases with the size of the upstream pool, while it decreases with wind speed (U) or pool spacing (S). With increasing S , the primary mechanisms governing fire interactions shift from constraint air entrainment to enhanced heat feedback, ultimately to blockage effect. The heat feedback fractions of the upstream pool are close to that of a single pool, indicating that the interaction effect on the upstream pool can be ignored at large spacings. The dominant heat feedback of the downstream pool changes from radiation to convection with increasing U. Finally, a model for the mass burning flux is established based on stagnant layer theory. [ABSTRACT FROM AUTHOR]

Airborne dust deposition on the solar photovoltaic panels can significantly decrease the photovoltaic efficiency performance. Dust deposition characteristics and influences on building-integrated photovoltaic panels were studied by shear stress transfer k-ω turbulence model with inlet profiles and discrete particle model. The influences of dust size, wind velocity, and building roof inclination on the dust deposition behaviors were studied carefully. The air flow fields, the dust particle trajectories, the deposition rate on solar photovoltaic panels and the photovoltaic efficiency decrease by dust deposition were obtained and analyzed in the study. The three-dimensional simulation has great difference on the wind flow structures compared with two-dimensional simulation. The size of the separation vortex in the three-dimensional simulation is significantly smaller than that in two-dimensional simulation. The secondary flow structures become more significant in the rear of the building. The dust deposition rate is firstly increased and then decreased with the increasing of dust diameter. The maximum deposition rate is 2.54% for 150 μm particles. The minimum deposition rate is just 0.03% for 500 μm particles. The maximum deposition rate is 1.39%, 2.54% or 3.74% for the roof inclination angle of 16.7°, 22.6°or 36.9°, respectively. When particle size is 150 μm, the dust motions are determined by the air flow fields, mass inertia and gravitational settling. The photovoltaic efficiency reduction is significantly higher with increasing of dust size. The present model can conveniently estimate the photovoltaic efficiency decrease by dust deposition in realistic engineering application.

To investigate the influence of dust produced by multi-dust sources at a fully mechanized mining face with a large mining height on the safety conditions in a coal mine, the No. 22305 fully mechanized mining face of the Bulianta coal mine was considered as the research object in this study, and the space–time evolution of dust was analyzed with computational fluid dynamics (CFD). The wind flow simulation results show that the distribution law of wind flow is mainly affected by the structure of the roadway, and the speed and direction of the wind flow change greatly while passing by corners and through large-scale equipment. The dust generation and pollution diffusion laws with respect to time and space were investigated based on simulations of dust production due to 5-s, 30-s, and 60-s coal cutting, continuous coal cutting, and hydraulic support shifting. The space–time evolution law under different dust-producing times shows the transportation and diffusion procedure of dust under the wind flow; the dust-generated via coal mining and shifting were superposed on the downwind side and a 36-m-long dust belt was formed, which filled the coal mining space; the dust concentration in the breathing zone 120 m downwind the front drum had a dust concentration higher than 1700 mg/m3, this was the crucial dust-proof area, and effective dust reduction methods should be addressed. [ABSTRACT FROM AUTHOR]

Due to ecological advantages wind technologies and theirs wide application is one perspective modern direction of power generation. In the paper presented the results of theoretical and practical investigations about the influence of the wind flow parameters in the Polissya region on the choice of the characteristics of the autonomous electric supply based on the wind turbine. In particular, the analytical dependencies are deduced for definition of: the power of the wind flow, the coefficient of the wind energy utilization, the produced electric power of the wind turbine and the yearly operation time of the installation. The practical investigations are shown in graphical dependencies of the coefficient of the wind energy utilization from the speed of the turbine rotor and dependencies of the wind turbine power capacity and the wind-to-rotor efficiency from the wind speed. Also, according to the mean wind speed distribution over the months nomogram (years 2011 to 2021) and according to monthly part of the wind suitable for wind energy, the choice of the of the low power wind turbine is substantiated. Using the method of statistical distribution, namely the Rayleigh distribution, normal distribution, by the mean value (wind speed) and the empirical distribution function the wind speed probability density. It is defined that use of the Rayleigh distribution makes possible to raise the calculation precision by 18.8 % and 36 % compared to normal distribution and to the mean wind speed value accordingly. As a 100 % the value calculated from empirical data was accepted. During the calculations there were errors because of unevenness of power consumption and the pulsing nature of power delivery. To avoid those errors, in future, it is recommended to use mathematical and computer modeling. The received calculation of the parameters of the system's elements of the autonomous power supply based on the wind turbine adapted to the characteristics of the Polissya wind flow, evidence the possibility of providing the reliable and uninterrupted power supply in this region. [ABSTRACT FROM AUTHOR]

The port of Bushehr, with its valuable and unique historical texture, completely matches with its unbearable climate conditions. Over hundreds of years, the port has provided an appropriate ground for human life as no air conditioner is needed there. Unfortunately, this valuable old texture has been destroyed inadvertently. New buildings in the port are just superficial copies of the old buildings’ external surfaces, with no attention to their goal, i.e., the provision of thermal comfort for inhabitants. The new buildings are dramatically increasing without considering the historical texture and climate. As a result, the inhabitants have to use air conditioners in most months continuously; hence, there would be an increase in energy consumption and a disruption in climate balance. This study has been conducted to compare the compatibility of such architecture with the climate and its success in providing climate comfort for the inhabitants. According to the information obtained from the study, the old houses built more than 100 years ago using traditional design had better performance in adaptability with climate. Accordingly, the exploitation of traditional instructions and patterns in a new format would largely reduce energy consumption in hot seasons and eliminate the need for heating in cold seasons. In this regard, a huge amount of energy is saved, resulting in less damage to the environment.

Together with the natural environment, the built, artificial environment represents a barrier to the wind fluxes. Especially in the densely built cities, the wind flow pattern and the wind speed are considerably altered by buildings, which can lead to zones of an accelerated wind and turbulent flow. Incorporating the wind into the early conceptual stage of architectural design, this reciprocal interaction of the built environment and the wind fluxes can be analyzed and controlled to create zones of calmer wind around buildings. Presently, building envelopes are designed to withstand extreme load cases, which, however, demands thicker and bulkier structures. The subject of this study is a proposal and investigation of a lightweight, adaptive building envelope, which is able of a local, passive morphing in the wind. This local shape change leads to creating a textured, dimpled building surface; the final shape depends on the wind direction and force. The wind-induced dimpled surface influences the wind flow around the building, as well as surface wind pressure acting on the building, and the drag force. The analysis of three fundamental building shapes using the CFD (Computational Fluid Dynamics) simulation is performed for the variants with and without the proposed adaptive envelope. Concluding from the wind simulations, the wind flow can be decelerated, the turbulence reduced, and calmer zones around buildings can be created, by certain conditions. Moreover, the envelope, morphing with the instant wind force, can contribute to the reduction of the surface wind suction on buildings. Strikingly, the dimpled geometry of the wind-adaptive envelope can decrease the wind drag force by up to 28.4 %, which is again dependent on the global form, as well as the initial wind speed.

In the need of more facilities and comfort, people are compelled to migrate from rural areas to developed cities. The growing population in urban areas, demand dense and facilitated building structure along with peripheral infrastructure. The current study uses OpenFOAM to analyse the impact of infrastructure development on wind profile and temperature of the surrounding area along with the cooling effect of vegetation cover. Air temperature and wind velocity are calculated at different points in the study region and are compared for various scenarios. The maximum change in the air temperature and wind velocity is found as 0.7 K and 0.4 m/s respectively due to an increase in building temperature during the day, while the minimum change is about 0.05 K and 0.1 m/s in densely vegetated areas. An assumption also has been taken to predict the vegetation cooling effects in surrounding buildings and is analysed with the temperature difference of 0.1 K to 0.5 K. The integrated analysis of wind and temperature around the infrastructure shows the magnitude of the impact constructed sites generates on urban microclimate and the results can be used for designing of a regulated area in terms of microclimate.

This work addresses the problem of modeling wind flow over complex terrain using three-dimensional cellular automata (3D-CA). We consider a 3D cellular discretization of the geographical field under study. To show the heterogeneity of space, in each cell, we have considered some attributes that affect the wind flow (landforms, land use and vegetation cover). The simulation results presented in this work have been realized using software developed in Java. The software offers many functionalities, in particular, data import and export, view scene in 3D and tools for processing the output data. For the areas considered, the input data were collected and processed using optical and radar remote sensing methods and tools. [ABSTRACT FROM AUTHOR]

The search for sustainable and sustainable actions, points its efforts in the use of renewable energies. Wind energy is one of these, which are used in different parts of the world; Europe has appropriated its use by strengthening the value chain. Colombia is embarking on its implementation, but it is in the initial phase. In Quindío, there are no references for the use of wind energy. This project proposes to design and build a vertical type wind turbine to generate electrical energy in Tecnoacademia in Armenia; implement a software for the physical modeling of air flow, turbulence, heat transfer, that allow the industrial applications of the prototype, extending its usability to the business sector of the region. [ABSTRACT FROM AUTHOR]

This article deals with the investigation of wind effects on a façade of a rectangular residential building with explicit modelling of the windows for specific wind conditions. The external wind pressure coefficients were treated on the façade and at the places of the window sills, linings, and lintel for the direction of the wind from 0° to 90° with increments of 22.5°. For a detailed analysis, the CFD simulation using Ansys Fluent was used. The method selected for the CFD simulation solution and its setting (quality of meshing, horizontal homogeneity of the boundary layer, etc.) were verified by known results of similar objects. The purpose of this analysis is to show how important it is to consider wind effects to determine the suitable placement of passive ventilation devices. Research shows the potential optimal position of ventilation units in terms of favourable pressure distribution. Zones with negative pressure and corners or façades in a wake are not suitable for applying passive ventilation units. The results can serve as a basis for designers to achieve optimal comfort in residential buildings.

Economic growth in ASEAN countries encourages significant urbanized growth. In line with the growth of urbanization, large swathes of residential buildings have been constructed in urban areas, especially, in the case of Indonesia, through the government's 1000 rusun (high-rise affordable housing) development program in Jakarta. In order to reduce energy consumption and create a sustainable rusun, a passive strategy is needed in the form of natural air conditioning through optimized natural ventilation in these buildings. In this study, testing was conducted on Rusun Rorotan in Jakarta, from two wind source directions (north and northwest) with five void decks configuration samples each, in order to determine wind flow and wind speed patterns in the Rusun area. For this purpose, the wind tunnel simulation method using the Butterfly plugin in Grasshopper was employed. These results should provide a reference for future residential property developers, especially in the scope of other countries in ASEAN, which have similar climatic conditions to that of Indonesia.

Introduction: Nowadays, cities are facing problems such as overheating caused by urban congestion, causing thermal islands and environmental problems, which make life difficult in some places. The wind flow in the urban environment is an important factor affecting the exchange of heat and moisture, particle transport, and urban ventilation. Studies show that physical factors such as enclosure change, the elevation of buildings, and different orientations of passageways in urban texture affect the speed and direction of the wind flow. The purpose of this study was to analyze climate data related to wind flow in two urban areas of Dezful and investigate the effect of enclosure of passages on the wind flow. Material and methods: In order to carry out the study, two areas of Siah-Pushan and Gozare-Shahi in the range of historical texture of Dezful, with similar and different physical factors, were selected for the analysis of physical conditions by comparing climate data. Data on the intensity of the wind and the ambient temperature of both areas in five periods of 9 -11 am, 11am-1 pm, 2-4 pm, 4-6 pm, and 6-8 pm, and in two seasons, winter and summer, were selected. Then, the enclosure of the collected points was calculated and using the linear regression analysis, the relationship between enclosure and wind speed was assessed. Results and discussion: The results showed that the velocity of the southwest-northeast wind flow was more than other orientations. Also, surveys showed that increasing the specific enclosure can increase the wind speed by a certain magnitude. In Gozare-Shahi, the results of the regression diagrams in the winter indicated that a direct relationship exists between the enclosure of the cross-sections and the velocity of the wind. With the minimum enclosure (0.35) increasing 1.5 to 3 times, the initial velocity of wind increased up to 31- 121 percent. The results of the linear regression diagrams in Siah-Pushan indicated that with 2 to 6 times increase in the enclosure, the wind speed increases up to 1.1 to 1.8 times. The results obtained from the linear regression diagrams in Gozare-Shahi passage showed that the enclosure of passways and the velocity of the wind flow are directly correlated. With the minimum enclosure (0.35) increasing 1.5 to 3 fold, the initial velocity of the wind increased 10 to 40 percent. In Siah-Pushan range, the enclosure of transitions was directly correlated with the wind. Also, the results showed that by increasing the enclosure up to 2 to 6 times, the velocity of the wind increased 1.03 to 1.20 times. Conclusion: Increasing the velocity of the wind led to better ventilation in the urban environment. On the other hand, increasing the enclosure increased the velocity. Uniform buildings, as well as regular enclosures with the least changes, will increase the velocity of the wind stream, as well as less turbulence. Thus, increasing enclosure, as well as regular buildings, can ultimately lead to better urban environments.

The investigation of wind pressure distribution on a façade of an atypically shaped 162 m tall building is discussed in this paper. The horizontal cross-section was changed with the height of the structure (the square in the bottom part and the polygon in the top). The surface of the structure was smooth. A structural system was created using a combination of the tube structural system and exoskeleton structure. The building was stand-alone, located in urban terrain. In this case, the information in standards were not sufficient for its design. Therefore, other available tools had to be used for the determination of required input parameters (mean external pressure coefficients). At first, wind tunnel tests (WT) were performed on a reduced-scale model (1:300). Then, the obtained results were compared with data from a computational fluid dynamics (CFD) simulation. The accuracy of the simulation was evaluated by the method of three metrics. Short descriptions of the reduced-scale model, boundary layer wind tunnel, used measuring devices, and the methodology of tests are mentioned. The aim of this research was to identify the influence of the shape modification on the values of mean external pressure coefficients (in the comparison with the original shape, which was the cuboid). In the case of the cuboid, good agreement between the values determined by the CFD and the values from Eurocode was achieved. Larger discrepancies occurred on the roof. The modification of the total shape of the structure from the cuboid to atypical structure had the positive effect on the mean values of external pressure coefficients cpe. These values were smaller (at some levels significantly). Mainly, this effect was noticeable on the leeward side. For the wind directions 0° and 180°, the changes of the values were relatively large. For the other two wind directions (45° and 67.5°), the values on the windward sides were similar. The large advantage of this atypical structure is that the negative pressures on side walls and leeward side are smaller in the comparison with the cuboid. This is very useful for the fixing of façade components, where the values of negative pressures are larger than the positive pressures on the cladding in the larger heights.