Evolution of flow structures in twin-rotors wakes in drones by time-resolved PIV

Nargi, Ranieri Emanuele; Gregorio, F. De; Candeloro, Paolo; Ceglia, Giuseppe; Pagliaroli, Tiziano

doi:10.1088/1742-6596/1977/1/012008

Cited by 4 publications

(5 citation statements)

References 7 publications

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“…This indicates that the rotor wake at V d /V h = 1.08 lies in a flow state referred to as incipient VRS, wherein the flow switches intermittently between the VRS and tubular topologies. This result agrees with those presented in earlier studies (Newman et al 2003;Green et al 2005), which observed the intermittent transition of the rotor wake into a VRS form at the onset of VRS. Figures 6(e, f ) show the representative instantaneous fields of the rotor wakes at V d /V h = 1.30 and 1.52, respectively.…”

Section: Resultssupporting

confidence: 93%

“…Lee et al (2021) suggested a modelling equation to predict the tip vortex trajectory considering the effect of rotor-rotor interaction during hovering for multi-rotor configurations. Wake characteristics that are complicated by the rotor-rotor interaction significantly affect the aerodynamic performances of multi-rotor systems, including the mean thrust generation (Intaratep et al 2016;Yoon et al 2016;Zhou et al 2017;Lee & Lee 2020;Veismann & Gharib 2020;Lee et al 2021), force fluctuations (Zhou et al 2017;Lee & Lee 2020) and noise (Intaratep et al 2016;Zhou et al 2017;Lee & Lee 2020;Nargi et al 2021).…”

Section: Introductionmentioning

confidence: 99%

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Effects of rotor–rotor interaction on the wake characteristics of twin rotors in axial descent

2022

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In this study, the effects of rotor–rotor interaction on wake characteristics were investigated experimentally for a twin-rotor configuration in axial descent. The wake velocities were measured at descent rates (descent speed/induced velocity at the rotor disk during hover) from 0.87 to 1.52, and the rotor–rotor interaction strength was controlled by adjusting the distance between the rotor tips. As the descent rate increased, the wake of the isolated rotor gradually entered the vortex ring state (VRS), where the flow established an extensive recirculation zone. Correlation analysis was performed to distinguish the rotor wake between tubular and VRS topologies. The flow states for the isolated rotor were classified into pre-VRS, incipient VRS, and fully developed VRS, depending on the probability of vortex ring formation. The results reveal that the effects of rotor–rotor interaction on the wake characteristics of twin rotors differ depending on the descent rate, distance between rotor tips, and wake region. In the outer region, the flow state of the rotor wake remains consistent with that of the isolated rotor, irrespective of the distance between rotor tips. Conversely, the strong rotor–rotor interaction changes the flow state in the inner region by disrupting the vortex ring structure, intensifying the wake asymmetry about the rotational axis. The thrust measurements show that under the VRS, as the two rotors get closer, the thrust coefficient increases until vortex ring disruption occurs, and then decreases after the vortex ring is disrupted.

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Section: Resultssupporting

confidence: 93%

Section: Introductionmentioning

confidence: 99%

Effects of rotor–rotor interaction on the wake characteristics of twin rotors in axial descent

2022

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“…For the code validations, the results obtained by each partner were shared among the action group. Three data bases of test data were available from DLR [2][3], CIRA/CUSANO [4] [5] and Polimi [6]. In addition, the first common test campaigns involving PIV measurement were carried out by CIRA/DLR [7], using the DLR small rotor configurations [2] [3].…”

Section: Introductionmentioning

confidence: 99%

Acoustic and Aerodynamic Evaluation of Dlr Small-Scale Rotor Configurations Within Garteur AG26

Yin,

Gregorio,

Rossignol

et al. 2024

Preprint

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This paper presents the activities performed in the GARTEUR Action Group HC/AG-26 to study the acoustic and aerodynamic characteristics of small rotor configurations, including the influence of the rotor-rotor interactions. This paper will focus on comparisons between numerical activities and wind tunnel results on a small rotor provided by DLR. The wind tunnel models included a Rotor/Rotor/Pylon in isolated, tandem and coaxial configuration. The wind tunnel experiments for acoustics were performed in DLR’s Acoustic Wind Tunnel Braunschweig (AWB) and PIV test were performed in CIRA within a joint CIRA/DLR test program. For simulations, the numerical approaches from each partner are applied. The aerodynamic simulations necessary for the aeroacoustic predictions are conducted with various fidelity numerical methods, varying from lifting line to CFD. The acoustic values on the microphone positions are evaluated using Ffowcs Williams-Hawking (FW-H) formulation by all partners. The acoustic and aerodynamic predictions are compared to test data, including performance, PIV and acoustic directivity.

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“…1 Aerodynamics and aero-acoustics of propellers and rotors have been under investigation for decades. 3,4 Examples of previous aero-acoustic research have focused on a single isolated rotor (without a wing underneath), 1,[5][6][7][8][9] two or multiple tandem rotors (without a wing underneath), [10][11][12][13] and scaled tiltrotor models (with a wing underneath): V-22 14 and XV-15. [15][16][17] The aforementioned aeroacoustic studies on the V-22 (Figure 1 31 (c) Germandrones Songbird, 32 and (d) Wingcopter.…”

Section: Introductionmentioning

confidence: 99%

Acoustic measurements in single-rotor/wing interaction at low disk loading and Reynolds number

Chen,

Hua,

Maier

et al. 2023

International Journal of Aeroacoustics

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The tiltrotor design is favored for urban air mobility (UAM) prototypes due to the combination of vertical takeoff and landing (VTOL) capability and efficient forward flight. With rising UAM air traffic at low altitudes, noise from these aircraft is a crucial design factor. Most tiltrotor noise research focuses on high disk loading and Reynolds number setups, leaving smaller aircraft configurations less explored. This study investigates aero-acoustic trends from rotor-wing interaction at low disk loading ([Formula: see text]100 N/m2) and Reynolds number (Re < 100,000). While prior literature suggests lowering disk loading and reducing rotor wake interference can mitigate rotor noise, such ideas lack empirical validation. The setup involves an anechoic chamber housing a two-blade rotor, along with flat and NACA 0012 airfoil wings. Microphones and a rotation stage capture acoustic data for analysis. Factors like flow recirculation, isolated rotor noise, rotor height, rotation direction/rate, and wing curvature are assessed for impact on noise signature. It is found that the deflected rotor wake in rotor-wing interaction significantly increases low-frequency broadband noise and overall sound pressure level (OASPL), compared to an isolated rotor. Dominant tonal noise diminishes based on the strength of the deflected rotor wake. These findings offer insights into reducing noise from rotor wake impingement on the wing.

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Evolution of flow structures in twin-rotors wakes in drones by time-resolved PIV

Cited by 4 publications

References 7 publications

Effects of rotor–rotor interaction on the wake characteristics of twin rotors in axial descent

Effects of rotor–rotor interaction on the wake characteristics of twin rotors in axial descent

Acoustic and Aerodynamic Evaluation of Dlr Small-Scale Rotor Configurations Within Garteur AG26

Acoustic measurements in single-rotor/wing interaction at low disk loading and Reynolds number

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