Wind Environment Assessment Research Articles

Multi-Scale Urban Natural Ventilation Climate Guidance: A Case Study in the Shijiazhuang Metropolitan Area

The rapid development of urbanization has caused obstructed urban natural ventilation and the contribution rate of urbanization is relatively high. Therefore, there is an urgent need for urban development planning that should respect natural ventilation and local climate to reduce negative impacts. By optimizing the urban construction layout to reduce obstruction and leave a passageway for wind to blow in, the natural ventilation environment could be improved. This paper presents a promising approach for natural ventilation planning at both the city and community scales. Based on the assessment of wind environment, heat island intensity, and ventilation potential, the results revealed that winds blowing from the western and northern mountainous area of Shijiazhuang play a natural ventilation inlet role which can provide clean air. The SSHI and SHI were mainly distributed within the Second Ring Road, which has a large proportion of the low ventilation potential level. Thus, six first-class ventilation corridors and thirteen secondary corridors were recommended, which were set to be adapted to the dominant wind direction. Subsequently, an urban climate analysis map (UCAnMap) was developed considering climate sensitivity, and planning recommendations were provided for different climate zones. The relationship between architectural spatial structure and ventilation efficiency was analyzed; the results revealed that increasing the height of the buildings will decrease the proportion of comfortable wind zones, and the overall ventilation efficiency will weaken, so the average building height of a typical block should be controlled within 45 m, which matches ventilation performance requirements. The ventilation efficiency of the block has a certain negative correlation with the building density, and as the building density decreased by more than 10%, the proportion of the comfortable wind zones could increase by 4–5%.

Computational Fluid Dynamics-Aided Simulation of Twisted Wind Flows in Boundary Layer Wind Tunnel

The twisted wind flow (TWF), referring to the phenomenon of wind direction varying with height, is a common feature of atmospheric boundary layer (ABL) winds, noticeably affecting the wind-resistant structural design and the wind environment assessment. The TWF can be effectively simulated by a guide vane system in wind tunnel tests, but the proper design and configuration of the guide vanes pose a major challenge as practical experience in using such devices is still limited in the literature. To address this issue, this study aims to propose an approach to determining the optimal wind tunnel setup for TWF simulations using a numerical wind tunnel, which is a replica of its physical counterpart, using computational fluid dynamics (CFD) techniques. By analyzing the mechanisms behind guide vanes for generating TWF based on CFD results, it was found that the design must take into account three key parameters, namely, (1) the distance from the vane system to the side wall, (2) the distance from the vane system to the model test region, and (3) the separation between the vanes. Following the optimal setup obtained from the numerical wind tunnel, TWF profiles matching both the power-law and Ekman spiral models, which, respectively, reflect the ABL and wind twist characteristics, were successfully generated in the actual wind tunnel. The findings of this study provide useful information for wind tunnel tests as well as for wind-resistant structural designs and wind environment assessment.

Urban wind field prediction based on sparse sensors and physics‐informed graph‐assisted auto‐encoder

AbstractThe urban flow wind field is a critical element for downstream research, such as mitigation of urban wind disasters, assessment of urban wind environment, and urban drone route planning. However, it is impractical to arrange a large number of sensors to monitor an urban wind flow field. Hence, acquiring the entire urban wind flow field via sparse sensors would be highly valuable. To date, no scheme including deep learning (DL) model has been specifically designed for this purpose. This study presents an innovative approach to reconstruct complex high‐resolution urban wind fields based on sparse sensors, using a physics‐informed graph neural network (GNN)‐assisted auto‐encoder. The proposed method leverages the relationship between sensors and their surrounding environment enabled by deep mining capabilities of GNNs. As a result, the utilization and emphasis on sparse sensors data are significantly enhanced. The continuity equation of fluid flow is incorporated into the loss function of the convolution neural network to improve the stability and performance of the model. The findings suggest that, in contrast to prevalent generative DL models, the proposed model yields an approximate 50% reduction in root mean square error for reconstructing high‐resolution urban wind fields for multiple wind attack angles.

A workflow for rapid assessment of complex courtyard wind environment based on parallel lattice Boltzmann method

A fast courtyard wind simulation platform based on the parallel courtyard Lattice Boltzmann Method (CLBM) is proposed to achieve comprehensive optimization of courtyard design structure and wind environment performance. The simulation workflow of CLBM is designed and implemented, and its accuracy is validated using two benchmark cases and Qinghui Garden in central Guangdong. The results show that CLBM achieves simulation accuracy on par with other simulations, with R2 values greater than 0.8 and Root Mean Squared Error (RMSE) values less than 0.3 m/s for the building array case and RMSE values less than 0.2 m/s for the row of trees case. In the testbed courtyard, the Normalized Root Mean Squared Error (NRMSE) values range from 0.18 to 0.30, close to Ansys Fluent's NRMSE values of 0.07–0.33, and comparable to most peer studies with NRMSE values below 0.5. CLBM is also faster than traditional Computational Fluid Dynamics (CFD) models, with a workflow that is 19 times faster than Ansys Fluent and can produce wind environment simulation feedback in about 10 min. This model's speed and accuracy advantages make it well-suited for quickly simulating courtyard wind environments, even in the presence of complex combinations and rich vegetation. Architects can use this technique to regularly experiment with courtyard design elements and achieve evidence-based design of courtyard ventilation to fully realize the aesthetic appeal and maximize ventilation efficiency.

CFD를 이용한 보행자 풍환경 평가 기법의 적합성 분석

Recently, due to increased urbanization with high-rise buildings, there are growing concerns about the wind environment that threatens the safety of pedestrians as well as facility damage caused by the building wind. In order to reduce building wind damage, it is important to improve the wind environment of the urban environment by applying preemptive measures through the evaluation of the wind environment around buildings. Besides conventional wind tunnel tests, CFD has recently been accepted an alternative or a supplementary tool for the assessment of wind environment on the pedestrian level. As one of the practice in the field, MOLIT recently proposed Wind Environment Evaluation Guidelines Using CFD Analysis Techniques. This paper presents a computational study to confirm the feasibility of the pedestrian wind environment evaluation method using CFD based on the guideline. To verify the results of CFD, models and wind tunnel experiment data by provided by Architectual Institute of Japan were employed. Various grid configurations and numerical methods as well as varied wind directions were applied. The comparison between experimental data and the present results show that the grid refinement improves the accuracy and the pedestrian wind can be assessed by using CFD in spite of some deficit and room for improvements. More importantly, the gusts caused by the upwind and downwind in upwind region of the building, and vortex around the building were well simulated.

Wind environment assessment and planning of urban natural ventilation corridors using GIS: Shenzhen as a case study

The development of high-density cities has aggravated the harshness of the urban microclimate in face of global warming. However, an adequate urban ventilation system can introduce clean and cool air into high-temperature areas of a city, which can alleviate the urban heat island (UHI) effect and increase residents' thermal comfort. In this study, we devise an integrated air ventilation assessment (IAVA) method to assess the urban wind environment using multi-source data, with Shenzhen as an example. The IAVA map illustrates that developed areas in the south and west of Shenzhen form a “wind wall” that reduces wind speeds and prevents wind flow into inland areas. In light of the results of the IAVA, potential ventilation corridors across Shenzhen are then created using the least cost path method. Subsequently, the optimized ventilation corridors are generated via super-imposition over a satellite image and the identification of functioning and compensating areas. Notably, the IAVA introduces the effects of terrain, vegetation, and open space, thus providing a more pragmatic evaluation of the wind environment than frontal area density results. Furthermore, it provides planning guidance for local governments that considers the quality of the urban wind environment in the low-cost and efficient construction of ecological and livable cities.

Pedestrian-Level Wind Environment Assessment of Shenyang’s Residential Areas through Numerical Simulations

In recent decades, increasing urbanization has increased construction land shortages, which has made people pay more attention to the utilization of vertical space. The emergence of more and more high-rise buildings has affected the wind environment at the pedestrian level, especially in residential areas. In this research, the typical patterns of the layouts of residential buildings in Shenyang were investigated and summarized, and the wind environment of the residential areas of different architecture layouts was simulated according to the climatic conditions in Shenyang. After analyzing the simulation results, a typical layout mode for the residential areas in Shenyang was developed to facilitate the establishment of a favorable wind environment. In comparison with different building layouts, a staggered layout of slab buildings, half-enclosed layout of point buildings with openings on the south side, slab-point combined buildings with slab buildings on the north side, and point buildings on the south side were found to be the most suitable layouts for Shenyang’s climate. Thus, this study can provide guidance to designers and urban planners in addition to practical suggestions for residential planning.

Impact of volume distribution on pedestrian wind environment in high-rise urban districts: a CFD study

Pedestrian wind environment assessment is becoming an essential part of the urban design process especially in dense urban areas due to its ability to address the wind comfort/safety/health concerns in an early phase. In this paper, high-fidelity computational fluid dynamics (CFD) simulations, validated with experimental data, are performed on eight different designs in a generic urban layout to study the impact of volume distribution on pedestrian wind environment in high-rise urban districts. The results show that the blockage effects of the high-rise buildings decelerates the wind in the streets parallel to the flow while accelerating the flow in the streets perpendicular to the flow. This effect is evident up to a two block distance upstream of the high-rises. Furthermore, it is shown that consequent rows of high-rises in the downstream of the first row facing the wind flow have little effect on the upstream pedestrian wind; however, they have a significant role in the extent of affected areas downstream. The findings of this study provide further understanding about the impact of different volume distributions on pedestrian wind environment in high-rise urban districts and clarify their effect on wind safety and comfort.

Simulation Methodology Based on Wind and Thermal Performance for Early Building Optimization Design in Taiwan

In a subtropical climate like that of Taiwan, the high temperature and humid environmental conditions often result in discomfort and health effects for building occupants. With regard to building geometry, the wind environment and thermal comfort assessment, which can enhance energy efficiency and the comfort and health of occupants, both ought to be considered as soon as possible in the design process. In view of the limited comprehensive design evaluation methods and design workflows regarding wind and thermal performance currently available, this research aims to develop an early decision support workflow that includes suggested performance evaluation methods and design optimization processes. The results of our case study show that the building had clear performance results using the proposed evaluation methods, making it easier for architects to understand and compare alternatives. Appropriate analysis and visualization of the results also effectively assisted architects in determining design solutions and making relevant decisions. The methods and results in this article can facilitate performance-based buildings for healthy and energy-efficient built environments.

Classification and pedestrian-level wind environment assessment among Tianjin's residential area based on numerical simulation

In this study, Tianjin's 36 practical residential areas were classified into four main categories and nine subcategories of layout modes based on actual planning methods. The wind conditions of each layout mode were evaluated with ENVI-met software and compared using three wind environment factors: wind speed, calm wind area ratio and wind speed dispersion. Further, correlations between spatial morphological factors and wind environment factors were established. Results indicate that the classification method of layout modes used in this study can fully reflect spatial differences between real residential areas. From comparison of the three wind environment factors, the mid-rise enclosed mode was found to exhibit the worst wind environment due to its low wind speed while the mid-rise parallel and mid high-rise modes are recommended as the most suitable for Tianjin's climate. The wind environment of high-rise layout modes are not as favourable as the wind environments of the mid-rise and mid high-rise modes. Frontal area density and average building height are shown to be key spatial morphological factors which affect the pedestrian-level wind environment. They can be used in residential planning practices to improve the wind condition. This research presents an opportunity to assist urban planners and researchers in developing a comprehensive understanding of pedestrian-level wind conditions in different residential layout modes.

Development of probabilistic assessment framework for pedestrian wind environment using Bayesian technique

This study extends the assessment framework proposed by Murakami et al. (1986) for the pedestrian wind environment to a fully probabilistic method by implementing Bayesian modeling. The method quantifies the uncertainties in constructed models based on the measured wind data and the results of the assessment. To model the probabilities of the daily maximum mean wind speed and wind direction, we employed the Weibull distribution and categorical distribution, respectively. The parameters defining the probability distributions were probabilistically modeled using Bayesian techniques. Using the wind data measured at the Meteorological Observatory of Tokyo, we demonstrated the effectiveness of the proposed method. The results showed that the wind direction probability and each parameter of the Weibull distribution could be estimated in the form of a posterior probability density function. Using the constructed models, we predicted the exceedance probability of the daily maximum instantaneous wind speed and evaluated the wind environment index (rank) in a city model. We provided a discrete rank scale in the form of a probability distribution, which enables us to quantify the evaluation uncertainties. Additionally, we clarified the effect of varying the amount of data used for the model construction. The uncertainty of the exceedance probability decreased with the amount of data. When only 1 year of data was used, some evaluation points possibly changed over three ranks. Even when 5-year observation data was used, the evaluated rank of some points varied within the range of uncertainty, thereby highlighting the importance of uncertainty quantification in the wind environment assessment.

Exceedance Probability Assessment of Pedestrian Wind Environment Based on Multiscale Coupling Numerical Simulation

AbstractThis paper presents exceedance probability assessment, which is a statistical evaluation method for pedestrian wind environment based on numerical simulations with multiscale coupling techn...

Wind tunnel Assessment of Wind Environment and Dust Suppression Effect of Windbreak in Port Bulk Storage Yards

Windbreaks projects are constructed in order to reduce the dusting in port bulk storage yards. The assessment of wind environment and dust suppression effects are important in the planning or preliminary design of such projects. This paper takes a large port bulk storage yard with 853m x 966m area as an example, velocity measurement wind tunnel tests were carried out. The wind velocity reduction ratio and dust suppression rate were used to access the wind environment and the dust suppression effect. The influence of windbreak height was investigated. The comprehensive wind speed reduction rate and dust suppression rate vary with windbreak height nearly linearly. And combined with spraying system, the dust suppression rate can reach beyond 95%, which provides reference and assessment method for relative engineering applications.

Improvement Strategies Study for Outdoor Wind Environment in a University in Beijing Based on CFD Simulation

The outdoor wind environment is one of the most important factors influencing the biological environment and human comfort. The campus of China University of Mining & Technology (Beijing) (CUMTB) is the case study for this research. PHOENICS simulation software was used to carry out a numerical simulation study of the outdoor wind environment. The pedestrian‐level wind (PLW) environments for both winter and summer were investigated. Based on the numerical simulation results, the overall evaluation and subregional analysis of the campus’ current outdoor wind environment were carried out. Then, according to the results and problems of wind environment assessment, improvement measures and strategies of outdoor wind environment in universities are proposed from the aspects of campus planning, single building form, and greening configuration. The main goal is to further improve the outdoor space and environment of universities in Beijing and provide general guidelines to improve the quality of the universities’ wind environment effectively. The strategies can provide a reference for the same type of campus on wind environment renovation and improvement. This study can also provide data support and reference significance for outdoor thermal environment/pedestrian environment research.

Criterion for wind environment assessment with consideration to the effect of turbulence

Criterion for wind environment assessment with consideration to the effect of turbulence

Practical Applications of the Large-Eddy Simulation Technique for Wind Environment Assessment around New National Stadium, Japan (Tokyo Olympic Stadium)

In this study, we developed a new computational fluid dynamics (CFD) model called Airflow Analyst that deepens the affinity between CFD and geographic information system (GIS). First, a precise simulation of the surface-mounted cube was conducted. Validation testing based on the obtained data confirmed the predictive accuracy of Airflow Analyst. Second, New National Stadium Japan (Tokyo Olympic Stadium) was accurately reproduced in a computer, capturing the latest detailed urban area data for the base. For the target of the constructed 3D models, simulations with a large number of grid points/cells (CFD) were conducted. These simulations reproduced the complex turbulent flow fields both inside and outside the stadium. The experiment successfully reproduced the CFD simulation using a large number of grid points/cells, where the conditions of the wind flow ventilation from the sky were similar to those of the intended stadium design.

風環境評価におけるベイジアンモデリングの実装 （第１報）日最大平均風速と風向の確率論的モデリング

風環境評価におけるベイジアンモデリングの実装 （第１報）日最大平均風速と風向の確率論的モデリング

Study on wind environment assessment criterion considering the influence of turbulence

Study on wind environment assessment criterion considering the influence of turbulence

Discussion on Difference between 3 Cup and Ultrasonic Anemometers of the Obtained Statistical Values to be Used for Wind Environment Assessment

Discussion on Difference between 3 Cup and Ultrasonic Anemometers of the Obtained Statistical Values to be Used for Wind Environment Assessment

Integrating CFD and GIS into the Development of Urban Ventilation Corridors: A Case Study in Changchun City, China

Given the situation of urban expansion and environmental deterioration, the government and researchers are paying considerable attention to ventilation corridors. The construction of urban ventilation corridors requires quantitative data support. Computational fluid dynamics (CFD) has advantages in the fine assessment of wind environment, and a geographic information system (GIS) has excellent performance in spatial analysis. With Changchun City used as an example, this study proposes the establishment of ventilation corridors on an urban scale to mitigate the urban-heat-island effect, and to accelerate the diffusion of air pollution. CFD simulations provided detailed spatiotemporal characteristics of wind speed and wind direction at various heights. These simulations were useful for identifying potential ventilation corridors. In general, the wind-speed and wind-direction characteristics at a height of 30 m clearly indicated potential ventilation corridors. Potential paths existed in the leading wind and south–north directions. The areas that required improvement were favorably situated in the path of potential ventilation corridors. The main roads, green spaces, and water had good connectivity. A total of five ventilation corridors were constructed, and they will directly affect the poor urban thermal environment, and enhance the mobility of air.