Compact Assumption Applied to Monopole Term of Farassat’s Formulations

Lopes, Leonard V.

doi:10.2514/1.c034048

Cited by 23 publications

(9 citation statements)

References 24 publications

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“…Moreover, computational savings of up to 99.5% have been reported with only slight deviations compared to the corresponding non-compact discrete-frequency acoustic pressure computations (Ref. 30,31).…”

Section: Rotor Aeroacoustics Modelmentioning

confidence: 92%

Impact of Tip-Vortex Modeling Uncertainty on Helicopter Rotor Blade–Vortex Interaction Noise Prediction

Vouros¹,

Goulos²,

Scullion³

et al. 2021

j am helicopter soc

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Free-wake models are routinely used in aeroacoustic analysis of helicopter rotors; however, their semiempiricism is accompanied with uncertainty related to the modeling of physical wake parameters. In some cases, analysts have to resort to empirical adaption of these parameters based on previous experimental evidence. This paper investigates the impact of inherent uncertainty in wake aerodynamic modeling on the robustness of helicopter rotor aeroacoustic analysis. A free-wake aeroelastic rotor model is employed to predict high-resolution unsteady airloads, including blade–vortex interactions. A rotor aeroacoustics model, based on integral solutions of the Ffowcs Williams–Hawkings equation, is utilized to calculate aerodynamic noise in the time domain. The individual analytical models are incorporated into an uncertainty analysis numerical procedure, implemented through nonintrusive Polynomial Chaos expansion. The potential sources of uncertainty in wake tip-vortex core growth modeling are identified and their impact on noise predictions is systematically quantified. When experimental data to adjust the tip-vortex core model are not available the uncertainty in acoustic pressure and noise impact at observers dominated by blade–vortex interaction noise can reach up to 25% and 3.50 dB, respectively. A set of generalized uncertainty maps is derived, for use as modeling guidelines for aeroacoustic analysis in the absence of the robust evidence necessary for calibration of semiempirical vortex core models.

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Section: Rotor Aeroacoustics Modelmentioning

confidence: 92%

Impact of Tip-Vortex Modeling Uncertainty on Helicopter Rotor Blade–Vortex Interaction Noise Prediction

Vouros¹,

Goulos²,

Scullion³

et al. 2021

j am helicopter soc

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show abstract

“…The compact acoustic formulations adopted in this study are compatible with the lifting-linetype aerodynamic input provided by the free-wake airloads model. Moreover, computational savings of up to 99.5% have been reported with only slight deviations from the corresponding non-compact deterministic acoustic pressure computations [30], [32]. This enables the incorporation of on-the-fly and physics-based rotor source noise prediction into the simulation of complete rotorcraft operations.…”

Section: Near-field Noise Prediction Modelmentioning

confidence: 92%

“…Additionally, v is the source surface velocity vector, u is the fluid velocity vector and n is the unit outward normal vector to the source surface. [33] and followed by Lopes [32], the compact expressions of thickness and loading acoustic pressure can be formed as follows:…”

Section: Near-field Noise Prediction Modelmentioning

confidence: 99%

Integrated methodology for the prediction of helicopter rotor noise at mission level

Vouros

Goulos

Pachidis

2019

Aerospace Science and Technology

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This paper presents an integrated approach for the aeroacoustic assessment of fourdimensional rotorcraft operations. A comprehensive rotorcraft code is utilized to model aircraft flight dynamics across complete missions. A free-wake aero-elastic rotor model is employed to predict high-resolution unsteady airloads, including blade-vortex interactions, at each mission element. A rotor aeroacoustics code is developed to calculate source noise and far-field ground acoustic impact. Time-domain acoustic formulations are used to evaluate near-field noise generation across designated acoustic spherical surfaces surrounding the helicopter main rotor. A numerical procedure is developed for the derivation of acoustic spheres on-the-fly, coupled with trajectory-adaptive ground observer grids. The individual analytical models are incorporated into a mission analysis numerical procedure. The applicability of the integrated method on "real-world" rotorcraft operations is demonstrated for two generic, four-dimensional missions, without the need of pre-stored noise data. The proposed approach provides insight into helicopter noise prediction at mission level, elaborating on the coupling of aeroelastic rotor response with rotorcraft flight dynamics and aeroacoustics.

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“…In order to predict the acoustic metrics, a tool that predicts thickness, loading, and broadband noise, acoustic propagation and observer noise is necessary. The Aircraft NOise Prediction Program 2 (ANOPP2, [16][17][18]) and AeroAcoustic ROtor Noise (AARON) tools provide the acoustic calculations in the toolchain. AARON is the user code to perform rotorcraft calculations with ANOPP2.…”

Section: Aaron/anopp2mentioning

confidence: 99%

NASA concept vehicles and the engineering of advanced air mobility aircraft

Johnson

Silva

2021

Aeronaut. j.

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NASA is conducting investigations in Advanced Air Mobility (AAM) aircraft and operations. AAM missions are characterised by ranges below 300 nm, including rural and urban operations, passenger carrying as well as cargo delivery. Urban Air Mobility (UAM) is a subset of AAM and is the segment that is projected to have the most economic benefit and be the most difficult to develop. The NASA Revolutionary Vertical Lift Technology project is developing UAM VTOL aircraft designs that can be used to focus and guide research activities in support of aircraft development for emerging aviation markets. These NASA concept vehicles encompass relevant UAM features and technologies, including propulsion architectures, highly efficient yet quiet rotors, and aircraft aerodynamic performance and interactions. The configurations adopted are generic, intentionally different in appearance and design detail from prominent industry arrangements. Already these UAM concept aircraft have been used in numerous engineering investigations, including work on meeting safety requirements, achieving good handling qualities, and reducing noise below helicopter certification levels. Focusing on the concept vehicles, observations are made regarding the engineering of Advanced Air Mobility aircraft.

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Compact Assumption Applied to Monopole Term of Farassat’s Formulations

Cited by 23 publications

References 24 publications

Impact of Tip-Vortex Modeling Uncertainty on Helicopter Rotor Blade–Vortex Interaction Noise Prediction

Impact of Tip-Vortex Modeling Uncertainty on Helicopter Rotor Blade–Vortex Interaction Noise Prediction

Integrated methodology for the prediction of helicopter rotor noise at mission level

NASA concept vehicles and the engineering of advanced air mobility aircraft

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