Special Issue "Advances in Vibroacoustics and Aeroacustics of Marine, Aerospace and Automotive Systems"

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

Deadline for manuscript submissions: 10 November 2021.

Special Issue Editors

Dr. Luigi Federico
E-Mail Website
Guest Editor
Head of Environmental Impact of Air Transport System Dept., Italian Aerospace Research Center (CIRA), Via Maiorise, 81043 Capua (CE), Italy
Interests: vibroacoustics; aeroacoustics; aerospace systems; Air Traffic Management (ATM)
Special Issues, Collections and Topics in MDPI journals
Dr. Venanzio Giannella
E-Mail Website
Guest Editor
Department of Industrial Engineering, University of Salerno, 132 - 84084 Fisciano, Italy
Interests: fatigue; fracture; FEM; BEM; vibroacoustics; advanced materials
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

The purpose of this Special Issue is to highlight the latest enhancements in the abatement of noise and vibrations of marine, aerospace and automotive systems. The reduction of acoustic emissions and the improvement of cabin interior comfort are on the path of all major industries of the transport system, having a direct impact on customer satisfaction and, consequently, on the commercial success of new products. The main topics covered in this Special Issue deal with computational, instrumentation and data analysis of noise and vibrations of ships, fixed-wing aircrafts, rotating wing aircrafts, space launchers and automotive vehicles. This Special Issue covers, but is not limited to, aerodynamically generated noise, engine noise, sound absorption, cabin acoustic treatments, duct acoustics, active noise control, porous materials and vibroacoustic properties of structures and materials. This Special Issue provides an opportunity for scientists and engineers to publish their studies of current interest, both in the computational and experimental fields of research, and also articles to introduce new approaches and methodologies.

Dr. Roberto Citarella
Dr. Luigi Federico
Dr. Venanzio Giannella
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. Applied Sciences is an international peer-reviewed open access semimonthly 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 2000 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

  • Vibroacoustics
  • Aeroacoustics
  • Acoustics, noise, vibration, aeronautics, automotive, marine
  • BEM, FEM, SEA
  • Ray Tracing
  • Passive Noise Control
  • Active Noise Control

Published Papers (8 papers)

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Research

Article
Experimental/Numerical Acoustic Assessment of Aircraft Seat Headrests Based on Electrospun Mats
Appl. Sci. 2021, 11(14), 6400; https://doi.org/10.3390/app11146400 - 11 Jul 2021
Viewed by 497
Abstract
The work proposes a methodology for the assessment of the performances of Passive Noise Control (PNC) for passenger aircraft headrests with the aim of enhancing acoustic comfort. Two PNC improvements of headrests were designed to reduce the Sound Pressure Level (SPL) at the [...] Read more.
The work proposes a methodology for the assessment of the performances of Passive Noise Control (PNC) for passenger aircraft headrests with the aim of enhancing acoustic comfort. Two PNC improvements of headrests were designed to reduce the Sound Pressure Level (SPL) at the passengers’ ears in an aircraft cabin during flight; the first was based on the optimization of the headrest shape, whereas the second consisted of partially or fully covering the headrest surface with a new highly sound-absorbing nanofibrous textile. An experimental validation campaign was conducted in a semi-anechoic chamber. A dummy headrest was assembled in different configurations of shape and materials to assess the acoustic performances associated to each set up. In parallel, simulations based on the Boundary Element Method (BEM) were performed for each configuration and an acceptable correlation between experimental and numerical results was obtained. Based on these findings, general guidelines were proposed for the acoustical design of advanced headrests. Full article
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Article
FEM Modelling Approaches of Bolt Connections for the Dynamic Analyses of an Automotive Engine
Appl. Sci. 2021, 11(10), 4343; https://doi.org/10.3390/app11104343 - 11 May 2021
Cited by 2 | Viewed by 379
Abstract
Three different finite element method (FEM) modelling approaches of bolt connections of a four-stroke, four-cylinder petrol engine are presented, and the related results compared in terms of preprocessing time and accuracy. A full 3D modelling of the bolt connections was preliminarily validated through [...] Read more.
Three different finite element method (FEM) modelling approaches of bolt connections of a four-stroke, four-cylinder petrol engine are presented, and the related results compared in terms of preprocessing time and accuracy. A full 3D modelling of the bolt connections was preliminarily validated through a comparison with experimental test data available for the whole engine. Two further modelling approaches, a 1D approach and a contact-based (0D) approach, were benchmarked considering their influence on the accuracy for the dynamic analysis of an engine. Each of the three approaches presented pros and cons, even if the 1D modelling could be envisaged as the recommended one in most of cases. Full article
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Article
3D Acoustic Mapping in Automotive Wind Tunnel: Algorithm and Problem Analysis on Simulated Data
Appl. Sci. 2021, 11(7), 3241; https://doi.org/10.3390/app11073241 - 04 Apr 2021
Viewed by 523
Abstract
Localization and quantification of noise sources are important to fulfill customer and regulation requirements in a such competitive sector like automotive manufacturing. Wind tunnel testing and acoustic mapping techniques based on microphone arrays can provide accurate information on these aspects. However, it is [...] Read more.
Localization and quantification of noise sources are important to fulfill customer and regulation requirements in a such competitive sector like automotive manufacturing. Wind tunnel testing and acoustic mapping techniques based on microphone arrays can provide accurate information on these aspects. However, it is not straightforward to get source positions and strengths in these testing conditions. In fact, the car is a 3D object that radiates noise from different parts simultaneously, involving different noise generation mechanisms such as tire noise and aerodynamic noise. Commonly, acoustic maps are produced on a 3D surface that envelopes the objects. However, this practice produces misleading and/or incomplete results, as acoustic sources can be generated outside the surface. When the hypothesis of sources on the model surface is removed, additional issues arise. In this paper, we propose exploiting an inverse method tailored to a volumetric approach. The aim of this paper is to investigate the issues to face when the method is applied to automotive wind tunnel testing. Two different kinds of problem must be considered: On the one hand, the results of inverse methods are strongly influenced by the problem definition, while, on the other hand, experimental conditions must be taken into account to get accurate results. These aspects have been studied making use of simulated experiments. Such a controlled simulation environment, by contrast to a purely experimental case, enables accurate assessment of both the localization and quantification performance of the proposed method. Finally, a set of scores is defined to evaluate the resulting maps with objective metrics. Full article
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Article
A Method for Rainfall Detection and Rainfall Intensity Level Retrieval from X-Band Marine Radar Images
Appl. Sci. 2021, 11(4), 1565; https://doi.org/10.3390/app11041565 - 09 Feb 2021
Cited by 1 | Viewed by 426
Abstract
Currently, it is a hot research topic to retrieve the wave parameters by using X-band marine radar. However, the rainfall noise usually exists in the collected marine radar images, which seriously interferes with the extraction of the wave parameters. To reduce the influence [...] Read more.
Currently, it is a hot research topic to retrieve the wave parameters by using X-band marine radar. However, the rainfall noise usually exists in the collected marine radar images, which seriously interferes with the extraction of the wave parameters. To reduce the influence of rainfall noise, the zero-pixel percentage (ZPP) method is widely used to detect rainfall in radar images, but the detection accuracy is limited, and the selection of the threshold needs to be further studied. Based on the ZPP method, the ratio of zero intensity to echo (RZE) method for rainfall detection is proposed in this paper. The detection threshold is determined by statistical analysis of a large amount of radar data. Additionally, it is proposed for the first time to retrieve the rainfall intensity level from X-band marine radar images. In addition, the concept of the occlusion area is proposed. The proposed area and the wave area are used as the rainfall detection area of the radar image, respectively, for experimental research. The data obtained from the Pingtan experimental base in Fujian Province are used to verify the effectiveness of the proposed method. The experimental results show that the detection accuracy of the proposed method is 11.7% higher than that of the ZPP method, and the accuracy of rainfall intensity level retrieval is 84%. Full article
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Article
Vibroacoustic Assessment of an Innovative Composite Material for the Roof of a Coupe Car
Appl. Sci. 2021, 11(3), 1128; https://doi.org/10.3390/app11031128 - 26 Jan 2021
Viewed by 529
Abstract
The objective of this paper is the vibroacoustic evaluation of an innovative material for a sports car roof, aiming at replacing fiberglass composite materials. Such evaluation was carried out using numerical and experimental analysis techniques, with cross-comparison between the corresponding results. The innovative [...] Read more.
The objective of this paper is the vibroacoustic evaluation of an innovative material for a sports car roof, aiming at replacing fiberglass composite materials. Such evaluation was carried out using numerical and experimental analysis techniques, with cross-comparison between the corresponding results. The innovative material under analysis is a composite material, with a thermoplastic polypropylene matrix and reinforcement made of cellulose fibers. In order to validate the virtual dynamic modeling of the new material, the inertance on different points of some sheets made of the material under analysis was evaluated by an in-house made experimental activity, performed in the CRF (Fiat Research Center) test room, and cross-compared with corresponding results from a numerical analysis performed with the MSC Nastran software. Then, a realistic model of the car roof of the Alfa Romeo 4C car, made with the new material, was implemented and analyzed from the vibroacoustic point of view. The mere switch to the new material, with no changes in the geometry/structure of the car roof, did not allow preserving the original values of static rigidity, dynamic rigidity, and configuration of modal shapes. For this reason, a geometric/structural optimization of the component was performed. Once the new geometry/structure was defined, a vibroacoustic analysis was carried out, checking for a possible coupling between the fluid cavity modes and the structure car body modes. Finally, the vibroacoustic transfer functions to the driver’s ear node were assessed, considering two different excitation points on the structure. The excellent damping capacity of the proposed material led to an improvement in the vibroacoustic transfer functions and to a reduction in the weight of the pavilion. Full article
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Article
Aeroaocustic Numerical Analysis of the Vehicle Model
Appl. Sci. 2020, 10(24), 9066; https://doi.org/10.3390/app10249066 - 18 Dec 2020
Viewed by 576
Abstract
Understanding local phenomena connected with airflow around road vehicles allows to reduce the negative impact of transportation on the environment. This paper presents using numerical tools for Computational Fluid Dynamics (CFD) and Computational AeroAcoustic (CAA) calculation. As a model for simulation, simplified car [...] Read more.
Understanding local phenomena connected with airflow around road vehicles allows to reduce the negative impact of transportation on the environment. This paper presents using numerical tools for Computational Fluid Dynamics (CFD) and Computational AeroAcoustic (CAA) calculation. As a model for simulation, simplified car geometry is used, which is known in the research community as an Ahmed body. The study is divided into two main parts: a validation process and a CAA analysis using the Ffowcs Williams–Hawkings (FW-H) analogy. Research is performed using kω Shear Stress Transport (SST) and the Large Eddy Simulation (LES) turbulence model. To compare results with other authors’ studies, three different comparison criteria are introduced: a drag coefficient for different velocities, characteristic flow structure, and velocity profiles. The CAA analysis is presented using colormaps and Fast Fourier Transformation (FFT). The methods used in this work allow visualizing the acoustic field around reference geometry and determining the frequency range for which the A-weighted sound pressure level is the highest. Full article
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Article
Acoustic Improvements of Aircraft Headrests Based on Electrospun Mats Evaluated Through Boundary Element Method
Appl. Sci. 2020, 10(16), 5712; https://doi.org/10.3390/app10165712 - 18 Aug 2020
Cited by 2 | Viewed by 580
Abstract
This work illustrates the development of passive noise control (PNC) improvements of aircraft headrests to enhance the acoustic comfort for passengers. Two PNC improvements were studied with the aim of reducing the noise perceived by passengers during flight. Two headrest configurations, with and [...] Read more.
This work illustrates the development of passive noise control (PNC) improvements of aircraft headrests to enhance the acoustic comfort for passengers. Two PNC improvements were studied with the aim of reducing the noise perceived by passengers during flight. Two headrest configurations, with and without the lateral caps, and two different materials, a traditional foam and an innovative Silica/Polyvinylpyrrolidone (PVP) woven non-woven mat, were considered, and compared in terms of sound pressure level (SPL) perceived by passengers. Boundary element method (BEM) models were built up to evaluate the acoustic performances of different headrest configurations, varying in terms of shape and textile. A spherical distribution of monopole sources surrounding the headrests was considered as acoustic load, in such a way as to recreate a diffuse acoustic field simulating the cabin noise perceived by passengers during cruise conditions. The impact of the two PNC improvements was analyzed to envisage some general guidelines useful to design advanced headrests from the acoustic viewpoint. Full article
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Article
Numerical Investigation of Unsteady Flow and Aerodynamic Noise Characteristics of an Automotive Axial Cooling Fan
Appl. Sci. 2020, 10(16), 5432; https://doi.org/10.3390/app10165432 - 06 Aug 2020
Cited by 2 | Viewed by 792
Abstract
Low-speed axial cooling fans are frequently used to manage engine temperature by ensuring that adequate quantities of air pass through heat exchangers, even at low vehicle speeds or in the idle condition. This study aims to provide a better understanding of the unsteady [...] Read more.
Low-speed axial cooling fans are frequently used to manage engine temperature by ensuring that adequate quantities of air pass through heat exchangers, even at low vehicle speeds or in the idle condition. This study aims to provide a better understanding of the unsteady flow behavior around an automotive axial cooling fan with seven blades and its impact on the aerodynamic noise generation. Large Eddy Simulation (LES) near the near-field region and the Ffowcs-Williams and Hawkinbygs (FW-H) method were performed to analyze the flow characteristics around the fan and predict the aerodynamic noise emitted from the fan under a constant rotational speed of 2100 rpm. The simulation results for the velocity distributions and aerodynamic noise were compared with the experimental data measured by single hot-wire probe and in a dead-sound room. The results showed a comparatively good agreement upstream and downstream from the fan and at two different receivers of 0.5 m and 1.0 m. When the fan was rotating, a strong tonal noise numerically existed near the leading edge of the blades at the tip and amounted to 110 dB sound pressure level (SPL) caused by the increasing angles of attack with the increasing radial velocity near the ring, which caused the entire air foil to emit a low-frequency noise. Furthermore, the different SPL decay characteristics of approximately 5 dB in the near-field region and 6 dB in the far-field region were observed each time the distance from the fan doubles. The findings of this research can provide important insights into the design of axial fans with low noise and high performance. Full article
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