Special Issue "Recent Advances in Aerodynamics and Aeroacoustics: Towards Greener Aviation"

A special issue of Fluids (ISSN 2311-5521).

Deadline for manuscript submissions: 31 March 2023 | Viewed by 6335

Special Issue Editors

Dr. Hasan Kamliya Jawahar
E-Mail Website
Guest Editor
Department of Aerospace Engineering, University of Bristol, Bristol BS8 1TH, UK
Interests: aerodynamics; aeroacoustics; high-lift device; hydrodynamics; propellers; turbulence; jets; experimentalfluid dynamics; flow-control; noise-control; wall-bounded flows; surface-treatments; computational fluid dynamics; large eddy simulation
Dr. Stefano Meloni
E-Mail Website
Guest Editor
Department of engineering, University of Roma Tre, 00154 Roma RM, Italy
Interests: aeroacoustics; fluid dynamics; wall pressure fluctuations; turbulence

Special Issue Information

Dear Colleagues,

Future civil air transport concepts such as supersonic aircrafts for long-range air routes and propeller-driven electric aircrafts for regional transports are continuously developing to reduce air pollution. However, their societal acceptance is key to their success, and it may be severely restricted in densely populated areas due to noise emissions.

A common denominator of these upcoming aircraft concepts is the formidable complexity of the highly unsteady aerodynamic and acoustic interactions with the adjacent propulsion systems and aircraft structures, affecting both the aerodynamic performance and noise emissions. The prediction of the aerodynamic performance and noise emission remains challenging, especially for the innovative non-conventional air transport concepts such as Blended Wing Body and Urban Air Mobility aircrafts.

This Special Issue of Fluids calls for high-quality papers in the fields of aerodynamics and aeroacoustics related to future aircraft technologies for greener aviation. We are very interested in receiving manuscripts from researchers from both academia and industry dealing with recent experimental, theoretical, and computational advances, as well as reviews showcasing the current state-of-the-art and all the perspectives related to a greener aviation.

Dr. Hasan Kamliya Jawahar
Dr. Stefano Meloni
Guest Editors

Manuscript Submission Information

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Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Fluids is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • aerodynamics
  • aeroacoustics
  • greener aviation
  • noise emissions
  • aircraft technologies

Published Papers (5 papers)

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Research

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Article
Aerodynamic Shape Optimization of a Symmetric Airfoil from Subsonic to Hypersonic Flight Regimes
Fluids 2022, 7(11), 353; https://doi.org/10.3390/fluids7110353 - 15 Nov 2022
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Abstract
Hypersonic flight has been the subject of numerous research studies during the last eight decades. This work aims to optimize the aerodynamic performance of a two-dimensional baseline airfoil (NACA0012) at distinct flight regimes from subsonic to hypersonic speeds. A mission profile has been [...] Read more.
Hypersonic flight has been the subject of numerous research studies during the last eight decades. This work aims to optimize the aerodynamic performance of a two-dimensional baseline airfoil (NACA0012) at distinct flight regimes from subsonic to hypersonic speeds. A mission profile has been defined, where four points representing the subsonic, transonic, supersonic, and hypersonic flow conditions have been selected. A framework has been implemented based on high-fidelity RANS computational fluid dynamics simulations. Gradient-based optimizations have been conducted with the objective of minimizing the drag. The optimization results show an overall improvement in aerodynamic performance, including a decrease in the drag coefficient of up to 79.2% when compared to the baseline airfoil. In the end, a morphing strategy has been laid out based on the optimal shapes produced by the optimization. Full article
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Article
An Experimental Study of the Aeroacoustic Properties of a Propeller in Energy Harvesting Configuration
Fluids 2022, 7(7), 217; https://doi.org/10.3390/fluids7070217 - 27 Jun 2022
Cited by 1 | Viewed by 1073
Abstract
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 [...] Read more.
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. Full article
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Article
Evaluation of Turbulent Jet Characteristic Scales Using Joint Statistical Moments and an Adaptive Time-Frequency Analysis
Fluids 2022, 7(4), 125; https://doi.org/10.3390/fluids7040125 - 25 Mar 2022
Cited by 1 | Viewed by 1384
Abstract
This paper presents an analysis of turbulence characteristic scales and eddy convection velocity of jet flows computed using joint statistical moments, digital filters, and a modified version of the empirical mode decomposition (EMD). The ongoing aim of this study is to develop semi-empirical [...] Read more.
This paper presents an analysis of turbulence characteristic scales and eddy convection velocity of jet flows computed using joint statistical moments, digital filters, and a modified version of the empirical mode decomposition (EMD). The ongoing aim of this study is to develop semi-empirical space-time cross-correlation models based on stationary statistics and jet physical lengths. Multivariate statistics are used to correlate jet properties to one-dimensional time series. The data available to this study were recorded from single-point and two-point hot-wire anemometry experiments carried out for a range of jet Mach numbers (0.2M0.8). Firstly, the jet eddy convection velocity, turbulence length, and time scales are computed using space-time cross-correlation functions. Isotropic flow and frozen turbulence hypothesis are then used to estimate the joint moments from single-point statistics in the fully developed turbulence region. An EMD-based decomposition method is presented and assessed in both the Gaussian and non-Gaussian signal regions. It is demonstrated that the artificially filtered signal reconstructs the physical properties of single and multi-point jet statistics. The relationship between central moments and joint moments presented here focuses on the region of high turbulence levels, which generates the vast majority of jet mixing noise produced by turbofan engines. Further analysis is required to extend this investigation to intermittent zones and other jet noise sources, such as jet-surface installation noise. Full article
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Article
A Wavelet-Based Time-Frequency Analysis on the Supersonic Jet Noise Features with Chevrons
Fluids 2022, 7(3), 108; https://doi.org/10.3390/fluids7030108 - 16 Mar 2022
Cited by 6 | Viewed by 1230
Abstract
A detailed investigation of the statistical properties of the near-field pressure fluctuations induced by an under-expanded jet, by varying the nozzle exit shapes has been presented. Experiments using different convergent Chevron nozzles were carried out in the anechoic chamber at the University of [...] Read more.
A detailed investigation of the statistical properties of the near-field pressure fluctuations induced by an under-expanded jet, by varying the nozzle exit shapes has been presented. Experiments using different convergent Chevron nozzles were carried out in the anechoic chamber at the University of Bristol to assess the importance of the Chevron shape on the near pressure field emitted by a single stream under-expanded jet. Measurements were carried out through an axial microphone array traversed radially to various positions for jet in an under-expanded condition at Mach number M = 1.3. The intermittent behavior is investigated considering the standard statistical indicators and a wavelet-based conditional approach, including the phase angle. The intermittent degree of various features related to different scales, such as Screech tones and broadband shock associate noise were estimated. A series of recently developed wavelet-based tools were assessed as a viable approach to investigate the noise emitted by under-expanded jets. Full article
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Review

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Review
Recent Advances in Passive Acoustic Localization Methods via Aircraft and Wake Vortex Aeroacoustics
Fluids 2022, 7(7), 218; https://doi.org/10.3390/fluids7070218 - 29 Jun 2022
Viewed by 1030
Abstract
Passive acoustic aircraft and wake localization methods rely on the noise emission from aircraft and their wakes for detection, tracking, and characterization. This paper takes a holistic approach to passive acoustic methods and first presents a systematic bibliographic review of aeroacoustic noise of [...] Read more.
Passive acoustic aircraft and wake localization methods rely on the noise emission from aircraft and their wakes for detection, tracking, and characterization. This paper takes a holistic approach to passive acoustic methods and first presents a systematic bibliographic review of aeroacoustic noise of aircraft and drones, followed by a summary of sound generation of wing tip vortices. The propagation of the sound through the atmosphere is then summarized. Passive acoustic localization techniques utilize an array of microphones along with the known character of the aeroacoustic noise source to determine the characteristics of the aircraft or its wake. This paper summarizes the current state of knowledge of acoustic localization with an emphasis on beamforming and machine learning techniques. This review brings together the fields of aeroacoustics and acoustic-based detection the advance the passive acoustic localization techniques in aerospace. Full article
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