Gusts Encountered by Flying Vehicles in Proximity to Buildings

Abstract

There is a growing desire to operate Uncrewed Air Vehicles (UAVs) in urban environments for parcel delivery, and passenger-carrying air taxis for Advanced Air Mobility (AAM). The turbulent flows and gusts around buildings and other urban infrastructure can affect the steadiness and stability of such air vehicles by generating a highly transient relative flow field. Our aim is to review existing gust models, then consider gust encounters in the vicinity of buildings as experienced by flight trajectories over the roof of a nominally cuboid building in a suburban atmospheric boundary layer. Simplified models of fixed- and rotary-wing aircraft are used to illustrate the changes in lift and thrust experienced by flight around the building. The analysis showed that fixed-wing aircraft experienced a substantial increase in angle of attack over a relatively short period of time (<1 s) as they fly through the shear layer at a representative forward velocity, which can be well above typical stall angles. Due to the slow flight speeds required for landing and take-off, significant control authority of rotor systems is required to ensure safe operation due to the high disturbance effects caused by localized gusts from buildings and protruding structures. Currently there appears to be negligible certification or regulation for AAM systems to ensure safe operations when traversing building flow fields under windy conditions and it is hoped that the insights provided in this paper will assist with future certification and regulation.

Review of Wind Flow Modelling in Urban Environments to Support the Development of Urban Air Mobility

“…Several papers that investigate gust loads on UAM aircraft were seen to use the traditional von Kármán and Dryden models for simulating gusts; however, the urban built environment would violate many core assumptions made within these models [94,105]. Thus, low-altitude turbulence flow field generating software such as TurbSim is seen to be used to assess flight responses of different-sized quadcopters [91].…”

“…Likewise, ref. [94] provides a detailed description of the effects of gusts on fixed-wing UAVs operating close to obstacles, and a case study of the effects of gusts on UAM operations with the help of a CFD-based wind model from [59].…”

Integrating Electric Vertical Takeoff and Landing Aircraft into Public Airspace: A Scenario Study

“…Surface winds in the Detroit area can reach 30 to 40 knots with gusts, which can displace, or damage aircraft left unsecured in the open. Rooftop flow conditions and turbulent windshear patterns near tall buildings add complexity to eVTOL aircraft performance requirements, especially for takeoff and landing [57].…”

Shoulder viscoelasticity in a raptor-inspired model alleviates instability and enhances passive gust rejection

“…Atmospheric disturbances such as gusts and turbulence are routinely negotiated by birds, and their evolution confers a myriad of possible coping strategies across a spectrum of passive preflexes and sensorimotor control [1][2][3][4][5][6]. For small uncrewed aerial systems (UAS), however, traditional designs leveraging the simplicity of rigidity and decades of optimal aeronautical insight are often accompanied by fragile gust and turbulence response [7][8][9]. Research concerning UAS gust mitigation is therefore a vibrant and important area of inquiry [10][11][12][13] and has also emerged as a possible means for UAS-based kinetic power generation [14][15][16].…”