Aeroacoustic Study of small scale Rotors for mini Drone Propulsion: Serrated Trailing Edge Effect.

Pagliaroli, Tiziano; Camussi, Roberto; Candeloro, Paolo; Giannini, Oliviero; Bella, Gino

doi:10.2514/6.2018-3449

Cited by 8 publications

(12 citation statements)

References 15 publications

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“…In that steady loading framework, the latter is found to be relatively small without significantly contributing to the overall noise while the former is found to be dominant independently of the observer's location. In addition, one source of broadband noise is considered, as being initially thought as predominant 10 : the noise due to the scattering of the boundary layer disturbances at the trailing edge. This noise component has been modelled by Roger and Moreau.…”

Section: Acoustic Modellingmentioning

confidence: 99%

“…Such models based on analytical developments seem promising 6 although generally found in small axial fans research. A pure aerodynamic optimization of micro-air vehicle (MAV) propellers has been published by Gur and Rosen 7 but an optimization based on both aerodynamic and acoustic characteristics has rarely been addressed although some noise reduction techniques were applied yielding promising conclusions such as an unequal blade spacing to reduce the tonal noise, 8 boundary layer trips 9 or trailing-edge serrations 10 to remove the broadband noise. In these earlier studies, the sound was considered as mainly tonal with a broadband contribution due to the scattering of boundary layer perturbations by the blade trailing edge.…”

Section: Introductionmentioning

confidence: 99%

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Towards silent micro-air vehicles: optimization of a low Reynolds number rotor in hover

Serré

Gourdain

Jardin

et al. 2019

International Journal of Aeroacoustics

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The demand in micro-air vehicles is increasing as well as their potential missions. Either for discretion in military operations or noise pollution in civilian use, noise reduction of micro-air vehicles is a goal to achieve. Aeroacoustic research has long been focusing on full scale rotorcrafts. At micro-air vehicle scales however, the hierarchization of the numerous sources of noise is not straightforward, as a consequence of the relatively low Reynolds number that ranges typically from 5000 to 100,000 and low Mach number of approximately 0.1. This knowledge, however, is crucial for aeroacoustic optimization and blade noise reduction in drones. This contribution briefly describes a low-cost, numerical methodology to achieve noise reduction by optimization of micro-air vehicle rotor blade geometry. Acoustic power measurements show a reduction of 8 dB(A). The innovative rotor blade geometry allowing this noise reduction is then analysed in detail, both experimentally and numerically with large eddy simulation using lattice Boltzmann method. Turbulence interaction noise is shown to be a major source of noise in this configuration of low Reynolds number rotor in hover, as a result of small scale turbulence and high frequency unsteady aeroadynamics impinging the blades at the leading edge.

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Section: Acoustic Modellingmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Towards silent micro-air vehicles: optimization of a low Reynolds number rotor in hover

Serré

Gourdain

Jardin

et al. 2019

International Journal of Aeroacoustics

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“…On the contrary, an increase in the overall noise may occur due mainly to aerodynamic effects. Serration depth effect is also analysed by Pagliaroli et al [17], in particular, as regards broad-band noise component and the directivity of the noise source in the near-field. A notable reduction in the noise generated was obtained in the low frequency region and damping in the tails of the probability density function (PDF) was observed.…”

Section: Serrated Trailing Edgementioning

confidence: 99%

“…The university of Southampton is working mainly on leading edge modification to reduce interaction noise [14,15], whereas main research topic of ISAE-SUPAERO is the design of a quiet propeller by means of an optimization process [16]. Instead, Niccolò Cusano University is focusing on trailing edge modification to reduce the broad-band noise component generated by propellers [17]. Furthermore, numbers of research groups working on this topic have increased.…”

Section: Introductionmentioning

confidence: 99%

Small-Scale Rotor Aeroacoustics for Drone Propulsion: A Review of Noise Sources and Control Strategies

Candeloro¹,

Pagliaroli²,

Ragni³

et al. 2019

Preprint

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In the last decade, the drone market has grown rapidly for both civil and military purposes. Due to their versatility, drones demand is constantly increasing, with several industrial players joining the venture to transfer urban mobility to the air. This has exacerbated the problem of noise pollution, mainly due to the relatively lower altitude of these vehicles and to the proximity of their routes to extremely densely populated areas. In particular, both the aerodynamic and aeroacoustic optimization of the propulsive system and of its interaction with the airframe are key aspects of the design of aerial vehicles for the success or the failure of their mission. The industrial challenge involves finding the best performance in terms of loading, efficiency and weight, and, at the same time, the most silent configuration. For this reason, research has focused on an initial localization of the noise sources and, on further analysis, of the noise generation mechanism, focusing particularly on directivity and scattering. The aim of the present study is to review the noise source mechanisms and the state-of-the-art technologies available in literature for its suppression, focusing especially on the fluid-dynamic aspects of low Reynolds numbers of the propulsive system and on the interaction of the propulsive-system flow with the airframe.

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“…Generally, the propeller aerodynamic noise is divided into narrow-and broadband components [18,[23][24][25]:…”

Section: Introductionmentioning

confidence: 99%

An Experimental Study of the Aeroacoustic Properties of a Propeller in Energy Harvesting Configuration

Candeloro

Martellini

Nederlof

et al. 2022

Fluids

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The aim of the present manuscript is to investigate the noise footprint of an isolated propeller in different flight configurations for the propulsion of a hybrid-electric aircraft. Experimental tests were performed at the Low-Turbulence Tunnel located at Delft University of Technology with a powered propeller model and flush-mounted microphones in the tunnel floor. The propeller was investigated at different advance ratios in order to study the noise impact in propulsive and energy harvesting configurations. For brevity, this work only reports the results at the conditions of maximum efficiency in both propulsive and energy harvesting regimes, for a fixed blade pitch setting. Comparing these two configurations, a frequency-domain analysis reveals a significant modification in the nature of the noise source. In the propulsive configuration, most of the energy is related to the tonal noise component, as expected for an isolated propeller; however, in energy harvesting configuration, the broadband noise component increases significantly compared to the propulsive mode. A more detailed analysis requires separation of the two noise components and, for this purpose, an innovative decomposition strategy based on proper orthogonal decomposition (POD) has been defined. This novel technique shows promising results; both in the time and in the Fourier domains the two reconstructed components perfectly describe the original signal and no phase delays or other mathematical artifices are introduced. In this sense, it can represent a very powerful tool to identify noise sources and, at the same time, to define a proper control strategy aimed at noise mitigation.

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Aeroacoustic Study of small scale Rotors for mini Drone Propulsion: Serrated Trailing Edge Effect.

Cited by 8 publications

References 15 publications

Towards silent micro-air vehicles: optimization of a low Reynolds number rotor in hover

Towards silent micro-air vehicles: optimization of a low Reynolds number rotor in hover

Small-Scale Rotor Aeroacoustics for Drone Propulsion: A Review of Noise Sources and Control Strategies

An Experimental Study of the Aeroacoustic Properties of a Propeller in Energy Harvesting Configuration

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