Broadband noise prediction when turbulence simulation is available—Derivation of Formulation 2B and its statistical analysis

Farassat, F.; Casper, Jay

doi:10.1016/j.jsv.2011.07.044

Cited by 11 publications

(2 citation statements)

References 17 publications

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“…While Farassat's Formulation 1A is commonly used for deterministic noise prediction, 133 it has not been widely used for the prediction of nondeterministic noise. However, Farassat developed Formulations 1B 134 and 2B 135 specifically for broadband noise computations. These formulations may be useful if detailed time domain loading data are available, for instance from high fidelity computational tools such as those described in the next section.…”

Section: Ingestion Noisementioning

confidence: 99%

Challenges and opportunities for low noise electric aircraft

Greenwood

Brentner

Rau

et al. 2022

International Journal of Aeroacoustics

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A new class of electric aircraft is being developed to transport people and goods as a part of the urban and regional transportation infrastructure. To gain public acceptance of these operations, these aircraft need to be much quieter than conventional airplanes and helicopters. This article seeks to review and summarize the aeroacoustic research relevant to this new category of aircraft. First, a brief review of the history of electric aircraft is provided, with an emphasis on how these aircraft differ from conventional aircraft. Next, the physics of rotor noise generation are reviewed, and the noise sources most likely to be of concern for electric aircraft are highlighted. These are divided into deterministic and nondeterministic sources of noise. Deterministic noise is expected to be dominated by the unsteady loading noise caused by the aerodynamic interactions between components. Nondeterministic noise will be generated by the interaction of the rotor or propeller blades with turbulence from ingested wakes, the atmosphere, and self-generated in the boundary layer. The literature for these noise sources is reviewed with a focus on applicability to electric aircraft. Challenges faced by the aeroacoustician in understanding the noise generation of electric aircraft are then identified, as well as the new opportunities for the prediction and reduction of electric aircraft noise that may be enabled by advances in computational aeroacoustics, flight simulation, and autonomy.

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Section: Ingestion Noisementioning

confidence: 99%

Challenges and opportunities for low noise electric aircraft

Greenwood

Brentner

Rau

et al. 2022

International Journal of Aeroacoustics

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show abstract

“…18-24¯ 2 There are several solutions to the FW-H equation proposed by Farassat, including the most frequently used Formulation 1A. 8 During his time in the Aeroacoustics Branch at the NASA Langley Research Center, Farassat 25 proposed that any general solution to the FW-H equation satisfy the following requirements which are taken verbatim from Ref. 25: 1.…”

Section: Compact Monopole Formulationsmentioning

confidence: 99%

Compact Assumption Applied to Monopole Term of Farassat’s Formulations

Lopes

2017

Journal of Aircraft

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Farassat's formulations provide an acoustic prediction at an observer location provided a source surface, including motion and flow conditions. This paper presents compact forms for the monopole term of several of Farassat's formulations. When the physical surface is elongated, such as the case of a high aspect ratio rotorcraft blade, compact forms can be derived which are shown to be a function of the blade cross sectional area by reducing the computation from a surface integral to a line integral. The compact forms of all formulations are applied to two example cases: a short span wing with constant airfoil cross section moving at three forward flight Mach numbers and a rotor at two advance ratios. Acoustic pressure time histories and power spectral densities of monopole noise predicted from the compact forms of all the formulations at several observer positions are shown to compare very closely to the predictions from their non-compact counterparts. A study on the influence of rotorcraft blade shape on the high frequency portion of the power spectral density shows that there is a direct correlation between the aspect ratio of the airfoil and the error incurred by using the compact form. Finally, a prediction of pressure gradient from the non-compact and compact forms of the thickness term of Formulation G1A shows that using the compact forms results in a 99.6% improvement in computation time, which will be critical when noise is incorporated into a design environment.

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Influence Due to the Blade Number on the Stator Tonal and Broadband Noise

Wei

Jin

et al. 2021

Acoust Aust

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Broadband noise prediction when turbulence simulation is available—Derivation of Formulation 2B and its statistical analysis

Cited by 11 publications

References 17 publications

Challenges and opportunities for low noise electric aircraft

Challenges and opportunities for low noise electric aircraft

Compact Assumption Applied to Monopole Term of Farassat’s Formulations

Influence Due to the Blade Number on the Stator Tonal and Broadband Noise

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