Digital twins for cities emerge as tools to assist urban planning of cities. The digital twin of a city is generally made up of a three-dimensional model, sensors located throughout the city, and a collaborative data platform with information of all kinds (demographics, weather, traffic, infrastructures, etc.). The final objective is the use of this tool as a virtual laboratory to support urban planning, city management, decision-making, the adoption of new technologies, the prediction of breakdowns or the response to emergency situations. According to some estimates, 500 cities are expected to use digital twins by 2025.

One of the contributions that nablaDot can make to these digital twins is the modeling and prediction of the wind in a city. The wind within a city is difficult to characterize. Interaction with the built environment causes high turbulence, recirculation, local accelerations or low speed zones. What is the use of having detailed wind data in a city? The applications are many; some examples are the adaptation of urban planning to wind flows, the development of strategies for the mitigation of pollution and the improvement of air quality, the analysis of extreme events and the determination of risk zones, the support to structural design (calculation of forces on buildings, photovoltaic modules, singular structures), the elaboration of natural ventilation strategies in buildings, the planning of outdoor activities, the study of cooling in infrastructures (telephone masts), the installation of small wind turbines or the creation of wind maps for new means of air transport in cities (drones).

The simulation of wind in cities is complex and requires a proper use of advanced fluid simulation techniques. The representation of the geometry of the buildings, the computational meshing, the input conditions or the choice of turbulence models will have a significant influence on the results obtained. However, as time goes by, this sort of simulations are more affordable. Thus, we hope that in the coming years this type of simulation will become more and more common. Progress in digitization will also lead to the use of new calculation techniques, which, properly used, will provide more information and of higher quality than current techniques.

As an example of the affordability of carrying out the wind simulation in cities, we show next an example of an emblematic square of our city, the ‘Plaza del Pilar’. A few years ago, performing this simulation was unfeasible due to the cost required to obtain the parameters of the geometry of this plaza. Today, such geometry can be easily obtained, and perhaps it will be even more precise in a short period of time.