Search Results (21)

In aerospace, flow control techniques have improved the separation flow characteristics around airfoils by various means. In this paper, the delayed detached eddy simulation (DDES) technique is used to simulate the detailed flow field around the NACA0021 airfoil with two different flow control methods (Gurney flaps and leading- and trailing-edge flaps) applied at an angle of attack of 20°. The aerodynamic characteristics around the airfoil under these two flow control methods are investigated, and the results show that both flow control methods lead to a significant increase in the pressure on the suction surface of the airfoil, which contributes to an increase in lift. The aeroacoustic characteristics of the original airfoil, the Gurney flapped airfoil and the airfoil with leading-edge and trailing-edge flaps are then analyzed using a combination of DDES and FW-H acoustic analog equations. The results show that the total sound pressure level of the Gurney flap airfoil and the leading-edge and trailing-edge flap airfoil are improved in most azimuthal angles of the acoustic pointing distribution, among which the degree of improvement of the leading-edge and trailing-edge flap airfoil is greater than that of the Gurney flap airfoil near the trailing edge, and the total sound pressure level of the band leading- and trailing-edge flap airfoil decreases in the azimuthal angles near the leading edge. Compared with the original airfoil, the noise value is thus reduced by up to 4.13 dB. The results of pressure pulsation cloud map, sound pressure level cloud map on the airfoil surface and vortex cloud map distribution show that the two flow controls increase the pressure pulsation near the trailing edge, the range and peak value of sound emission on the airfoil surface increase, and the trailing vortex becomes more finely grained, which leads to an increase in noise. Full article

This work presents the design and implementation of an emergency sound detection and localization system, specifically for sirens and horns, aimed at enhancing road safety in automotive environments. The system integrates specialized hardware and advanced artificial intelligence algorithms to function effectively in complex acoustic conditions, such as urban traffic and environmental noise. It introduces an aerodynamic structure designed to mitigate wind noise and vibrations in microphones, ensuring high-quality audio capture. In terms of analysis through artificial intelligence, the system utilizes transformer-based architecture and convolutional neural networks (such as residual networks and U-NET) to detect, localize, clean, and analyze nearby sounds. Additionally, it operates in real-time through sliding windows, providing the driver with accurate visual information about the direction, proximity, and trajectory of the emergency sound. Experimental results demonstrate high accuracy in both controlled and real-world conditions, with a detection accuracy of 98.86% for simulated data and 97.5% for real-world measurements, and localization with an average error of 5.12° in simulations and 10.30° in real-world measurements. These results highlight the effectiveness of the proposed approach for integration into driver assistance systems and its potential to improve road safety. Full article

To enable wind energy to surpass fossil fuels, the power-to-cost ratio of wind turbines must be competitive. Increasing installation capacities and wind turbine sizes indicates a strong trend toward clean energy. However, larger rotor diameters, reaching up to 170 m, introduce stability and aeroelasticity concerns and aerodynamic phenomena that cause noise disturbances. These issues hinder performance enhancement and social acceptance of wind turbines. A critical aerodynamic challenge is flow separation on the blade’s suction side, leading to a loss of lift and increased drag, ultimately stalling the blade and reducing turbine performance. Various active and passive flow control techniques have been studied to address these issues, with passive techniques offering the advantage of no external energy requirement. High-lift devices, such as leading-edge slats, are promising in improving aerodynamic performance by controlling flow separation. This study explores the geometric parameters of slats and their effects on wind turbine blades’ aerodynamic and acoustic performance. Using an adequate turbulence model at Re = 10⁶ for angles of attack from 14° to 24°, 77 slat configurations were evaluated. Symmetric slats showed superior performance at high angles of attack, while slat chord length was inversely proportional to aerodynamic improvement. A hybrid method was employed to predict noise, revealing slat-induced modifications in eddy topology and increased low- and high-frequency noise. This study’s main contribution is correlating slat-induced aerodynamic improvements with their acoustic effects. The directivity reveals a 10–15 dB reduction induced by the slat at 1 kHz, while the slat induces higher noise at higher frequencies. Full article

In conventional gasoline automobiles, the engine powers the air conditioning system and engine noise can somewhat mask the noise and vibration of the air conditioning system. In pure electric vehicles, however, the absence of an engine makes the air conditioning system’s noise more noticeable, concentrated in a limited frequency range at constant speeds. As a result, aerodynamic noise from the air conditioning system is a primary noise source in electric vehicles. Pipeline silencers are the main method for reducing this noise. The current silencer design uses plane wave acoustic theory but when cavity modal resonance occurs, the transmission loss error is relatively high. This article addresses the issue of non-planar wave cavity resonance, studying the cavity modal of a muffler using the finite element method to reveal the transmission loss under cavity mode resonance. A dual cavity expansion structure of an impedance composite muffler is proposed, with sound-absorbing materials placed in the cavity to enhance acoustic performance. The analysis of the transmission loss characteristics of the impedance composite muffler provides a theoretical basis for noise control in pure electric vehicle air conditioning systems. Full article

Tautosyllabic segment sequences exhibit greater gestural overlap than heterosyllabic ones. In Spanish, it is presumed that word-final consonants followed by a word-initial vowel undergo resyllabification, and generative phonology assumes that canonical CV.CV# and derived CV.C#V onsets are structurally identical. However, recent studies have not found evidence of this structural similarity in the acoustics. The current goal is to investigate anticipatory and carryover vowel nasalization patterns in tautosyllabic, heterosyllabic, and resyllabified segment sequences in Spanish. Nine native speakers of Peninsular Spanish participated in a read-aloud task. Nasal airflow data were extracted using pressure transducers connected to a vented mask. Each participant produced forty target tokens with CV.CV# (control), CVN# (tautosyllabic), CV.NV# (heterosyllabic), and CV.N#V (resyllabification) structures. Forty timepoints were obtained from each vowel to observe airflow dynamics, resulting in a total of 25,200 datapoints analyzed. Regarding anticipatory vowel nasalization, the CVN# sequence shows an earlier onset of nasalization, while CV.NV# and CV.N#V sequences illustrate parallel patterns among them. Carryover vowel nasalization exhibited greater nasal spreading than anticipatory nasalization, and vowels in CV.NV# and CV.N#V structures showed symmetrical nasalization patterns. These results imply that syllable structure affects nasal gestural overlap and that aerodynamic characteristics of vowels are unaffected across word boundaries. Full article

(1) Background: Assessing phonatory disorders due to laryngeal biomechanical alterations requires aerodynamic analysis, assessing subglottic pressure, transglottic flow, and laryngeal resistance. This study explores whether the acoustic parameter, the relative fundamental frequency (RFF), can be studied using the current acoustic analysis protocol at the University of Navarra’s voice laboratory and its association with pathologies linked to laryngeal biomechanical alterations. (2) Methods: A retrospective cohort study included patients diagnosed with muscular tension dysphonia, organic lesions of the vocal fold, and vocal fold paralysis (VFP) at the Clínica Universidad de Navarra from 2019 to 2021. Each patient underwent endoscopic laryngeal exploration, followed by acoustic study, RFF calculation, and an aerodynamic study. Additionally, a control group was recruited. (3) Results: 79 patients and 22 controls were studied. Two-way ANOVA showed significant effects for groups and cycles in offset and onset cycles. Statistically significant differences were observed in cycle 1 onset among all groups and in cycles 1 and 2 between the control group and non-healthy groups. (4) Conclusions: RFF is a valuable indicator of phonatory biomechanics, distinguishing healthy and pathological voices and different disorders. RFF in onset cycles offers a cost-effective, accurate method for assessing biomechanical disorders without complex aerodynamic analyses. This study describes RFF values in VFP for the first time, revealing differences regardless of aerodynamic patterns. Full article

This study considers the practical issue of severe noise observed in a multi-stage sleeve control valve within an engineering project. Employing computational fluid dynamics (CFD) methodology, we initially performed numerical simulations to analyze the steady-state flow field within the control valve. Subsequently, we identified the underlying factors contributing to the noise issue within the valve. To assess the aerodynamic noise of the control valve, we applied the FW-H acoustic analogy theory and determined the intensity and distribution characteristics of the aerodynamic noise. Finally, we validated the numerical simulation results of the aerodynamic noise against theoretical calculations. Our findings indicate that the steam medium experiences high-speed flow due to disturbances caused by various components within the valve, resulting in significant turbulence intensity. This intense turbulence leads to pressure fluctuations in the steam, serving as the main catalyst for noise generation. The aerodynamic noise of the control valve exhibits a roughly symmetrical distribution along the pipe–valve system, with noticeable increases in noise levels upstream and downstream of the valve compared to other regions. The distribution cloud map obtained from the numerical simulations serves as a valuable reference for analyzing the locations where aerodynamic noise is generated. Comparing the numerical simulation results with the theoretical calculations at the noise monitoring points, we found that the noise error of the monitoring points was less than 5%, which proves the effectiveness of the numerical simulation method. These results provide essential data support for the acoustic detection of aerodynamic noise in control valves, carrying significant practical implications for engineering applications. Full article

Aerodynamic noise produced by the rotating blade is an important hindrance for the rapid development of modern wind turbines. Among the various noise sources, the airfoil trailing edge noise contributes a lot to the wind turbine noise. The control of wind turbine airfoil trailing edge self-noise by bio-inspired sinusoidal wavy leading edges is experimentally studied in a semi-anechoic chamber. The noise radiated by the baseline NACA 0012 airfoil and various wavy airfoils is measured using a planar microphone array consisting of fifty-two microphones. The noise source identifications are achieved by using the CLEAN-SC method. The effects of velocity and angle of attack on noise radiation of the baseline airfoil are analyzed in detail. The noise control law of the wavy amplitude and wavelength on airfoil trailing edge noise is explored. Based on the acoustic beamforming results, the noise control effects of the wavy leading edges are intuitively demonstrated. In general, the wavy leading edge with a larger amplitude and smaller wavelength has a better effect on the airfoil trailing edge noise reduction. The maximum sound pressure level reduction can be up to 33.9 dB. The results of this study are expected to provide important information for wind turbine aerodynamic noise control. Full article

To date, no established protocol exists for measuring functional voice changes in singers with subclinical singing-voice complaints. Hence, these may go undiagnosed until they progress into greater severity. This exploratory study sought to (1) determine which scale items in the self-perceptual Evaluation of Ability to Sing Easily (EASE) are associated with instrumental voice measures, and (2) construct as proof-of-concept an instrumental index related to singers’ perceptions of their vocal function and health status. Eighteen classical singers were acoustically recorded in a controlled environment singing an /a/ vowel using soft phonation. Aerodynamic data were collected during a softly sung /papapapapapapa/ task with the KayPENTAX Phonatory Aerodynamic System. Using multi and univariate linear regression techniques, CPPS, vibrato jitter, vibrato shimmer, and an efficiency ratio (SPL/P_Sub) were included in a significant model (p < 0.001) explaining 62.4% of variance in participants’ composite scores of three scale items related to vocal fatigue. The instrumental index showed a significant association (p = 0.001) with the EASE vocal fatigue subscale overall. Findings illustrate that an aeroacoustic instrumental index may be useful for monitoring functional changes in the singing voice as part of a multidimensional diagnostic approach to preventative and rehabilitative voice healthcare for professional singing-voice users. Full article

Due to the complexity of the working conditions and the diversity of application scenarios, the normal operation of a fan, whether volute tongue, volute shell surface, or blade, often encounters some unavoidable problems, such as flow separation, wear, vibration, etc.; the aerodynamic noise caused by these problems has a significant impact on the normal operation of the fan. However, despite the use of aerodynamic acoustics to design low-noise fans or the use of sound absorption, sound insulation, and sound dissipation as the main traditional noise control techniques, they are in a state of technical bottleneck. Thus, the search for more efficient methods of noise reduction is looking toward the field of bionics. For this purpose, this paper first analyzes the mechanism of fan noise in the volute tongue and blades, and then, this paper reviews the noise control mechanism and improvement research using the bionic structures in the volute tongue structure, the contact surface of the volute shell, and the leading and trailing edges of the blade in the centrifugal fan. Finally, the current challenges and prospects of bionic structures for aerodynamic noise control of centrifugal fans are discussed. Full article

Reducing rotor aerodynamic noise is an important challenge in helicopter design. Active flap control (AFC) on rotors is an effective noise reduction method. It changes the segment airfoil shape, aerodynamic load distribution, and the wake path of the rotor flow by adding trailing edge flaps (TEFs). Although AFC noise reduction control is easily simulated, the relevant experiments have not been widely conducted due to test technical problems and limited financial support. The acoustic characteristics of the AFC-equipped rotor, such as the placement of TEFs for noise reduction and whether multiple winglets can provide a better effect than single winglets, have not been verified in previous experiments. In this work, an AFC-equipped rotor with two TEFs was designed, and its acoustic properties were tested in the FL-17 acoustic wind tunnel with microphone arrays in the far field. The results showed that the noise reduction effect of AFC was closely related to the control frequency and phase. Increasing the control phase could move the reduction region toward the azimuth-decreasing region for far-field noise. The noise reduction in a single outboard TEF was better than that in a single inboard TEF, while the dual-TEF model performed better. In this experiment, the average noise reduction in the observation point at the lower front of the rotor could be more than 3 dB, and the maximum noise reduction could be 6.2 dB. Full article

The use of passive, active, or hybrid flow control techniques is often investigated to reduce the acoustic signature, wave drag, and aerodynamic heating associated with the supersonic flow regime. This research explores passive and hybrid flow control techniques to achieve an optimal reduction in wave drag and aerodynamic heating on a blunt body using an aerodisk. While passive techniques use one or two aerospikes, hybrid techniques employ opposing jets and aerospikes. Numerical analysis is performed using Reynolds-Averaged Navier–Stokes (RANS) equations to analyze the bodies’ flow field. The statistical technique, Design of Experiments (DOE), is combined with Response Surface Method (RSM) to find the optimal configuration for four cases by generating design space. Two cases were considered for the optimization: single aerospike with and without opposing jet and double aerospike with and without opposing jet. Variables used for the design of the aerodisks were spike length and diameter, while the response variables were wave drag and normalized heat flux. The current study has established an optimum relationship between spike length and aerospike diameter located in front of the main blunt body for both single and double aerospikes. The study’s results suggest that a double aerodisk configuration is more beneficial for reducing drag and heat flux at supersonic speed than a single aerodisk. By incorporating an opposing jet at a pressure ratio of 0.8 from the frontal aerodisk to the spiked blunt body, it can reduce drag and heat flux by 86% and 95%, respectively. Finally, numerical verification is performed for statistically optimized designs. Full article

Traditional voice evaluations, including imaging techniques, auditory-perceptual ratings, and acoustic and aerodynamic analyses, fail to assess the global handicap that a patient experiences as a result of a voice disorder. The Voice Handicap Index (VHI) is currently one of the most widely used and psychometrically robust instruments for measuring voice disability. The aim of the study is to translate and validate a Polish version of the VHI. The original English-language version of VHI-30 was translated into Polish. We enrolled 188 subjects—123 patients (91 women and 32 men) with voice disorders and 65 controls (53 women and 12 men) without voice disorders. Results obtained by the patients were significantly higher than those obtained by the controls on the Emotional subscale (U = 519.0; p < 0.001), Functional (U = 829.0; p < 0.001), Physical (U = 331.0; p < 0.001), and the global score (U = 390.0; p < 0.001). There were statistically significant negative correlations between maximum phonation time and global score (rho = −0.31; p < 0.01) as well as all three subscales. Shimmer and Smoothed Amplitude Perturbation Quotient were correlated positively with the global score (rho = 0.22; p < 0.05; rho = 0.25; p < 0.01, respectively) and with all three subscales. There were also statistically significant correlations between VHI scores and auditory perceptual evaluation. In the patient group, there was excellent internal consistency (α = 0.97) and strong test–retest reliability (intraclass correlation = 0.94). The cut-off value equal to 17 points was estimated. The Polish VHI showed excellent internal consistency, good test–retest reproducibility, and clinical validity. It is a useful tool for evaluating the voice disability perceived by a patient. Full article

The last decade has seen an exponential interest in conventional and unconventional energy issues. This trend has also extended to road transport issues and is driven by expectations to minimize fuel and/or energy consumption and negative environmental impact. In the global literature, much attention is focused on the work of autonomous transport, both passenger and trucks, and on the phenomena of platooning. The paper presents original aerodynamic and aeroacoustic tests of heterogeneous vehicle columns. In the work, models of a car, a van and a truck were built, followed by heterogeneous columns with different distances between the vehicles. Computational fluid dynamics (CFD) methods and two turbulence models, $k-\omega$ shear stress transport (SST) and large eddy simulation (LES), were used in this study. The study enabled the determination of drag coefficients and lift force. Application of the Ffowcs Williams–Hawkings (FW-H) analogy allowed for the determination of the distributions of sound pressure levels generated by moving vehicles and columns of vehicles. In order to verify the developed models, acoustic field measurements were made for the following passages: passenger car, van, and truck. Acoustic pressure level and A-weighted sound level (SPL) were measured in Krakow and in its vicinity. Research has shown that grouping vehicles into optimal columns and maintaining distances between vehicles using modern control systems can result in significant energy savings and reduce harmful emissions to the environment. Full article

Rotor plays a vital role in the dynamical system of an unmanned aerial vehicle (UAV). Prominent aerodynamic and acoustic performance are a long-term pursuit for the rotor. Inspired by excellent quiet flight characteristics of owls, this work adopted bionic edge design and rational material selection strategy to improve aerodynamic and acoustic performance of the rotor. A reference model of rotor prototype with streamlined edges was firstly generated by reverse engineering method. With inspiration from owl wings and feathers, bionic rotors with rational design on leading and trailing edges were obtained. Original and bionic rotors were fabricated with polyamide PA 12 and Resin 9400 by 3D printing technique. Aerodynamic and acoustic performance of the as-fabricated rotors were experimentally measured and analyzed in detail using a self-established test system. Comparative experimental results indicated that the aerodynamic and acoustic performance of the rotors was closely related to the bionic structures, material properties, and rotational speeds. At the same rotational speed, bionic rotor fabricated with Resin 9400 can produce a higher thrust than the prototype one and its power consumption was also reduced. The resulting noise of different bionic rotors and their directivities were comparatively investigated. The results verified the bionic edge design strategy can effectively control the turbulent flow field and smoothly decompose the airflow near the tailing edge, which resulting in enhancing the thrust and reducing the noise. This work could provide beneficial inspiration and strong clues for mechanical engineers and material scientists to design new abnormal rotors with promising aerodynamic and acoustic performance. Full article