Flight-Relevant Gusts: Computation-Derived Guidelines for Micro Air Vehicle Ground Test Unsteady Aerodynamics

Abdel‐Rohman, Mohamed; Watkins, Simon; Ol, Michael V.; Jones, Anya R.

doi:10.2514/1.c035920

Cited by 17 publications

(6 citation statements)

References 24 publications

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“…In addition, CFD models could be used to thoroughly explore the gapped wing design space, enabling more rapid prototype iterations and optimization. CFD models and prototypes could also help evaluate the gapped wing control surface as a method of turbulence mitigation or gust alleviation [48][49][50][51][52][53].…”

Section: Limitations and Future Workmentioning

confidence: 99%

Avian whiffling-inspired gaps provide an alternative method for roll control

Sigrest

Inman

2022

Bioinspir. Biomim.

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Some bird species exhibit a flight behavior known as whiffling, in which the bird flies upside-down during landing, predator evasion, or courtship displays. Flying inverted causes the flight feathers to twist, creating gaps in the wing’s trailing edge. It has been suggested that these gaps decrease lift at a potentially lower energy cost, enabling the bird to maneuver and rapidly descend. Thus, avian whiffling has parallels to an uncrewed aerial vehicle (UAV) using spoilers for rapid descent and ailerons for roll control. However, while whiffling has been previously described in the biological literature, it has yet to directly inspire aerodynamic design. In the current research, we investigated if gaps in a wing’s trailing edge, similar to those caused by feather rotation during whiffling, could provide an effective mechanism for UAV control, particularly rapid descent and banking. To address this question, we performed a wind tunnel test of 3D printed wings with a varying amount of trailing edge gaps and compared the lift and rolling moment coefficients generated by the gapped wings to a traditional spoiler and aileron. Next, we used an analytical analysis to estimate the force and work required to actuate gaps, spoiler, and aileron. Our results showed that gapped wings did not reduce lift as much as a spoiler and required more work. However, we found that at high angles of attack, the gapped wings produced rolling moment coefficients equivalent to upwards aileron deflections of up to 32.7° while requiring substantially less actuation force and work. Thus, while the gapped wings did not provide a noticeable benefit over spoilers for rapid descent, a whiffling-inspired control surface could provide an effective alternative to ailerons for roll control. These findings suggest a novel control mechanism that may be advantageous for small fixed-wing UAVs, particularly energy-constrained aircraft.

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Section: Limitations and Future Workmentioning

confidence: 99%

Avian whiffling-inspired gaps provide an alternative method for roll control

Sigrest

Inman

2022

Bioinspir. Biomim.

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“…As the size, mass and speed of aircraft decrease, the susceptibility to turbulence and gusts increases [6,7]; or in sum, due to lower wing loading [8]. Smaller general aviation aircraft and helicop-ters also tend to fly more at lower altitudes within the Atmospheric Boundary Layer (ABL) which is dominated by high turbulence intensities from ground protruding structures [7,9]. This has led to reported accidents directly relating to turbulence [10][11][12][13].…”

Section: Background and Objectivesmentioning

confidence: 99%

Gusts Encountered by Flying Vehicles in Proximity to Buildings

Abdel‐Rohman

Marino

Watkins

et al. 2022

Drones

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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.

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“…Researchers are studying the urban environment [40,41] and acoustic signature of small-scale rotors employed in the UA. The relationship between SPL and distance, the altitude, and the orientation of the UA are studied with respect to the receptor [42].…”

Section: Sound Emission Modelling-the "Noise At Source" Problemmentioning

confidence: 99%

Sound Propagation Modelling for Manned and Unmanned Aircraft Noise Assessment and Mitigation: A Review

et al. 2021

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This paper addresses one of the recognized barriers to the unrestricted adoption of Unmanned Aircraft (UA) in mainstream urban use—noise—and reviews existing approaches for estimating and mitigating this problem. The aircraft noise problem is discussed upfront in general terms by introducing the sound emission, propagation, and psychoacoustic effects. The propagation of sound in the atmosphere, which is the focus of this paper, is then analysed in detail to isolate the environmental and operational factors that predominantly influence the perceived noise on the ground, especially looking at large-scale low-altitude UA operations, such as in the envisioned Urban Air Mobility (UAM) concepts. The physics of sound propagation are presented, considering all attenuation effects and the anomalies due to Doppler and atmospheric effects, such as wind, thermal inversion, and turbulence. The analysis allows to highlight the limitations of current mainstream aircraft noise modelling and certification approaches and, in particular, their inadequacy in addressing the noise of UA and, more generally, UAM vehicles. This finding is important considering that, although reducing noise at the source has remained a priority for manufacturers to enable the scaling up of UAM and drone delivery operations in the near future, the impact of poorly considered propagation and psychoacoustic effects on the actual perceived noise on the ground is equally important for the same objective. For instance, optimizing the flight paths as a function of local weather conditions can significantly contribute to minimizing the impact of noise on communities, thus paving the way for the introduction of full-scale UAM operations. A more reliable and accurate modelling of noise ground signatures for both manned and unmanned low-flying aircraft will aid in identifying the real-time data stream requirements from distributed sensors on the ground. New developments in surrogate sound propagation models, more pervasive real-time sensor data, and suitable computing resources are expected to both yield more reliable and effective estimates of noise reaching the ground listeners and support a dynamic planning of flight paths.

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Flight-Relevant Gusts: Computation-Derived Guidelines for Micro Air Vehicle Ground Test Unsteady Aerodynamics

Cited by 17 publications

References 24 publications

Avian whiffling-inspired gaps provide an alternative method for roll control

Avian whiffling-inspired gaps provide an alternative method for roll control

Gusts Encountered by Flying Vehicles in Proximity to Buildings

Sound Propagation Modelling for Manned and Unmanned Aircraft Noise Assessment and Mitigation: A Review

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