SimScale introduces and explains how its capabilities can be extended to simulate outdoor thermal comfort, to ultimately mitigate the urban heat island effect.

"Thermal comfort" is a concept most often applied to the indoor environment. Many types of buildings will have their thermal comfort calculated under various climatic and occupancy conditions during the design stage and, more increasingly, measured during a building’s operation. The concept of thermal comfort, however, is increasingly being applied to outdoor environments and is often referred to as outdoor thermal comfort. Fortunately, it is also possible for designers to simulate outdoor thermal comfort using the CFD capabilities within SimScale and assess the heat island effect in cities.

The built environment has many environmental factors/variables that need consideration when designing buildings and cities. A city will be subject to uneven heating and cooling as the sun rises and sets, depending on its built form and skyline. Some urban areas will be shaded, while others are fully subjected to heat gain from the sun, leading to convective air currents that impact the local microclimate. Wind profiles in urban areas are artifacts of many aerodynamic and atmospheric forces, from surface roughness to turbulence caused by urban canyons; these factors tend to be transient phenomena and are difficult to predict. They require mathematical modeling to understand their behavior and interaction with their respective built environments. An urban heat island (UHI) is the adverse effect on outdoor thermal comfort caused by warmer temperatures observed in urban spaces and is a construct of several environmental variables, including air temperature, solar radiation, humidity and the wind. 

Universal Thermal Comfort Index (UTCI) plot in Ladybug using SimScale wind simulation results.

Simulating buildings and cities has historically required a high investment of time and money to provide accurate results. Novel CFD solvers such as the lattice Boltzmann method (LBM)-based Pacefish® have reduced simulation times from weeks/days to hours/minutes and run on GPUs to allow:

• Fast and accurate simulations
• GPU accelerated computing on the cloud (no need for local hardware)
• Scalability–model buildings to entire cities 
• Easy accessibility through any preferred web browser
• Online project collaboration
• Multiple-scenario analysis using parallel simulation capabilities

Ultimately, these cloud-based engineering developments mean that simulating the UHI in buildings and large city-scale projects is not only possible, but can be completed faster than ever before made possible with the new generation of CFD solvers at SimScale. This white paper (available for download below) shows how designers can use the powerful simulation features in SimScale to accelerate the calculation of the Universal Thermal Comfort Index (UTCI), a commonly used metric for assessing outdoor thermal comfort. 

Click here to download the white paper, "Simulating Outdoor Thermal Comfort."