Early Onset Prediction for Rotors in Vortex Ring State

McQuaid, Joel A.; Kolaei, Amir; Bramesfeld, Goetz; Walsh, Paul

doi:10.1061/(asce)as.1943-5525.0001194

Cited by 6 publications

(3 citation statements)

References 10 publications

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“…The obtained flow fields of this study can be compared with computational flow field results of closely arranged twin-rotor (Takii et al, 2020) and multirotor (McQuaid et al, 2020;Veismann et al, 2021) configurations in axial descent found in the literature. In the interest of brevity, this comparison will be qualitative in nature and readers are encouraged to consult the provided literature for their own, in-depth analysis.…”

Section: Flow Field Analysismentioning

confidence: 94%

“…To date, only few computational efforts have been dedicated to the investigation of non-overlapping, twin-rotors (Takii, Yamakawa, & Asao, 2020) or multirotors (McQuaid, Kolaei, Bramesfeld, & Walsh, 2020;Veismann et al, 2021) in descent, which similarly indicated severe aerodynamic losses and strong vehicle oscillations while providing a closer look into the flow field properties of these rotor systems in the VRS. It is worth noting that all aforementioned studies exclusively considered counter-rotating rotor arrangements, as this is typically used in practice for torque balancing.…”

Section: E7-3mentioning

confidence: 99%

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Effects of rotor separation on the axial descent performance of dual-rotor configurations

Veismann

Dougherty

Gharib

2023

Flow

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Rotorcraft can encounter highly unsteady flow when descending at a steep angle, leading to a flow condition called vortex ring state, which is associated with strong oscillatory airloads and substantial losses in mean rotor thrust. This study examines the aerodynamic coupling between closely arranged rotors in vertical flight and assesses the extent to which rotor–rotor interactions affect the rotor performance in this flight stage. Wind tunnel experiments were performed on a small-scale, dual-rotor set-up with adjustable rotor spacing, and the effect of rotor separation on thrust generation was quantified. Pairs of 4 in., 5 in. and 6 in. rotors ( $3.0 \times 10^4< Re<8.1 \times 10^4$ ) were investigated, with load cell measurements showing significant thrust losses and concomitantly increased thrust oscillations as descent rate increased. Peak losses and fluctuations were consistently recorded at descent rates of 1.2–1.3 times the hover induced velocity for all rotor sizes and separations. While tests showed that the mean aerodynamic performance of dual-rotor systems is generally similar to that of single rotors, appreciable changes to the descent characteristics could be observed at low rotor separations. Particle image velocimetry flow visualization suggests considerable changes to the flow field as rotor separation decreases, where individual vortex ring systems merge into a single vortex ring structure.

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Section: Flow Field Analysismentioning

confidence: 94%

Section: E7-3mentioning

confidence: 99%

Effects of rotor separation on the axial descent performance of dual-rotor configurations

Veismann

Dougherty

Gharib

2023

Flow

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“…It considers a models of the coaxial and conventional four-bladed rotors of the Unmanned Aerial Vehicle (UAV). McQuaid et al [20] have also investigated the VRS modes using URANS method.…”

Section: Introductionmentioning

confidence: 99%

Comparative Study of 3-Bladed and Sсissors Tail Rotors Aerodynamics in Axial Flow

Makeev

Ignatkin

Shomov

et al. 2022

IREASE

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The paper is focused on the numerical study of the aerodynamic characteristics of 3bladed and scissors tail rotors used on Mi-8/17 series helicopters. The hovering and axial flow modes, including the Vortex Ring State (VRS) area are considered. The free wake model developed by authors is used in the research. The study has been performed for two approaches: with a fixed blade pitch angle and with a fixed time-average thrust value. The dependences of the rotor thrust and torque coefficients vs. axial flow velocity and vs. number of revolutions of a rotor have been obtained. The vortex wake shapes and flow images via streamlines have been analyzed. The comparative analysis of the results has been performed. Scissors rotor demonstrates better aerodynamic characteristics in comparison with 3-bladed rotor. Among them: increased hovering efficiency, lower level of thrust and torque pulsations in the VRS modes, smaller power consumption while constant thrust. The authors came to the conclusion about the greater efficiency of the aerodynamic design of scissors tail rotor compared to 3-bladed rotor both in hover and in the VRS modes area.

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Flow Field Analysis in Vortex Ring State Using Small Diameter Rotor by Descent Simulation

Mori,

Takii,

Yamakawa

et al. 2024

Lecture Notes in Computer Science

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Early Onset Prediction for Rotors in Vortex Ring State

Cited by 6 publications

References 10 publications

Effects of rotor separation on the axial descent performance of dual-rotor configurations

Effects of rotor separation on the axial descent performance of dual-rotor configurations

Comparative Study of 3-Bladed and Sсissors Tail Rotors Aerodynamics in Axial Flow

Flow Field Analysis in Vortex Ring State Using Small Diameter Rotor by Descent Simulation

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