External Flow Around Tall Buildings (Transient Solver) — ANSYS Fluent CFD SimulationDescriptionThis project uses ANSYS Fluent to simulate wind flow through a domain containing three tall buildings that act as flow barriers — a representative example of the common "flow-around-obstacle" problems found throughout wind engineering (buildings, wings, propellers, and rigs all belong to the same family). A horizontal airstream enters the domain and interacts with the buildings, letting you examine how the wake develops behind each structure and how vortices form in their lee. As the opening project of the Urban Microclimate: All Levels CFD Training Package, it establishes the external-aerodynamics foundation of urban wind flow — the bluff-body behavior that underlies pedestrian wind comfort, building loads, and pollutant dispersion — before any pollutants are introduced.MethodologyThe 3D geometry, built in DesignModeler, is a large rectangular region of 120 m × 300 m × 100 m containing three buildings, each 75 m tall. Meshing in ANSYS Meshing is unstructured with 128,893 elements, with local refinement near the building surfaces for accuracy. The analysis is transient — run over 1 s with a 0.01 s time step — and solved with a pressure-based approach. A horizontal airstream of 5 m/s enters the domain and interacts with the buildings, with the transient setup capturing the unsteady wake and vortex behavior that a steady solution would miss.AnalysisThe results include pressure and velocity contours, turbulent kinetic energy (TKE), pathlines, and velocity vectors. The highest pressure occurs on the windward faces, where the flow first impinges on the buildings, while vortices form in the leeward wakes behind them. All reported fields are evaluated at the final simulation time (t = 1 s). From these results you can assess the wind loading on the building faces, trace the wake structure and vortex shedding between and behind the buildings, and understand the flow patterns that govern wind comfort and dispersion in the built environment. By the end of this project, you'll be able to set up a transient external-flow simulation around bluff bodies, apply local mesh refinement near solid surfaces, and interpret the pressure, velocity, and turbulence fields that characterize urban wind flow.

External Flow Around an Atrium — ANSYS Fluent CFD SimulationDescriptionThis project presents a complete CFD simulation of the external airflow around a building atrium — a structure rooted in ancient Roman architecture and reborn in modern multi-story buildings as a glass-roofed space used for daylighting and natural ventilation. Atriums rely on two fundamental natural phenomena — the greenhouse effect and the chimney effect — and understanding the airflow around them is the first step in designing them effectively. At the urban scale, this kind of external-flow analysis matters because the wind around large buildings shapes pedestrian comfort, natural ventilation, and how structures interact with the surrounding built environment. Within the Urban Microclimate: All Levels CFD Training Package, this project builds on the tall-buildings case, applying external-flow analysis to a single architectural structure and establishing a reusable building-aerodynamics workflow.MethodologyThe 3D external-flow domain (3.35 m × 2.21 m × 3.9 m) is designed around the atrium structure in Design Modeler, then meshed in ANSYS Meshing with a refined unstructured grid of roughly 1.95 million elements — with finer cells near the building walls for accurate boundary-layer resolution. A pressure-based, steady-state solver suited to external aerodynamic problems is configured with the RNG k-ε turbulence model and standard wall functions — a combination well-suited to the separated and recirculating flows that form around bluff bodies. The external-flow boundary conditions are an 8 m/s velocity inlet, a 0 Pa gauge pressure outlet, and stationary walls. Pressure–velocity coupling uses the SIMPLE scheme with second-order discretization for pressure and momentum, and the domain is initialized with atmospheric pressure (101,325 Pa) and a uniform freestream velocity.AnalysisPost-processing generates 2D and 3D contours of pressure and velocity, pathlines, and velocity vectors on the XY plane, along with the pressure distribution over the building's wall surfaces. These results reveal how the 8 m/s wind interacts with the atrium walls — generating regions of high pressure, flow separation, recirculation, and acceleration around the structure. External flow analysis of this kind is a backbone of modern architectural and urban engineering, informing decisions about façade design, pedestrian wind comfort, natural ventilation, and structural wind loading. By the end of this project, you'll have a reusable external-flow workflow — designing the domain, refining the mesh near the walls, configuring the solver and turbulence model, and interpreting the pressure and velocity fields — that you can apply to virtually any external building-flow problem in the built environment.

Air Pollution within a Street Canyon — ANSYS Fluent CFD SimulationDescriptionThis project simulates pollution diffusion in a street canyon using ANSYS Fluent. When two rows of building blocks stand parallel to each other, the space between them forms what is known as a street canyon (or urban canyon) — a configuration whose geometry strongly influences how urban heat and airborne gases are distributed. This project investigates the amount and distribution of pollutants within that canyon space. Within the Urban Microclimate: All Levels CFD Training Package, this project introduces pollutant dispersion through the classic street-canyon geometry, applying the Species Transport model to the fundamental unit problem of urban air quality.MethodologyThe three-dimensional model is designed in Design Modeler, with a computational area 36 m long, 24 m wide, and 8 m high containing two rows of simple building blocks parallel to each other. To reduce computational cost, the model is limited in extent and symmetry boundary conditions are applied around the urban area. Meshing in ANSYS Meshing produces 1,938,659 elements. The Species Transport model is used to represent the two gaseous species — air and pollutant — where the pollutant has a specific heat capacity of 1100 J/kg·K and a molecular weight of 77.49064 kg/kmol, and air has 1006.43 J/kg·K and 28.966 kg/kmol. All pollutants are assumed to be generated within the canyon: two grooves in the ground act as the pollution source, with a source term of 0.011 kg/m³·s. Initially only air fills the domain, and pollutants then begin to be produced. At the inlet, pure airflow enters through a velocity-inlet condition whose magnitude varies with the inlet location — implemented as a profile in UDF format — with the air temperature set to 300 K. The RNG k-epsilon model and the energy equation are enabled to resolve the turbulent flow and the temperature field.AnalysisAt the end of the solution, three-dimensional contours of pressure gradient, velocity, temperature gradient, air mass fraction, and pollutant mass fraction are obtained, along with two-dimensional contours of velocity, air mass fraction, and pollutant mass fraction. The results show air pollution originating from the interior of the street canyon, and the two- and three-dimensional velocity vectors reveal a vortex — a rotation of the flow — forming inside the canyon, which governs how the pollutant is trapped or cleared. By the end of this project, you'll be able to set up a Species Transport simulation with a ground-level pollution source, apply a UDF velocity profile at the inlet, and interpret the concentration and velocity fields that characterize air quality in a street canyon.

Pollution of the Street between Buildings — ANSYS Fluent CFD SimulationDescriptionMotor vehicles are a significant source of air pollution, producing carbon dioxide, carbon monoxide, hydrocarbons, nitrogen oxides, particulate matter, and a range of mobile-source air toxics. The health risks associated with living close to roads are linked less to PM2.5 mass — only slightly elevated near roads — than to pollutants such as ultrafine particles, carbon monoxide, NO₂, black carbon, and polycyclic aromatic hydrocarbons, which are markedly higher near traffic. This project uses ANSYS Fluent to simulate pollution in a street placed between two buildings. Within the Urban Microclimate: All Levels CFD Training Package, this project extends pollutant dispersion to a realistic street configuration with buildings of differing size, building on the idealized canyon toward more representative urban layouts.MethodologyThe geometry is a 3D rectangular domain measuring 40 m × 20 m × 25 m in the X, Y, and Z directions, containing two buildings: the first 3 m × 3 m × 15 m and the second 3 m × 10 m × 15 m in the X, Y, and Z directions. The geometry is created in Design Modeler, and ANSYS Meshing generates 274,496 structured elements. The simulation is steady and uses a pressure-based solver, appropriate for the incompressible working fluid, with gravitational acceleration included at 9.81 m/s² in the negative Y direction. The Species Transport model is used to solve for the pollution rising from the street.AnalysisAt the end of the solution, two-dimensional contours of pressure, velocity, and the volume fractions of pollution and air are obtained, with the contours viewable at intervals through the solution. The static pressure is high on the left (windward) side of the buildings, while the velocity rises as the flow passes over their tops; the pollutant volume fraction tends toward the left building side, carried by the airflow moving between the buildings. The average static pressure at the inlet is plotted as a convergence criterion. By the end of this project, you'll be able to set up a steady Species Transport simulation of traffic pollution between buildings, account for gravity in the dispersion, and interpret the pressure, velocity, and pollutant-fraction fields around a real street configuration.

Pollution in a Real Urban Zone — ANSYS Fluent CFD SimulationDescriptionUrban environments are the most important context of daily life, and in many developing countries air-quality conditions worsen year on year, even as technology reduces per-vehicle emissions — because transportation demand keeps rising. This project uses ANSYS Fluent to calculate how carbon dioxide from car exhaust is dispersed across an urban zone, using the Species Transport model to solve a transport equation for each component of the pollutant mixture. The purpose is to investigate the effect of free airflow on the CO₂ produced by traffic within a real city-street setting. Within the Urban Microclimate: All Levels CFD Training Package, this project scales pollutant dispersion up to an urban complex of multiple building blocks, representing the district-scale air-quality problem.MethodologyThe three-dimensional model is drawn in Design Modeler as a set of structural elements — several building blocks and a street belonging to a city — enclosed within a rectangular domain of 9 m × 13 m × 4 m around the urban complex. The airflow inlet is selected on three lateral faces of the domain, and a 0.1 m high area on one of the city streets acts as the CO₂ source, with a carbon-dioxide production rate of 4 kg/m³. Meshing in ANSYS Meshing is unstructured with 4,137,570 elements, refined near the internal boundaries for higher accuracy. Because both air and CO₂ are modeled, the Species Transport model is used, and the solver is pressure-based. The simulation is transient, since the goal is to study how the CO₂ concentration changes over time. Free airflow enters at 0.2 m/s and 300 K with zero CO₂ mass fraction; the outlet is a pressure outlet at 0 Pa gauge; and the walls are stationary with zero heat flux. Turbulence uses the standard k-epsilon model with standard wall functions, the energy equation is on, pressure–velocity coupling uses SIMPLE, and the solution is initialized with the standard method.AnalysisAt the end of the solution, two-dimensional contours of pressure, temperature, velocity, and air and CO₂ mass fraction are obtained across the whole model in the XY and YZ sections, along with three-dimensional contours of the same quantities in the region of the CO₂ source. These fields show how the free airflow transports and dilutes the emitted CO₂ across the urban zone and around the surrounding building blocks. The project includes the geometry and mesh file and a comprehensive training movie demonstrating the full solution and result extraction. By the end of this project, you'll be able to set up a transient Species Transport simulation on an urban complex, define a street-level CO₂ source, and interpret the concentration fields that reveal how effectively an urban zone ventilates traffic emissions.

Urban Heat Island (UHI) CFD Simulation on a Real Urban Zone, ANSYS Fluent TrainingDescriptionThis project simulates airflow and heat transfer over a real urban area — the Auckland University of Technology (AUT) campus in Auckland, New Zealand — to study the Urban Heat Island (UHI) effect using ANSYS Fluent.Urban heat island and pedestrian comfort are central concerns in urban planning. As cities grow denser and taller, buildings reshape local wind patterns and trap heat, creating uncomfortable or even unsafe conditions at street level. CFD lets planners predict wind speed and temperature around a real building layout while the design is still on the drawing board, so problem areas can be identified and fixed before anything is built.The study has two goals: to map pedestrian wind comfort and flag locations where wind speed exceeds 3.8 m/s, and to check outdoor thermal comfort, where the aim is to keep the campus area below 295 K.The real building footprints were extracted from Google Earth Pro, and the corresponding geometry and building volumes were reconstructed in ANSYS Design Modeler as a main domain (the campus itself) surrounded by a larger subdomain that captures the incoming wind.Simulation MethodologyThe analysis is carried out in two parts: wind comfort and thermal comfort.For the wind-comfort study, note that Auckland's airflow is predominantly from the southwest, shifting toward the northeast in summer as the high-pressure belt moves south, and that coastal areas are consistently windier than sheltered inland ones. Using representative wind conditions for the site, the model resolves the wind field around the buildings and evaluates it against standard pedestrian wind-comfort criteria.For the thermal-comfort study, solar loading is applied with the Discrete Ordinates (DO) radiation model, set from the site's geographic coordinates for mid-February at 1 p.m. The building surfaces are assigned a representative heat flux, the ground surface is fixed at 286.15 K, and the incoming free-stream air is set to 288.15 K, based on local meteorological data. Together these drive the temperature field that forms the urban heat island.Results & ConclusionThe velocity contours show that buildings directly exposed to the wind experience speeds up to about 30 km/h (≈ 8.3 m/s) at some points, well above the pedestrian-comfort limit. As the air moves into the passages between buildings it slows to around 10 km/h (≈ 2.8 m/s), which is comfortable, and it is damped further in the rear rows of buildings.On the thermal side, the incident solar radiation over the domain ranges from about 1560 to 1700 W/m²; taller buildings absorb more, while the passages between them receive less because of shading. Temperature contours were extracted at several heights above the ground: at 0.5 m the average is about 287.46 K with a local peak of 295.77 K, at 1 m the average rises to 287.96 K (peak 292.58 K), at 1.5 m the field changes little, and at 2 m the peak reaches 294.87 K. The warm zones between buildings come from heat rejected by the surrounding surfaces — the signature of the urban heat island — and one low but wide building (the meeting hall) cools more slowly and holds the highest roof temperatures.Overall, the wind-comfort criterion is exceeded in several exposed areas, particularly toward the suburbs, so the study points to mitigations such as windbreaks or added vegetation and greater spacing between closely packed buildings to avoid narrow, high-speed street canyons. The thermal-comfort target of 295 K is met across almost the entire campus at pedestrian height, with only a small, localized area reaching it, so heat is not expected to cause meaningful hardship for people using the campus.