Wind Comfort Research Articles

Numerical Investigation of the Wind and Thermal Conditions in Sky Gardens in High-Rise Buildings

High-rise buildings are known to be highly energy intensive, adding stress on already stressed resources. Alternatively, designers are looking at passive strategies and investing in architectural elements, such as sky gardens, which could improve the performance of buildings. Sky gardens are green areas located in a building which are exposed to the outdoors. They could provide multifaceted improvements in buildings by introducing environmental benefits to occupants and altering microclimate. This study aims to determine the wind comfort and thermal condition in sky gardens in high-rise buildings using numerical modelling. Different geometrical configurations of sky gardens were simulated and analysed. Based on the initial results, the study reveals that sky gardens can generate high wind velocities of the order ~10 m/s when located on a high-rise building. The addition of features such as trees and other architectural elements, which can act as a buffer, can help attenuate the high wind speeds and creating habitable spaces. The reduction varies 50%–80%, depending on the location and spatial domain of the sky garden. Furthermore, the study also investigated the reduction in air temperature due to the addition of trees, which can further reduce temperature in hot weather.

Numerical analysis of the wind and thermal comfort in courtyards “skycourts” in high rise buildings

Over the years, skycourts have been built to solve problems of green space shortages while providing benefits towards social and environmental benefits to the urban habitat. It is an architectural feature that can provide an alternative to semi outdoors areas. Through the analysis of previous related works, it was observed that existing skycourts are not popular due to wind and thermal comfort problems. This has led to the investigation into the aero-thermal comfort in different skycourt designs within a high-rise building model using Computational Fluid Dynamics (CFD). Validation of the base model with experimental data showed good agreement. Through the simulation of several skycourt designs to obtain wind patterns across various skycourt levels, a general relationship between wind velocity of the approach flow and skycourt levels was made that lead to the determination of a wind velocity factor that allows comparison of wind comfort within any skycourt design. Using established wind comfort criteria, comfort within various skycourt regions were analysed. The results showed that skycourt designs have minimal effect on the temperature distribution particularly when vegetation is not considered. The study also investigated how skycourts would perform under more realistic conditions by adding heat sources representing internal gains within the interior spaces of skycourts. Future studies can focus on the investigation of skycourts with adjacent buildings and the effects of vegetation on aero-thermal performance. This would allow determination of skycourt performance under more realistic conditions.

Using simulation methods to investigate the impact of urban form on human comfort. Case study: Coast of Baltim, North Coast, Egypt

Coastal regions have specific climatic conditions, that require deliberate thinking before considering urban interventions. So, understanding these conditions is the starting point to lay out a responsive design that realizes the symbiotic relationship between nature and urban development in such a sensitive context. This paper analyses different parameters of the urban form, that control the outdoor human thermal, and wind comfort in the Egyptian coastal zone. It presents an experimental investigation of the microclimatic conditions, in selected districts, on the coast of Baltim (resort city in Egypt). It uses ENVI-met 4.0 Software to assess three environmental variables, namely: Air Temperature, Relative Humidity, Wind Speed, and one thermal index (PMV). It compares the results of simulating three different orientations of urban blocks in three different districts. The measurements were taken during both the summer and winter of 2018. In addition, the research focuses on correlating simulation results, at the selected sites, to the key parameters of the examined blocks, which are: Aspect Ratio (H/W), Street Orientation, and Building Volume. Finally, the results give an indication of the way in which design configurations of urban blocks could be controlled to enhance the microclimatic conditions in such coastal areas.

A parametric study of angular road patterns on pedestrian ventilation in high-density urban areas

Road patterns are highly related to urban ventilation, which plays an important role for improving thermal comfort at the tropics. However, the effects of road intersection angles on the pedestrian-level wind environment remain uncertain. This study investigates the effects of angular road patterns in high-density urban areas using experimental and numerical methods. The studied road patterns are developed from four types of four-way road intersections with various road intersection angles from 90° to 45°. A reduced-scale angular road pattern was first tested in a wind tunnel experiment for validation purposes. The experiment indicates that the Reynolds-averaged Navier-Stokes (RANS) method (κ-ε model) is appropriate to solve the flow in the angular road network. The conducted numerical parametric study suggests the flow field is affected by both the prevailing wind direction and the relative orientation of adjacent road segments (i.e. stream-wise versus lateral; and upstream versus downstream). Based on the results, recommendations are provided for orienting the segments in regular and irregular road networks. In general, upstream road segments should be closely oriented to the wind direction to maximize the overall incoming flow, while moderate inflow angles should be designed for downstream road segments to balance the downstream and lateral flow penetration. These design recommendations of road networks provide the possibility to improve the pedestrian-level wind comfort by optimizing the flow distribution without sacrificing the limited land resources in tropical compact districts.

Wind tunnel study on the pedestrian-level wind comfort in residential areas of Harbin

Pedestrian-level wind conditions in residential areas are closely related to the quality of urban residents' daily life. In this paper, seven representative building layouts of urban residential areas were summarized from actual residential areas of Harbin, and wind tunnel experiments were carried out to study the pedestrian-level wind comfort in these residential areas. The assessments of pedestrian wind comfort are performed by combining the wind tunnel results and long-term local wind statistics. The results show that the hybrid-type and the enclosed-type layouts can provide better pedestrian wind comfort than parallel-type layouts, and the building heights of residential areas need to be controlled in cities of severe cold regions.

Human Comfort Instrument Design Based on Embedded

The traditional human comfort meter has the following defects: the interface is not uniform; the operation is cumbersome and complicated; the interface is unfriendly, and the stability and adaptability are poor. This paper presents a design scheme for human comfort instrument based on embedded system, using S3C2440 embedded development board and the sensors to collect the real-time temperature, relative humidity and wind speed data and to process the collecting data; then obtaining the human body comfort value according to the basic algorithm of human body comfort instrument; giving the human comfort conclusion according to the diastolic index range of human comfort, and showing the temperature and humidity, wind speed, comfort value and conclusion through writing the Qt graphical user interface program. At the same time, the human comfort instrument has the data storage function. The human comfort instrument is high in integration, strong in real time, high in sensitivity, stable and reliable, and it meets the development goals of the intelligent meteorological service, and meets the demand of the meteorological service that is closer to life, and it has broad development prospect.

Improving schoolyard wind environments: Case studies in two schools in Nanjing

Wind environment as an essential aspect of urban micro-climate is usually studied as an important factor affecting human wind comfort and thermal comfort in public open space. Less studied is how wind environments influence schoolyard serving for children and teenagers who are more sensitive to air temperature and air pollution. This paper presents a study using XFlow for wind speed evaluation based on CFD (Computational Fluid Dynamics) simulation, and Ecotect Analysis for thermal comfort evaluation. Choosing Nanjing Mochou Lake Primary School and Nanjing NO.13 Middle School Suojin Campus as case studies, it offers an evaluation of wind environments in these two schoolyards and surrounding open spaces. Simulation shows that improvements should be made to build better wind environments around both schools. Scenarios are developed subsequently by adjusting buildings in study areas at the scale of blocks and school buildings, proving the efficiency of improvements for a more comfortable wind environments. This study focuses on schoolyard wind environments from the standpoint of children and teenagers, suggesting that research on urban micro-climate can be expanded in multiple directions so that as many social groups in different ages as possible benefits, i.e. have healthier urban life.

Atmospheric Boundary Layer Wind Tunnel of Slovak University of Technology in Bratislava

Aerodynamics is a relatively young scientific discipline, which started developing in the 50´s of last century. There are known several methods for calculating and measuring of the aerodynamic variables – in-situ measurements, wind tunnel measurements, CFD simulations and calculations according to national standards. Each method has its advantages and disadvantages. Nowadays a large focus is on experimental verifying the findings achieved with calculations help and CFD simulations. One of the verification possibilities are measurements in wind tunnels. The submitted paper deals with construction and using of the wind tunnel by the Slovak University of Technology in Bratislava. This device was put into operation after experimental verification in 2012, so this wind tunnel is one of the newest of its kind in Europe. The concept of the construction of individual structural elements and the wind tunnel parts has been designed in collaboration with the Aeronautical Research and Test Institute (Czech Republic) and was based on previous made analysis of aerodynamic tunnels. Its structure was designed and realized by Konštrukta Industry (Slovak Republic). We could it characterized as atmospheric boundary layer wind tunnel with open test section. It is unique with two test sections – front and back measuring space, where the front measuring space is used for uniform flow and the back measuring space is used for turbulent flow. That is why it is not only usable in the civil engineering sector (buildings, bridges, chimneys etc.), but also in city urbanism (pedestrian wind comfort and wind safety, dispersion of air pollutants), aircraft and automotive industries.

Developing Urban Environment by Focusing on Human Thermal & Wind Comfort: A literature review

This paper survey importance of urban open spaces and effective parameters on people attendance. In the recent years, low-quality environments have caused a low level of people attendance in that places and subsequently, lots of different problems in human life. One of the determining factors affecting the quality of the environment is providing human comfort. This paper discusses human comfort features. The aim of this article is presentation guidelines based on the creation of the wind and thermal comfort in urban open spaces. According to the fact, by the presence of comfort we can return people to urban open spaces. We derived some conceptual frameworks and categorized them on a chart. The table is divided into four climatic regions based on Iran climatology, to lead architects, urban planners for designing desirable spaces.

The environmental effects of aerodynamic interference between two closely positioned irregular high buildings

The close proximity of high buildings in urban areas causes significant interference effects to occur between them. Commonly, it has an adverse effect upon wind conditions in such areas. Taking into account the increasingly dense arrangement of buildings in cities, this problem will most likely become more significant in future years. Aerodynamic interference has been analysed in many research papers; however, it usually focusses only on the influence of particular variables on the phenomenon. This paper provides a more comprehensive approach, taking into account a case study of irregularly shaped tall buildings. Aerodynamic interference is considered in three aspects: mean pressure distribution on external surfaces, aerodynamic global forces and pedestrian wind comfort. Measurement results clearly show that the orientation of the interfering building and its surroundings with respect to wind direction is crucial for the effects of aerodynamic interference. It is also concluded that the close proximity of two buildings causes high values of negative pressure on walls facing a gap. Nevertheless, at the same time, the shielding effect of the interfering building decreases with regard to the global wind action on the analysed building.

Improving pedestrian level low wind velocity environment in high-density cities: A general framework and case study

An acceptable pedestrian level wind environment is essential to maintain an enjoyable outdoor space for city residents. Low wind velocity environment can lead to uncomfortable outdoor thermal experience in hot and humid summer, and it is unable to remove the pollutants out of city canyons. However, the average wind velocity at pedestrian level is significantly lowered by closely spaced tall buildings in modern megacities. To improve the low wind velocity environment at pedestrian level in high-density cities, a general framework and detailed guidelines are needed. This study is the first time to develop such a framework, and provide detailed guidelines for improving pedestrian level low wind velocity environment in high-density cities. Additionally, a detailed review and summarisation of evaluation criteria and improvement measures are presented in this paper, which provide additional options for urban planners. To investigate the performance of the framework, the Hong Kong Polytechnic University campus was utilised as a case study. Results showed that pedestrian level wind comfort was greatly improved with the developed framework. The outcomes of this study can assist city planners to improve the low wind velocity environment, and can help policy makers to establish sustainable urban planning policies.

Design for improving pedestrian wind comfort: a case study on a courtyard around a tall building

ABSTRACTWind has an important impact on pedestrian comfort around buildings. Wind around tall buildings may cause significant problems at the pedestrian level and requires analysis. Wind comfort analyses are conducted via computational fluid dynamics (CFD) simulations and wind-tunnel studies. Engineering solutions are crucial in addressing wind discomfort issues. However, such solutions should not be applied independently of the architectural context. A multidisciplinary approach can bridge the gap between architectural design and engineering wind-comfort solutions. Adopting such an approach, this paper presents a design strategy to mitigate wind discomfort in a courtyard around a tall building. The CFD simulation results indicate that the proposed design provides the required wind comfort levels according to the NEN 8100 standard. In addition, using CFD simulations in combination with the standard is demonstrated to be an efficient method for improving pedestrian wind comfort. This outcome can help guide future research on wind comfort and thus contributes to improving the environmental quality of urban areas.

Pedestrian-level wind conditions in the space underneath lift-up buildings

Lift-up buildings are advantageous in improving the wind circulation in a congested and compact city. However, the wind conditions in the void underneath a lift-up building, also known as the lift-up area, are vital for wind comfort of occupants of lift-up buildings. This study tested 28 lift-up buildings in a boundary layer wind tunnel to assess the influence of key design parameters; height and width of the main structure, and height, width, depth, and the shape of the central core on the wind conditions in the lift-up area. The results of the analyses show a significant influence of building height on the magnitude of wind speeds in the lift-up area while the width of the central core controls the area with low wind speeds. Tall buildings with short lift-up cores have small areas with acceptable pedestrian wind comfort, which can be increased by adopting corner modifications for the central core. The area of acceptable pedestrian wind comfort increases in oblique wind directions as the areas of high (>3.5 m s−1) and low (<1.5 m s−1) wind speeds are decreased. Finally, a non-linear second-order multivariable regression model is developed to predict pedestrian wind comfort in the lift-up area.

Effects of building height and porosity on pedestrian level wind comfort in a high-density urban built environment

Pedestrian level wind environment is affected by stagnated airflow in high-density cities. This study provides an understanding of the effects of building height and porosity size on pedestrian level wind comfort. The computational fluid dynamics (CFD) technique is utilized to reproduce wind flow around buildings at pedestrian level, and new wind comfort criteria for a low wind environment are adopted to evaluate wind comfort. More specifically, the Steady Reynolds Averaged Navier–Stokes (RANS) renormalization group (RNG) k–e turbulence model is employed in this study, and the accuracy of the simulation results are assured by validation against the wind tunnel test data. The influence of different building heights and porosity sizes on wind comfort around an isolated building and a group of buildings are subsequently examined. It is shown that an increase building height could improve wind comfort inside the site boundary for both the isolated building and group of buildings. Furthermore, the wind comfort benefits increased when porosity is on the first floor compared to when it is on the second floor. Moreover, larger porosity size generally results in better wind comfort than smaller porosity size. From a practical view point, this study provides information for city planners and architects to use in the improvement of pedestrian level wind comfort, without losing land use efficacy.

Wind comfort assessment by means of large eddy simulation with lattice Boltzmann method in full scale city area

Large-eddy simulations based on the Lattice-Boltzmann method of the flow in a realistic, full scale urban area are performed to compare several wind comfort criteria. It is observed that popular criteria for pedestrian comfort lead to very different conclusions, due to the access to high spatio-temporal resolution data. Different mixed strategies based on the combination of several criteria are proposed and compared to enhance pedestrian wind comfort assessment in practical cases.

Microclimate assessment method for urban design – A case study in subarctic climate

Interest in climate-sensitive urban design has grown in recent decades. Nevertheless, there are various difficulties associated with such an approach. One of these is the lack of simple comfort assessment tools. This article presents a method for microclimate assessment that is composed of a wind comfort analysis and a microclimate assessment based on measuring a combination of solar access and wind velocity. The study includes analysis of a proposed urban project situated in Kiruna, a Swedish town located in the subarctic region of the country. The results from the simulations were then overlaid to produce combined microclimate maps for three specific dates: winter solstice, spring equinox and summer solstice. The maps illustrate relative microclimate differences between areas in the proposed project based on combinations of wind/lee and sun/shadow conditions. The outcomes showed that only a small proportion of the area studied had favourable microclimate conditions at the winter solstice and spring equinox. The thermal comfort Index OUT_SET* was calculated for the summer solstice in the study area. Comparisons between the spatial distribution of OUT_SET* values and the microclimate assessment map showed a large degree of correlation. The method is intended to be a simple and representative evaluation of microclimate.

Large Eddy Simulation study on the structure of turbulent flow in a complex city

Large Eddy Simulation (LES) of atmospheric flows has become an increasingly popular modelling approach within the last years, as it has the potential to provide deeper insight into unsteady flow phenomena. LES can be improved and validated using specifically designed and well documented wind tunnel datasets. In this work, we evaluate the performance of LES against a wind tunnel experiment in a semi-idealized city (“Michel-Stadt”; CEDVAL-LES database) and use the LES results to study the structure of the turbulent flow at the particular urban area. The first, second and third order statistics are presented, as well as velocity frequency distributions and energy spectra. The results compare well with the experimental values. Information about special features of the flow field is also provided. A particular focus of this work is put on the influence of grid resolution on the results. Five different grids are examined and the required resolution for turbulent flow within the canopy layer is evaluated. This study reveals the strong potential of LES for urban flow simulations. It is shown that LES can assess highly non-Gaussian flow behaviour in street canyons, which has implications for urban ventilation, wind comfort assessment and urban design.

Assessment of pedestrian-level wind conditions in severe cold regions of China

Pedestrian-level wind environment in urban areas has a significant impact on the quality of urban dwellers' daily life. For pedestrian-level wind studies in severe cold regions, the cooling effect of wind and related thermal discomfort in winter is quite significant. However, thermal effects of wind are not considered in most wind comfort studies and wind comfort generally only refers to the mechanical effects of wind on people. Therefore, particular consideration is given to the chilling effect of wind on exposed skin and risk of frostbite in winter, and a wind chill criterion based on the wind chill temperature is proposed in this study. The pedestrian-level wind conditions in seven representative residential areas summarized from cities in severe cold regions of China are assessed based on the wind mechanical comfort criterion of NEN 8100 and the wind chill criterion. CFD simulations are performed to provide the pedestrian-level aerodynamic information, and the simulation results are validated by wind tunnel experiments. The assessment results show that the wind mechanical comfort or wind chill criterion need to be combined when assessing the wind conditions in severe cold regions. From the perspective of wind mechanical comfort and wind chill, the multi-storey residential areas with hybrid-type and the enclosed-type layout are recommended in severe cold regions. Moreover, a strict control of building height in residential areas is important to improve the pedestrian-level wind mechanical comfort, but not very helpful to reduce the occurrence of frostbite in winter.

Investigation of Pedestrian Comfort with Wind Chill during Winter

Two types of methods are used to evaluate pedestrian comfort: pedestrian wind comfort and outdoor thermal comfort. To accurately ascertain the outdoor wind environment, wind speed is the only parameter considered. However, pedestrians may still feel discomfort when the perceived temperature is low, even though the wind comfort criterion has been satisfactorily fulfilled. The purpose of this study is, therefore, to investigate pedestrian comfort when the perceived temperature is low, especially in winter conditions. To achieve this, a pedestrian survey was conducted, and 588 respondents completed a questionnaire. The results show that pedestrians feel discomfort when the WCET (Wind Chill Equivalent Temperature) is low, with almost 40 percent of respondents answering that they feel discomfort in these conditions. In conclusion, the threshold wind speed of the winter season could be determined to be lower than that of the existing comfort criteria by applying the WCET.

Application of a multi-variable optimization method to determine lift-up design for optimum wind comfort

The lift-up building design has been demonstrated to provide favorable wind comfort, but there is a lack of investigation on optimum wind comfort condition. This study coupled computational fluid dynamics (CFD) technique and response surface methodology (RSM) to determine the most desirable wind comfort around an isolated building with lift-up design. A multi-variable optimization method is proposed to determine optimum wind comfort and the corresponding lift-up design variables, namely, lift-up height (HL), core aspect ratio (AR) and core number (N). To better illustrate wind comfort around the building, the wind comfort in the lift-up area and the podium area are investigated separately. The Detached Eddy Simulation (DES) approach is employed throughout the whole CFD simulation process. The quality and goodness of the established RSM models are examined by analysis of variance and genetic algorithm is applied to generate optimal design solution. The generated results illustrate good performance of the established RSM model. Results show that the optimum wind comfort is obtained when HL is 8 m, AR is 10%, and N is 6. The lift-up core aspect ratio is subsequently found to have greatest effect on wind comfort among the three design variables in both the lift-up area and the podium area. In addition, the proposed method is applicable to other similar environmental design conditions and the outcomes of study can also be of great value in the improvement of wind comfort in compact urban cities.