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The urban street is an important part of the urban form and serves as the primary medium for public activities within cities. The morphological characteristics of urban street space not only influence people's spatial experience but also have an impact on the quality of the physical environment, such as the wind environment. Numerous scholars have studied the wind environment of streets with different morphological characteristics using abstract and simplified street models, uncovering certain relationships between specific morphological features and airflow patterns. However, due to the significant disparity between simplified models and reality, researchers have attempted to develop models applicable to the complex characteristics of urban street space, with the aim of exploring the relationship between street spatial features and airflow characteristics. This study explores a method to quantify the complex spatial characteristics of urban streets, using a series of parameters to describe the streets, such as average width, proportion of secondary interfaces, and proportion of opening length. Streets with different spatial characteristics in the centre of Nanjing are selected and quantified. A comparison is conducted between the parameters representing street spatial morphology and the simulation results of the wind environment in the area, aiming to assess the effectiveness of these parameter values. The results demonstrate that complex urban spaces can still be effectively represented through parameterization and confirm the validity of our quantitative representation of complex street spatial characteristics. The results could serve as a reference for urban design and urban construction. [ABSTRACT FROM AUTHOR]

Abstract Computational fluid dynamics (CFD) was used to reproduce wind fields around a twin-box girder. Wind tunnel tests and field measurements were conducted to verify the accuracy of the CFD results. Variations in wind speed at different heights and crosswind reduction effects with different barriers were also examined using CFD simulation; the barriers had significant reduction effects. The reduction effectiveness was closely related to the barrier height and position; porosity was also a crucial factor. The wind speed profiles of a twin-box girder and a single box girder were analysed to determine why the wind speeds above the downstream deck were lower than above the windward deck of the twin-box girder. The results show that the incoming flow leaked downward through the slotted parts of the bridge and formed regulation vortices. Wind speeds were lower above the downstream deck than above the upstream deck as a result of leakage effects. The gap width also influenced the wind environment around the bridge deck.

Computational fluid dynamics (CFD) was used to reproduce wind fields around a twin-box girder. Wind tunnel tests and field measurements were conducted to verify the accuracy of the CFD results. Variations in wind speed at different heights and crosswind reduction effects with different barriers were also examined using CFD simulation; the barriers had significant reduction effects. The reduction effectiveness was closely related to the barrier height and position; porosity was also a crucial factor. The wind speed profiles of a twin-box girder and a single box girder were analysed to determine why the wind speeds above the downstream deck were lower than above the windward deck of the twin-box girder. The results show that the incoming flow leaked downward through the slotted parts of the bridge and formed regulation vortices. Wind speeds were lower above the downstream deck than above the upstream deck as a result of leakage effects. The gap width also influenced the wind environment around the bridge deck. [ABSTRACT FROM AUTHOR]

The risk of damage of glass curtain walls in residential areas caused by impact of wind-borne debris has been given increasing importance. In this paper, by incorporating the numerical analysis of three-dimensional (3D) flight trajectories of wind-borne debris and computational fluid dynamics (CFD) simulation of the local wind environment in the context of buildings group, a novel impact damage prediction model for the glass curtain wall of urban buildings is proposed. To this end, the 3D flight trajectories and characteristics of plate-type debris are first studied by solving the 3D equation of motion of debris, of which the aerodynamic coefficients of plate-type debris is obtained by CFD numerical simulation. The flight characteristics of debris with different initial parameters are analyzed, showing that the properties of debris and initial conditions have significant effect on the flight trajectories and impact position of plate-type debris. Further, an impact damage prediction model for the glass curtain wall of an urban building is proposed. In the proposed model, the flight trajectory analysis of the wind-borne debris is embedded in the context of the local wind environment in a residential area obtained by CFD simulation. The damage caused by the impact of debris on the glass curtain wall of the buildings is then analyzed and illustrated by an example. The proposed model is of great significance for the wind damage analysis of urban building glass curtain walls considering local wind environment and real trajectories of debris. [ABSTRACT FROM AUTHOR]

Affected by many factors, the local wind environment on the bridge deck is complex and changeable, and it seriously threatens traffic safety. To accurately evaluate the wind field on the bridge deck, this paper develops a system to monitor the actual local wind environment and applies it to field measurement of the wind parameters at different positions of a complex truss girder bridge. The results show that the wind parameters on the bridge deck, including wind speed, gust factor, and turbulence intensity, are different from the bridge site due to the influence of the ancillary facilities. Also, the wind profile of the local wind field on the bridge deck is more in line with the polynomial distribution, which makes the equivalent height of the wind load much higher than the vehicle gravity. It should be noted that the measured power spectrum of the bridge deck is quite different from the wind spectrum applicable to the bridge site area, so it is not appropriate to use the wind spectrum of the bridge site area to carry out the analysis of the windmill bridge, and a more suitable wind spectrum for bridge deck wind field is proposed. [ABSTRACT FROM AUTHOR]

The urban street is an important part of the urban form and serves as the primary medium for public activities within cities. The morphological characteristics of urban street space not only influence people’s spatial experience but also have an impact on the quality of the physical environment, such as the wind environment. Numerous scholars have studied the wind environment of streets with different morphological characteristics using abstract and simplified street models, uncovering certain relationships between specific morphological features and airflow patterns. However, due to the significant disparity between simplified models and reality, researchers have attempted to develop models applicable to the complex characteristics of urban street space, with the aim of exploring the relationship between street spatial features and airflow characteristics. This study explores a method to quantify the complex spatial characteristics of urban streets, using a series of parameters to describe the streets, such as average width, proportion of secondary interfaces, and proportion of opening length. Streets with different spatial characteristics in the centre of Nanjing are selected and quantified. A comparison is conducted between the parameters representing street spatial morphology and the simulation results of the wind environment in the area, aiming to assess the effectiveness of these parameter values. The results demonstrate that complex urban spaces can still be effectively represented through parameterization and confirm the validity of our quantitative representation of complex street spatial characteristics. The results could serve as a reference for urban design and urban construction.

Abstract The local wind environment and daylight conditions of buildings directly affect the safety and comfort (e.g. thermal environment and lighting environment) of the residents and staff, and influence the energy consumption and energy efficiency of building's operation. However, in the view of a planning designer, it is likely to pay more attention to the building's functional arrangement, appearance and space utilization, but the problems of area ventilation and daylight condition may be neglected. This paper takes a layout design of a commercial building group in Haidong, Qinghai Province as an example to demonstrate, for an urban planner, how to use the CFD and building lighting simulation technology to carry out the preliminary evaluation on an initial design scheme. Simulation results indicated under local meteorological conditions, the initial design scheme fully considered the cold air infiltration in winter and natural ventilation in summer, as well as safety issues in the human walking area, which formed a good local wind environment. However, the problem of poor daylight condition in some areas requires adjustments and modifications based on actual circumstance. From the examples presented in this paper, the numerical simulation techniques play an important role at the initial stages of planning and design to detect the design defects timely and provides a basis for subsequent adjustments later. Meanwhile, this paper also provides a reference for interdisciplinary cooperation between urban planners and HVAC engineers. [ABSTRACT FROM AUTHOR]

In this present study, the wind environment was evaluated for local void domain at pedestrian level in the aspect of ventilation performance and thermal comfort. Exceedance probability analysis was applied as the main approach in order to estimate the uncertainties associated with the influence of climate on wind environment. Two criteria were proposed based on local air change rate and local kinetic energy respectively, which are domain-based indices allowing comprehensive estimation of local wind environment. Calculating output of these criteria in the form of cumulative distribution function forms a ground for reliability analysis of inadequate ventilation or thermal discomfort. A simple street canyon situated in Tokyo, defined as void model, was applied as an illustration of the new criteria in evaluating the local wind environment at ground level. The influences of two configuration factors: orientation and aspect ratio of the void model were investigated by CFD simulation. The results demonstrated that both factors show great influences on local ventilation performance, which also indicated the practicability and effectiveness of the proposed criteria to help achieving good wind environmental design. [Copyright &y& Elsevier]