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Airframe Noise and Airframe/Propulsion Integration

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A special issue of Applied Sciences (ISSN 2076-3417). This special issue belongs to the section "Acoustics and Vibrations".

Deadline for manuscript submissions: closed (31 December 2020) | Viewed by 27727

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Special Issue Editor

Prof. Dr. Vladimir V. Golubev

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Guest Editor

Department of Aerospace Engineering, Embry-Riddle Aeronautical University, Daytona Beach, FL 32114-3900, USA
Interests: computational fluid dynamics; computational aeroacoustics; flow control
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

As the traditional areas of aeroacoustic research such as jet, fan, and turbomachinery noise have achieved remarkable success in reducing the aircraft propulsion noise signature, airframe noise and its control have become an important focus of studies. Among those, high-fidelity analysis and the control of acoustic radiation from high-lift devices and landing gear dominate the research efforts. There is also an increasing interest to explore and employ unconventional airframe-propulsion integration configurations for further aircraft noise reduction, achieved, e.g., through airframe shielding of engine noise radiation. This Special Issue serves to give a review and prospective for the state-of-the-art in analysis and control approaches related to airframe and propulsion/airframe integration acoustics. Your contributions toward this issue is greatly appreciated. If you have any questions regarding the Special Issue, please feel free to contact the Guest Editor.

Prof. Vladimir V. Golubev
Guest Editor

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Keywords

Propulsion airframe aeroacoustic integration
Advanced low-noise aircraft configurations
Airframe shielding
Sonic boom
High-lift devices
Landing gear
Trailing edge noise
UAV noise
High-fidelity analysis
Active and passive noise control

Published Papers (7 papers)

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Research

Jump to: Review

29 pages, 14949 KiB

Open AccessArticle

Numerical Investigation of Tonal Trailing-Edge Noise Radiated by Low Reynolds Number Airfoils

by Lap Nguyen, Vladimir Golubev, Reda Mankbadi, Gyuzel Yakhina and Michel Roger

Appl. Sci. 2021, 11(5), 2257; https://0-doi-org.brum.beds.ac.uk/10.3390/app11052257 - 04 Mar 2021

Cited by 10 | Viewed by 1832

Abstract

A high-fidelity computational analysis carefully validated against concurrently obtained experimental results is employed to examine self-noise radiation of airfoils at transitional flow regimes, with a focus on elucidating the connection between the unsteady behavior of the laminar separation bubble (LSB) and the acoustic feedback-loop (AFL) resonant interactions observed in the airfoil boundary layers. The employed parametric study examines AFL sensitivity to the changes in the upstream flow conditions and the airfoil loading. Implicit Large-Eddy Simulations are performed for a NACA-0012 airfoil in selected transitional-flow regimes for which experimental measurements recorded characteristic multiple-tone acoustic spectra with a dual ladder-type frequency structure. The switch between the tone-producing and no-tone-producing regimes is traced to the LSB size and position as a function of the flow Reynolds number and the airfoil angle of attack, and further substantiated by the linear stability analysis. The results indicate a strong multi-tonal airfoil noise radiation associated with the AFL and attributed to the switch from the slowly-growing Tollmien–Schlichting to the fast-growing Kelvin–Helmholtz instabilities occurring in thin LSB regions when those are localized near the trailing-edge (TE) on either side of the airfoil. Such a process eventually results in the nonlinearly saturated flapping vortical modes (“rollers”) that scatter into acoustic waves at the TE. Full article

(This article belongs to the Special Issue Airframe Noise and Airframe/Propulsion Integration)

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11 pages, 3373 KiB

Open AccessArticle

Single and Multivariate Statistics of Jet-Induced Pressure Fluctuations over an Infinite Plate

by Stefano Meloni, Roberto Camussi, Alessandro Di Marco and Matteo Mancinelli

Appl. Sci. 2020, 10(13), 4605; https://0-doi-org.brum.beds.ac.uk/10.3390/app10134605 - 02 Jul 2020

Cited by 2 | Viewed by 1483

Abstract

Motivated by the problem of the installation effects of modern turbofan engines, we experimentally investigated the interaction between a compressible subsonic jet and a tangential flat plate. Measurements of wall pressure fluctuations were performed in a semi-anechoic environment addressing the effect of several governing parameters, such as the stream-wise and span-wise location, the jet Mach number and the radial distance of the plate surface from the jet axis. The statistical properties of the wall pressure signals were analyzed in terms of both power spectra and cross-correlations, with the latter providing the estimation of the phase speed. The analysis is also carried out in the time-frequency domain through the application of the wavelet transform to further characterize the dynamics of the wall pressure signatures. Full article

(This article belongs to the Special Issue Airframe Noise and Airframe/Propulsion Integration)

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18 pages, 8697 KiB

Open AccessArticle

Numerical Characterisation of the Aeroacoustic Signature of Propeller Arrays for Distributed Electric Propulsion

by Giovanni Bernardini, Francesco Centracchio, Massimo Gennaretti, Umberto Iemma, Claudio Pasquali, Caterina Poggi, Monica Rossetti and Jacopo Serafini

Appl. Sci. 2020, 10(8), 2643; https://0-doi-org.brum.beds.ac.uk/10.3390/app10082643 - 11 Apr 2020

Cited by 26 | Viewed by 3796

Abstract

This paper presents an investigation of the aerodynamic and aeroacoustic interaction of propellers for distributed electric propulsion applications. The rationale underlying the research is related to the key role that aeroacoustics plays in the establishment of the future commercial aviation scenario. The sustainable development of airborne transportation system is currently constrained by community noise, which limits the operations of existing airports and prevents the building of new ones. In addition, the substantial saturation of the existing noise abatement technologies inhibits the further development of the existing fleet, and imposes the adoption of disruptive configurations in terms of airframe layout and propulsion technology. Simulation-based data may help in clarifying many aspects related to the acoustic impact of such innovative concepts. Blended-wing-body equipped with distributed electric propulsion is one of the most promising, due to the beneficial effect of the substantial shielding induced by its geometry. Nevertheless, the novelty of the layout requires a thorough investigation of specific aspect for which no previous experience is available. Herein, the interaction between propellers is analysed for a fixed propeller geometry, as a function of their mutual distance and compared to the acoustic pattern of the isolated one. The aerodynamic results have been obtained using a boundary integral formulation for unsteady, incompressible, potential flows which accounts for the interaction between free wakes and propellers. For the aeroacoustic analyses, the Farassat 1A boundary integral formulation for the solution of the Ffowcs Williams and Hawkings equation has been used. These results provide an insight into the minimum distance between propellers to avoid aerodynamic/aeroacoustic interaction effects, which is an important starting point for the development of distributed propulsion systems. Full article

(This article belongs to the Special Issue Airframe Noise and Airframe/Propulsion Integration)

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29 pages, 15379 KiB

Open AccessArticle

Jet Noise in Airframe Integration and Shielding

by Saman Salehian and Reda Mankbadi

Appl. Sci. 2020, 10(2), 511; https://0-doi-org.brum.beds.ac.uk/10.3390/app10020511 - 10 Jan 2020

Cited by 16 | Viewed by 4881

Abstract

This paper reviews and presents new results on the effect of airframe integration and shielding on jet noise. Available experimental data on integration effects are analyzed. The available options for the computation of jet noise are discussed, and a practical numerical approach for the present topic is recommended. Here, it is demonstrated how a hybrid large eddy simulation—unsteady Reynolds-averaged Navier-Stokes approach can be implemented to simulate the effect of shielding on radiated jet noise. This approach provides results consistent with the experiment and suggests a framework for studying more complex geometries involving airframe integration effects. Full article

(This article belongs to the Special Issue Airframe Noise and Airframe/Propulsion Integration)

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18 pages, 7138 KiB

Open AccessArticle

Predicting Far-Field Noise Generated by a Landing Gear Using Multiple Two-Dimensional Simulations

by Sultan Alqash, Sharvari Dhote and Kamran Behdinan

Appl. Sci. 2019, 9(21), 4485; https://0-doi-org.brum.beds.ac.uk/10.3390/app9214485 - 23 Oct 2019

Cited by 4 | Viewed by 3264

Abstract

In this paper, a new approach is proposed to predict the far-field noise of a landing gear (LG) based on near-field flow data obtained from multiple two-dimensional (2D) simulations. The LG consists of many bluff bodies with various shapes and sizes. The analysis begins with dividing the LG structure into multiple 2D cross-sections (C-Ss) representing different configurations. The C-Ss locations are selected based on the number of components, sizes, and geometric complexities. The 2D Computational Fluid Dynamics (CFD) analysis for each C-S is carried out first to obtain the acoustic source data. The Ffowcs Williams and Hawkings acoustic analogy (FW-H) is then used to predict the far-field noise. To compensate for the third dimension, a source correlation length (SCL) is assumed based on a perfectly correlated flow. The overall noise of the LG is calculated as the incoherent sum of the predicted noise from all C-Ss. Flow over a circular cylinder is then studied to examine the effect of the 2D CFD results on the predicted noise. The results are in good agreement with reported experimental and numerical data. However, the Strouhal number (St) is over-predicted. The proposed approach provides a reasonable estimation of the LG far-field noise at a low computational cost. Thus, it has the potential to be used as a quick tool to predict the far-field noise from an LG during the design stage. Full article

(This article belongs to the Special Issue Airframe Noise and Airframe/Propulsion Integration)

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Review

Jump to: Research

25 pages, 13006 KiB

Open AccessEditor’s ChoiceReview

Recent Advances in Acoustics of Transitional Airfoils with Feedback-Loop Interactions: A Review

by Vladimir Golubev

Appl. Sci. 2021, 11(3), 1057; https://0-doi-org.brum.beds.ac.uk/10.3390/app11031057 - 25 Jan 2021

Cited by 12 | Viewed by 3077

Abstract

We discuss herein recent experimental and numerical studies examining resonant flow-acoustic feedback–loop interactions in transitional airfoils (i.e., possessing a notable area of laminar-to-turbulent boundary-layer transition) characteristic of low-to-medium Reynolds number flow regimes. Such interactions are commonly attributed to the viscous dynamics of the convected boundary-layer structures scattering into acoustic waves at the trailing edge which propagate upstream and re-excite the convected vortical structures. While it has been long suspected that the acoustic feedback mechanism is responsible for the highly pronounced, often multi-tonal response, the exact reason of how the boundary-layer instability structures could reach a sufficient degree of amplification to sustain the feedback-loop process and exhibit specific tonal signature remained unclear. This review thus pays particular attention to the critical role of the separation bubble in the feedback process and emphasizes the complementary roles of the experimental and numerical works in elucidating an intricate connection between the airfoil radiated tonal acoustic signature and the properties of the separation zones as determined by airfoil geometry and flow regimes. Full article

(This article belongs to the Special Issue Airframe Noise and Airframe/Propulsion Integration)

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43 pages, 2781 KiB

Open AccessReview

Bio-Inspired Aerodynamic Noise Control: A Bibliographic Review

by Yong Wang, Kun Zhao, Xiang-Yu Lu, Yu-Bao Song and Gareth J. Bennett

Appl. Sci. 2019, 9(11), 2224; https://0-doi-org.brum.beds.ac.uk/10.3390/app9112224 - 30 May 2019

Cited by 49 | Viewed by 8810

Abstract

It is well-known that many species of owl have the unique ability to fly silently, which can be attributed to their distinctive and special feather adaptations. Inspired by the owls, researchers attempted to reduce the aerodynamic noise of aircraft and other structures by learning their noise reduction features from different viewpoints and then using the gained knowledge to develop a number of innovative noise reduction solutions. Although fruitful results have been achieved in the bio-inspired aerodynamic noise control, as far as the authors know, comparatively little work has been done to summarize the main findings and progresses in this area. In this bibliographic survey, we systematically review the progresses and trends of the bio-inspired aerodynamic noise control, including the macroscopic and microscopic morphological characteristics of the owl wing feathers, the noise measurements on both flying birds in the field and prepared wings in the wind tunnel, as well as theoretical, numerical and experimental studies that explored the feasibility, parameter influence, aerodynamic effects and underlying mechanisms of the four main bio-inspired noise reduction techniques, i.e., leading edge serrations, trailing edge serrations, fringe-type trailing edge extensions and porous material inspired noise reduction. Finally, we also give some suggestions for future work. Full article

(This article belongs to the Special Issue Airframe Noise and Airframe/Propulsion Integration)

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