Pedestrian-level Wind Research Articles

Numerical evaluation of pedestrian-level wind and indoor thermal comfort of a historical monument, Muğla, Turkey

PurposeThe study aims to analyze both thermal and wind comfort conditions of a historical mosque's interior and outdoor spaces for the planning of further conservation decisions.Design/methodology/approachThe method is composed of two steps. First, thermal comfort analyses are conducted via Design-Builder Software. The predicted mean vote (PMV) and predicted percentage of dissatisfied indices were calculated and evaluated using the ASHRAE 55–2010 standard. Thermal comfort conditions are analyzed with the proposed three operations. Second, wind comfort analyses are conducted via computational fluid dynamics (CFD) software. Outdoor thermal comfort conditions are predicted by air temperature, mean radiant temperature, wind speed and relative humidity.FindingsThe (PMV) in the harim was calculated as −1.83 (cool) which corresponds to a predicted percentage of dissatisfaction (PPD) equal to 68.54%. Thermal comfort was provided by daytime and continuous operations; however, intermittent operations did not provide thermal comfort. The wind velocities around the mosque are well below the 5 m/s limit value for standing defined by NEN 8100 wind nuisance standard. Moreover, the limit value of 2.5 m/s for sitting was also satisfied with more than 80% of the semi-enclosed area around the entrance of the mosque. Last comer's hall remains in a slight cold stress range, the rest of the areas have no thermal stress.Originality/valueThis two-stage study creates a base for further improvements to provide comfort conditions in a historical building without interfering with its original features.

Pedestrian Wind Analysis for Indian Sub-Continent

Urbanization in India is causing local wind and climate changes near high-rise buildings, affecting the urban wind climate pedestrian-level winds to dangerous and uncomfortable levels. Hence, today's architectural planning Wind comfort has to not only consider the wind load and internal conditions, but also must consider the outdoor wind building design environment. This study reviewed the methods of evaluating pedestrian-level wind weather, different Wind tunnel test standards of wind comfort, and various techniques for evaluating pedestrian-level wind speed. In the CFD Numerical following section, a brief overview of the current research on this topic and the way forward in India is Modeling related to the design and configuration of windward buildings at the pedestrian level. After analysing the previous documents, the authors recommend it is very necessary to homogenize the various wind standards, as it might have different consequences for planers. Among the various wind tunnel experimental technologies, compared to the hot wire wind speed measurement method, the Irwin probe’s accuracy and simplicity is justified, and can be installed in multiple positions to measure wind speed horizontal of pedestrians at the same time. For the numerical simulation, several researchers have used the Renault medium Navier stokes-based technique, although the precision of this technique is not as good as the simulation of large eddies and the simulation of separate eddies. However, this technology is not only precise but also costs less due to its requirement of less computing resources.

A Brief Introduction to Academic and Educational Activities in Taiwan’s Wind Engineering Society

This paper reviews domestic activities in the wind engineering field in Taiwan for the past nine-year period from 2012 to 2021, including activities of the Taiwan Association for Wind Engineering (TAWE), the Chinese Institute of Civil and Hydraulic Engineering (CICHE), and other related organizations. Among these activities, the activity of code revision is the main theme held by TAWE. Wind researchers and engineers were called to form seven working groups responsible for different revision targets. Besides the code revision, workshops have been regularly held every year to promote wind engineering education not only for students but also for engineers, together with several publications on theories or practices. Among these working groups, a complementary comparison work for the evaluation of pedestrian level winds is also attached to this paper in the appendix. Although still under discussion, a first national standard for offshore wind turbines in Taiwan is attempted to announce in the coming year. Taiwan’s wind engineering society has provided professional advice to help the standard in a sound status and consistent with the current wind code for buildings.

Urban ventilation assessment with improved vertical wind profile in high-density cities – Investigations in nighttime extreme heat

Climate change and heatwaves challenge urban dwellers’ thermal comfort and health. In Hong Kong, more frequent and intensive extreme heat has been observed recently. This study uses Light Detection and Ranging (LiDAR) to observe vertical wind profiles and calibrate numerical simulation methods for urban ventilation assessment in nighttime extreme heat (i.e. hot nights (HNs)) at a high-density site. A cross-comparison is conducted to the characteristics between the observed HN-averaged wind profiles and commonly-used 24-h-period-averaged wind profiles in summer. The observation reveals a weaker wind environment in HNs than 24-h-periods, and the weakest condition is found in HNs during prolonged extreme heat where the impacts of weakened advection surpass enhanced thermal buoyancy. Furthermore, CFD simulations are conducted to evaluate the deviations on urban ventilation assessment caused by the lack of consideration of nighttime extreme heat when setting inlet wind profiles and site thermal conditions. In the simulation results, the 24-h-period-averaged wind profiles cause significant deviations on pedestrian-level wind speed and velocity ratio (empirical model (>45%); LiDAR observation (>20%)). Considerable deviations are found when unstable thermal stratification is ignored (>20%). Consistent deviations on vertical turbulent flow structures induced by the inexplicit coupling between thermal buoyancy and advection are found. The findings call for urgent attention to the wind conditions in HNs since they are most needed for releasing heat stress and urban overheating. It is recommended to include explicit buoyancy effects in both measurement and modeling works to optimize urban ventilation assessment for tackling extremely high-temperature and weak-wind conditions.

Comparing the effects of sun and wind on outdoor thermal comfort: A case study based on longitudinal subject tests in cold climate region

Sun and wind are important physical factors that influence outdoor thermal comfort. This study compared the impact of sun and wind on outdoor thermal sensation by analyzing 3546 samples of subject test data during a case study in a cold climate city Tianjin, China. The data was collected from subject tests conducted under air temperatures ranging from 3.8 °C to 35.2 °C (mean 20.2 °C), wind from 0 to 4.8 m/s (mean 0.6 m/s), mean radiant temperature 1.8 to 68.9 °C (mean 36.8 °C) in Tianjin, China. In this particular study, the sun was found to be a more significant factor than wind during the test. Standardized linear regression of the pooled dataset revealed that the contributions of air temperature, sun, wind, and humidity to thermal sensation were 56%, 29.4%, 8.8%, and 5.9%, respectively. When compared under different air temperature ranges, the effect of sun was more than two times greater that of wind. When the air temperature was in the range of 5–10 °C, solar exposure increased the thermal sensation by more than 2 units, but a reduction in wind speed had no observable effect on thermal sensation. When the air temperature was as high as 30–35 °C, increasing the wind by up to 2 m/s lowered the thermal sensation in the shade, but not in the sun. A summary of pedestrian level wind measured in real urban spaces in 28 previous studies indicated that urban spaces generally have low wind speeds, with the median value of mean wind speed of 0.8 m/s. The results of this study provide useful information for designs to creating comfortable urban open spaces.

Investigating the Effects of Urban Sidewalk Walls on Pedestrian Level Wind Comfort (Case Study: Tabriz City)

Investigating the Effects of Urban Sidewalk Walls on Pedestrian Level Wind Comfort (Case Study: Tabriz City)

Assessment of the Influences of Post-Construction Facilities on Pedestrian-Level Wind Environment: An Experimental Study in Changsha, China

Assessment of the Influences of Post-Construction Facilities on Pedestrian-Level Wind Environment: An Experimental Study in Changsha, China

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.

Impacts of building layout on pedestrian level wind comfort and gas pollutant diffusion

Introduction: The impacts of building layout on pedestrian level wind comfort and gas pollutant diffusion are simulated using computational fluid dynamics method. Materials and methods: The control equations of flow and pollutant diffusion are solved by using ANSYS Fluent. The SIMPLE algorithm is selected for the pressure-velocity coupling. The data from wind tunnel experiment at Tokyo Polytechnic University is employed in the validation case. Results: The velocity field and turbulence intensity at pedestrian level under different building layouts are obtained. The distribution and evaluation of wind comfort grade and pollutant concentration are given. Conclusion: Building layouts have significant impacts on flow and pollutant diffusion at pedestrian level. The outward staggered layout of building group can improve both wind comfort grade and air quality, but the inward staggered layout has the adverse effect. Non-staggered layouts are the worst in terms of the wind comfort grade in this paper.

Generic models for predicting pedestrian-level wind around isolated square-section high-rise buildings

High-rise buildings have significant effects on pedestrian-level wind in their vicinity, and are closely related to people's daily lives. The social implications of this problem have caused worldwide concern. Thus, an accurate and fast way for assessing the pedestrian-level wind environment has become increasingly important in the preliminary design of tall buildings. Some mathematical formulae for predicting pedestrian-level wind, referred to as generic models (GM), have been developed from experimental results. In this study, GMs reflecting the different contributions of physical causes, such as Type I (Slenderness) Effect and Type II (Height) Effect, on pedestrian-level wind are proposed and verified based on quantitative analyses and wind tunnel test results. The proposed GMs may be applied to assess pedestrian-level winds for various square-section high-rise and super-high-rise buildings, with widths from 25 m to 75 m, and heights from 60 m to 600 m.

Predicting wind flow around buildings using deep learning

The wind velocity field around buildings provides deep insights into the aerodynamic characteristics of buildings and indicates the pedestrian-level wind environment around buildings. Particle image velocimetry (PIV) is usually employed to measure the wind velocities around building models. Due to laser-light shielding, measuring instantaneous wind velocities at some shielded locations around a building model remains difficult. As a result, analyzing the wind flow pattern with these unmeasured wind velocities is difficult. Using machine learning techniques to impute unmeasured values allows for a comprehensive study of wind flow patterns with laser-light shielding. Unmeasured velocities around building models were imputed in this study using machine learning (ML) models such as the generative adversarial imputation network (GAIN), multiple imputations by chained equations (MICE), and neighbored distanced imputation (NDI). GAIN was the best model with a minimum variance and standard deviation of 1.508 and 1.228, respectively. Compared with experimental wind velocities, GAIN produced the minimum average mean squared error of 2.4%. The correlation between the experimental and predicted wind velocities was 98.2%. Thus, the validated GAIN model is recommended to be integrated into the PIV study to impute the unmeasured wind velocities to obtain a complete wind flow pattern.

A CFD study on the Irwin probe flows

Irwin probes are surface sensors commonly used to determine the shear stress in near-wall regions, by calibration of related pressure signals. These devices have been widely used in wind tunnel studies dealing with pedestrian-level wind conditions. In this work, three-dimensional Computational Fluid Dynamics (CFD) simulations are performed to characterize the complex flow field and pressure distribution developed around and within the Irwin probe, at three distinct low-Reynolds number regimes. The emergence of coherent flow structures past the sensor is categorised and preventive spacing intervals, necessary to mitigate mutual interference, is numerically evaluated. The computations corroborate the original spacing recommendations by Irwin. For typical operation conditions, long streamwise tip vortices are observed in the wake of a single sensor. In addition, the predictions suggest the existence of a low-Reynolds number threshold, below which such structures are supressed, resulting in diminished interference effects. Numerical results also suggest a nearly uniform axial pressure distribution and place in evidence very interesting flow field characteristics.

Impact of surrounding environments and vegetation on wind comfort assessment of a new tower with vertical green park

Modern architectural concept of “vertical forest” boosts the tendency of including permeable and green spaces in buildings and its surroundings. However, whilst green spaces generally make buildings and cities more ecofriendly, it is insufficiently known to which extent the surrounding environment and the vegetation may positively or negatively influence the pedestrian-level wind comfort quality of buildings amidst historical and well-settled urban layouts. This was the scope of the present study for which wind-tunnel (WT) testing and 3D RANS simulations were performed on two facing towers in Medellìn (Colombia), in order to (i) investigate the wind field and the pedestrian-level wind comfort around the towers; (ii) to compare the performance of WT and 3D RANS for wind comfort analysis; (iii) to evaluate the impact of the environment surrounding the two towers and (iv) the mitigation effects of vegetation on wind comfort. WT tests were performed on a scaled model (1:250) without surrounding, for 12 wind directions and 3 sets of measurement positions. The same case study without (i.e. CFDs) and with (i.e. CFDd) surrounding environment was simulated by 3D RANS. Next, an implemented CFDd case including vegetation (i.e., CFDd-V) was simulated for three LAD values. Overall, the surrounding had a significant impact on wind comfort assessment. The CFDd case showed a better-quality class than WT and CFDs. The CFDs and WT case showed a satisfactory agreement and the similar comfort quality class. The vegetation provided a remarkable improvement of comfort quality class mainly for set 1 and 2.

The Influence of Wind Effects on Architectural Buildings Heights in Iraqi Residential Buildings Based on Computational Fluid Dynamics Simulations

The gradient of height in buildings is the most common way to prepare a comfortable environment and to increase wind forces around the buildings. This study assessed various design choices that enable architectural buildings to have different heights using computational fluid dynamics (CFD) simulation to analyse wind conditions. Nonetheless, wind effects may create uncomfortable zones around high buildings and may be hazardous for pedestrians in open spaces. As such, this study looked into pedestrian level wind (PLW) to enhance the wind environment of buildings in Iraqi climate. Wind characteristics may create a range of disturbance levels that affect pedestrian areas. Iraqi residential buildings were taken as case study to quantitatively analyse the outdoor buildings at PLW, so as to generate some ideas and solutions between CFD simulation analysis and architectural design to yield an optimal model.

Improving local pedestrian-level wind environment based on probabilistic assessment using Gaussian process regression

Many wind comfort assessment standards have been proposed to evaluate wind comfort and safety in spaces with intended use for pedestrians, such as pathways, building entrance areas, amenity spaces, and outdoor sitting spaces. However, the optimization of the wind environment presents a unique combination of complexities in assessment, simulation, and design. Conventionally, designers rely heavily on wind tunnel experiments or computational fluid dynamics simulations based on which only limited proposals are examined to select the one with the best wind performances. A new design framework for proactively improving the wind conditions at various measuring positions is demonstrated in this paper. Gaussian process regression models are combined with the Latin hypercube sampling method to approximate the relationships between design variables and wind velocities at discrete locations. Gaussian process regression is a non-parametric model well-suited for modeling the non-linear and stochastic wind behaviors. Moreover, it can provide the prediction mean and variance, and the latter is incorporated into a prediction quality function to quantify the modeling uncertainty. In the case study, with the objectives of maximizing the winter and summer wind comfort and minimizing the modeling errors, the robust and near-optimal designs of a target building in an infill development project are explored using the evolutionary search algorithm. We believe that this framework can be migrated to other urban design practice to better predict and simultaneously optimize the microclimate performances at locations of interest, such as solar access, indoor ventilation efficiency, and thermal comfort.

Improved urban heat island mitigation using bioclimatic redevelopment along an urban waterfront at Victoria Dockside, Hong Kong

Bioclimatic design provides solutions to mitigating the urban heat island (UHI) effect and improving urban quality of life. Waterfront settings provide a unique opportunity for UHI mitigation, as cool winds (i.e. sea breezes) provide good cooling conditions. We used ENVI-met numerical simulations to investigate the synergistic mitigation effects of redeveloped urban forms, ventilation corridors, and extensive greenery on local microclimate and outdoor thermal comfort at an urban waterfront in Victoria Harbour, Hong Kong. The thermal performance along the waterfront and within an inner urbanised area was evaluated in three scenarios: existing configuration (Case A), redeveloped building form (Case B), and Case B with a ventilation corridor and extensive greenery added. In the study area's subtropical climate, the additional strategies used led to a synergistic improvement in microclimate and thermal comfort in both settings. The appropriate use of combined urban forms and ventilation corridors along waterfronts can thus lead to a more acceptable pedestrian-level wind environment and enhance the ventilation potential within inner urbanised areas. The cooling intensity of greenery (turf and green facades) along such waterfronts can also be extended for further benefits. Overall, the synergistic mitigation effects of redeveloped urban forms, ventilation corridors, and extensive greenery in proximity to water bodies demonstrated here provide science-based guidance for the use of bioclimatic design along urban waterfronts in order to achieve improved microclimates and thermal comfort at neighbourhood scales.

Multi-fidelity shape optimization methodology for pedestrian-level wind environment

In this study, a multi-fidelity shape optimization framework is proposed for the pedestrian-level wind environment (PLWE). In the proposed framework, low-fidelity computational fluid dynamics (CFD) models based on steady Reynolds-averaged Navier–Stokes equations (RANS) models and high-fidelity CFD models based on large-eddy simulation (LES) are efficiently integrated into the optimization process to improve the optimization reliability while maintaining its computational speed in an affordable range for practical engineering applications. The optimization solver is coupled with an approximation model generated by low-fidelity CFD samples obtained using a design of experiments (DOE) technique. The optimal candidates are then evaluated according to the degree of improvement of the objective function compared to the reference case. If the degree of improvement shows significant deviations between the low-fidelity and high-fidelity models, suitable corrections and modifications are applied to improve the reliability of the optimization process. The applicability of the proposed method was investigated in terms of minimizing the high-wind-speed area, as the optimization objective, around a high-rise building considering (a) uniform urban blocks and (b) real urban blocks with different frequency distributions of wind directions associated with two different local wind climates. In summary, a significant reduction in the critical strong-wind area around the target building was realized using the proposed optimization framework. Furthermore, the application of the proposed multi-fidelity optimization framework highlighted the importance of considering the local wind climate in architectural design.

Hybrid framework for rapid evaluation of wind environment around buildings through parametric design, CFD simulation, image processing and machine learning

High-efficient evaluations of building performance are often required for comparisons of different design alternatives in architectural sustainable design processes. General Computational Fluid Dynamics (CFD) simulations are usually complicated and time-consuming for wind environment investigation and evaluation. A hybrid framework for rapid evaluation of pedestrian-level wind environment will be proposed in the present work. This framework will then be formulated by integrating parametric design, CFD simulation, image processing, and machine learning, and it could immediately predict the Low-Velocity Areas (LVAs) around rectangular-form buildings. A large amount of data of 300 building cases generated by parametric design, CFD simulation, and image processing to train a Machine Learning Model (MLM) could be applied for the prediction of LVAs. In the case investigations, MLM was tested in the prediction of the other new 24 building cases with random geometric parameters. The comparison of MLM and CFD results showed that their solutions were close to each other. Efficiency and accuracy of the hybrid framework were further demonstrated through quantitative analysis of statistical discrepancies of MLM and CFD results. Hybrid framework was an original attempt to integrate multiple emerging computational tools, and it could provide high-efficient quantitative analysis of wind environment and give practical design optimization information in the early stage.

Flow field around two tandem non-identical-height square buildings via LES

Although the study of flow around buildings has a rich background, the development of construction material, the congestion of buildings, the urban ventilation and consideration of pedestrian wind condition make the necessity of further insightful flow-physic studies. This study numerically investigates the gap and wake flows associated with two inline non-identical-height (aspect ratios of 4 and 7 for the up- and downstream) buildings at a Reynolds number of 2.2 × 104 and gap spacing (G*) of 1, 3, and 5 through the large eddy simulation technique. It is found that an increase of G* mostly affects the flow pattern in the gap, so that the slender-body, alternate reattachment and semi-stable gap flow at the G* of 1 (or 3) turns into the co-shedding flow at the G* of 5. The pressure coefficients (C¯p) on the cylinders' faces show that an increase of G* from 1 to 3 increases/decreases the C¯p on the side (and top) faces of upstream/downstream cylinders, respectively. Further increasing G* from 3 to 5, however, drops the C¯p on the side and top faces of both cylinders. On the other hand, the flow regime produces a profound effect on the pedestrian level so that the strong wind condition appears in the small gap, and a very weak wind condition in the vortex cores. Hence a minimum gap of 3 is recommended for better pedestrian level wind conditions. Besides, increasing gap from 1 to 5 reduces the shielding effect of the interfering building markedly.

Application of artificial intelligence to urban wind energy

Optimal implementation of urban wind energy contributes towards the development of sustainable cities. This paper focuses on generating an adequate database to use with artificial intelligence (AI) tools to improve the generation of urban wind energy. The paper presents wind tunnel results for square, rectangular, U-shaped, T-shaped, L-shaped buildings and some measurement points in various city configurations. Moreover, the effect of building shapes on turbine street level locations was elaborated using validated CFD literature results on pedestrian level wind conditions. Using these results and literature review from the past decade, a decisional flow chart approach was developed, allowing a preliminary assessment of the modification of upstream wind velocities due to urban parametric conditions. Expert and artificial neural network (ANN) systems were built and tested on city configurations with their results compared with those from wind tunnel measurements. The ANN system shows better predictive values than the expert system, with up to 99% success rate. AI programs with the decisional flow chart approach may be used for the identification and assessment of potential turbine locations to maximize the production of urban wind energy.