Urban air mobility (UAM) is an emerging concept in air transportation featuring highly automated aircraft that are expected to include a mix of piloted, remotely piloted, and fully autonomous vehicles. The aim of UAM is to provide a wide range of services—intracity and intercity—including on-demand air taxis, air shuttles, cargo air vehicles, and medical emergency services.
With an ever-growing urban population around the world, cities and megacities will inevitably look at UAM as an alternative transportation mode to help reduce pollution levels, improve connectivity, and reduce strain on existing transport networks.
In the context of UAM, electric-powered vertical take-off and landing aircraft, known as eVTOLs, provide perfect mobility solutions for densely built-up urban environments. Despite the significant technological advancements made in the UAM industry in recent years, wind remains the most challenging natural physical phenomena confronting eVTOL aircraft.
Weather events as well as their complex interaction with cities and megacities have the potential to influence many aspects of UAM, including safety, operations and passenger comfort. Disruptions caused by strong winds, wind shear and turbulence can impact the operational down-time of eVTOLs, and the frequency of thunderstorm events could also dictate the financial viability of UAM operations in certain cities.
Generally, in urban environments, the building-induced hazards that arise from complex wind conditions near high-rise buildings will need to be taken into consideration during the planning stage of flightpaths and vertiport siting.
Integral to Planning and Operations
MODELLING AND SIMULATIONS
Within the modelling and simulation design space, advanced and extensive city-level as well as vertiport site-specific wind studies will be required—to quantify complex airflow patterns within the urban canopy, to assess the risk associated with atmospheric turbulence, and to assess the risk associated with proximity to high-rise buildings, particularly in relation to flight operations.
An initial assessment of city-level historical weather conditions—with a focus on the frequency of existing weather-related risks and their potential impact on operations and availability of service—will be crucial to support planning and inform investment decisions.
PREDICTIVE DESIGN TOOLS
Design tools such as boundary layer wind tunnel testing and cloud-based computational fluid dynamics (CFD) simulations will need to be employed to quantify the complex city- and vertiport-specific three-dimensional turbulent flow features that are inherent in the urban canopy of modern cities and megacities and to ensure that building-induced hazards are taken into consideration. Wind tunnel testing will rely on the use of flow measurement techniques such as particle image velocimetry (PIV), whilst CFD simulations will rely on scale-resolving simulations (SRS) such as large eddy simulation (LES) or detached eddy simulations (DES). The results of these predictive tools will need to be frequently updated to take into account that cityscapes are not static entities.
Data collected experimentally (wind tunnel testing) and numerically (CFD simulations) could also be used to drive motion simulation testing to obtain pilots/passengers feedback, determine practical turbulence thresholds for safe and comfortable flight operations and deliver vertiport-specific training to pilots.
Figure 1 and Figure 2 show some of the visual outputs that can be obtained from detailed DES simulations.