Vertical Lift: Rotary- and Flapping-Wing Flight

A special issue of Aerospace (ISSN 2226-4310). This special issue belongs to the section "Aeronautics".

Deadline for manuscript submissions: 29 November 2024 | Viewed by 2899

Special Issue Editors


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Guest Editor
Alfred Gessow Rotorcraft Center, Department of Aerospace Engineering, University of Maryland, College Park, MD 20742, USA
Interests: rotary- and flapping-wing vehicles; modeling, simulation, and order reduction; flight dynamics and control; aeromechanics; rotorcraft handling qualities; system identification; time-periodic systems; human-machine interaction; virtual, augmented, and extended reality (VR/AR/XR)
Department of Mechanical Engineering, Pennsylvania State University, State College, PA 16802, USA
Interests: biomechanics and mechanobiology; mechanical sciences; sensors & controls

E-Mail Website
Guest Editor
Centre for Aviation (ZAV), Zurich University of Applied Sciences (ZHAW), 8400 Wintherthur, Switzerland
Interests: rotorcraft; flight mechanics; flight dynamics; flight control systems

Special Issue Information

Dear Colleagues,

Hovering is a fascinating ability in both engineering and biology, allowing rotary-wing vehicles and flapping-wing vehicles or insects (in contrast to fixed-wing vehicles) to remain stationary in the air relative to the ground. This shared capability places both rotary- and flapping-wing vehicles within the overarching category of vertical lift. This mode of flight presents significant challenges in terms of modeling and analysis due to its complexity. Challenges emanate from the multi-body, nonlinear, high-order, and time-varying dynamics inherent in these vehicles’ motion. In this type of locomotion, the time-varying wing/blade dynamics interact with the aggregate body dynamics and unsteady flow dynamics intricately and synergistically. Because the dynamics of hovering vehicles are typically unstable, high order, and with significant cross-coupling between motion axes, flight control design is often essential. Flight control systems are not only necessary for stabilizing the dynamics and imposing desired response characteristics but also, in the case of rotorcraft, for alleviating the workload of the pilot. Owing to these challenges, the study of vertical lift vehicles encompasses a wide range of multidisciplinary research areas. These include aerodynamics, flight dynamics, stability and control, structures, structural dynamics, aeroelasticity, propulsion, acoustics, autonomy, biology, and biomechanics. Therefore, this Special Issue is dedicated to showcasing the latest advancements in vertical lift and welcomes contributions in all the aforementioned areas, as they pertain to rotary- and flapping-wing vehicles.

Dr. Umberto Saetti
Dr. Bo Cheng
Dr. Pierluigi Capone
Guest Editors

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Keywords

  • rotorcraft
  • flapping-wing flight
  • aerodynamics
  • fluid dynamics
  • stability and control
  • structures
  • structural dynamics
  • aeroelasticity
  • propulsion
  • acoustics
  • autonomy
  • biology
  • biomechanics

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Published Papers (3 papers)

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Research

20 pages, 1380 KiB  
Article
Identification of High-Order Linear Time-Invariant Models from Periodic Nonlinear System Responses
by Mahmoud A. Hayajnh, Umberto Saetti and J. V. R. Prasad
Aerospace 2024, 11(11), 875; https://doi.org/10.3390/aerospace11110875 - 24 Oct 2024
Viewed by 366
Abstract
This paper presents a novel step in the extension of subspace identification toward the direct identification of harmonic decomposition linear time-invariant models from nonlinear time-periodic system responses. The proposed methodology is demonstrated through examples involving the nonlinear time-periodic dynamics of a flapping-wing micro [...] Read more.
This paper presents a novel step in the extension of subspace identification toward the direct identification of harmonic decomposition linear time-invariant models from nonlinear time-periodic system responses. The proposed methodology is demonstrated through examples involving the nonlinear time-periodic dynamics of a flapping-wing micro aerial vehicle. These examples focus on the identification of the vertical dynamics from various types of input–output data, including linear time-invariant, linear time-periodic, and nonlinear time-periodic input–output data. A harmonic analyzer is used to decompose the linear time-periodic and nonlinear time-periodic responses into harmonic components and introduce spurious dynamics into the identification, which make the identified model order selection challenging. A similar effect is introduced by measurement noise. The use of model order reduction and model-matching methods in the identification process is studied to recover the harmonic decomposition structure of the known system. The identified models are validated in the frequency and time domains. Full article
(This article belongs to the Special Issue Vertical Lift: Rotary- and Flapping-Wing Flight)
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24 pages, 10621 KiB  
Article
Gaze Movements of Helicopter Pilots during Real and Simulated Take-Off and Landing Maneuvers
by Daniel H. Greiwe and Maik Friedrich
Aerospace 2024, 11(6), 429; https://doi.org/10.3390/aerospace11060429 - 24 May 2024
Viewed by 838
Abstract
Most accidents and serious incidents of commercial air transport helicopters occur during standard flight phases, whereby a main cause is pilots’ situational awareness. Enabling pilots to better assess their situational awareness can make an important contribution in reducing the risk of fatal accidents. [...] Read more.
Most accidents and serious incidents of commercial air transport helicopters occur during standard flight phases, whereby a main cause is pilots’ situational awareness. Enabling pilots to better assess their situational awareness can make an important contribution in reducing the risk of fatal accidents. One approach is to examine a pilot’s gaze behavior with the help of eye tracking. This paper reports the results of a case study with eye tracking measurements during real flight and simulator studies of a standard mission profile. The general gaze behavior is characterized by a dominant, external view, and the airspeed and altitude indicator as the most important flight instruments. A real-world applicability of gaze data obtained in the simulator could be shown. Full article
(This article belongs to the Special Issue Vertical Lift: Rotary- and Flapping-Wing Flight)
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24 pages, 7316 KiB  
Article
Influence of Rotor Inflow, Tip Loss, and Aerodynamics Modeling on the Maximum Thrust Computation in Hover
by Berend G. van der Wall
Aerospace 2024, 11(5), 357; https://doi.org/10.3390/aerospace11050357 - 29 Apr 2024
Viewed by 1084
Abstract
Comprehensive rotorcraft simulation codes are the workhorses for designing and simulating helicopters and their rotors under steady and unsteady operating conditions. These codes are also used to predict helicopters’ limits as they approach rotor stall conditions. This paper focuses on the prediction of [...] Read more.
Comprehensive rotorcraft simulation codes are the workhorses for designing and simulating helicopters and their rotors under steady and unsteady operating conditions. These codes are also used to predict helicopters’ limits as they approach rotor stall conditions. This paper focuses on the prediction of maximum rotor thrust when hovering (due to stall limits) and the thrust and power characteristics when the collective control angle is further increased. The aerodynamic factors that may significantly affect the results are as follows: steady vs. unsteady aerodynamics, steady vs. dynamic stall, blade tip losses, curvature flow, yaw angle, inflow model, and blade-vortex interaction. The inflow model and tip losses are found to be the most important factors. For real-world applications vortex-based inflow models are considered the best choice, as they reflect the blade circulation distribution within the inflow distribution. Because the focus is on the impact of aerodynamic modeling on rotor stall, the blade design and its flexibility are intentionally not considered. Full article
(This article belongs to the Special Issue Vertical Lift: Rotary- and Flapping-Wing Flight)
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Planned Papers

The below list represents only planned manuscripts. Some of these manuscripts have not been received by the Editorial Office yet. Papers submitted to MDPI journals are subject to peer-review.

Title: Numerical modeling, trim, and linearization of a side-by-side helicopter in hover
Authors: Francesco Mazzeo; Marilena Pavel; Daniele Fattizzo; Emanuele Luigi de Angelis; Fabrizio Giulietti
Affiliation: Faculty of Aerospace Engineering, Delft University of Technology
Abstract: In the present paper, a flight dynamics model is adopted to represent the trim and stability characteristics of a side-by-side helicopter in hovering conditions. The paper develops a numerical representation of the rotorcraft behavior and proposes a set of guidelines for trimming and linearizing the highly-coupled rotor dynamics derived by the modeling approach. The trim algorithm presents two nested loops to compute a solution of the steady-state conditions averaged around one blade’s revolution. On the other hand, a 38-state-space linear representation of the helicopter and rotor dynamics is obtained to study the effects of flap, lead-lag, and inflow on the overall stability. The results are compared with an analytical framework, developed to validate the rotorcraft stability and compare different modeling approaches. The analysis showed that a non-uniform inflow modeling led to a coupled longitudinal inflow-phugoid mode which made the vehicle prone to dangerous instabilities. The flap and lead-lag dynamics introduce damping in the system and can be considered beneficial for rotor dynamics.

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