Article
Engineering, Aerospace
Moritz Neubauer, Julia Genssler, Vincent Radmann, Fleming Kohlenberg, Michael Pohl, Kurt Boehme, Karsten Knobloch, Ennes Sarradj, Klaus Hoeschler, Niels Modler, Lars Enghardt
Summary: This paper presents a combined experimental and numerical investigation on a novel liner concept for enhanced low-frequency and broadband acoustic attenuation. Two different realizations, derived from traditional Helmholtz resonators (HR) and plate resonators (PR), are investigated. Experimental and analytical studies were conducted to study the effects of various geometric and material parameters on the acoustic dissipation and transmission loss.
Article
Acoustics
Leandro Rego, Francesco Avallone, Daniele Ragni, Damiano Casalino, Herve Denayer
Summary: A Helmholtz resonator with a curved cavity is studied for reducing jet-installation noise in a configuration comprised by a subsonic jet and a nearby flat plate. The results show that the resonators not only reduce the strength of the acoustic source, but also lower the sound pressure levels of the plate, achieving a noise reduction of approximately 7 dB at the resonance frequency of the single degree-of-freedom liner. The double degree-of-freedom resonator can further reduce the noise by about 3 dB at higher frequencies.
JOURNAL OF SOUND AND VIBRATION
(2022)
Article
Acoustics
Alexandru Crivoi, Liangfen Du, Zheng Fan
Summary: This study investigates the performance of a multilayer sound attenuating metamaterial with ventilation capacity based on arrays of wall-embedded Helmholtz resonators analytically, numerically, and experimentally. The sound attenuation in the audible range can be improved by using multiple layers with a unique peak resonance frequency assigned to each corresponding layer. However, trade-offs between thickness, ventilation capacity, operational frequency range, and integral sound attenuation exist. The simplicity of the structural design and theoretical methods make this proposed barrier a good candidate for applications with a known desired attenuation spectrum.
Article
Acoustics
Abhishek Gautam, Alper Celik, Mahdi Azarpeyvand
Summary: This study explores the acoustic performance of double degree of freedom Helmholtz resonators and multi-cell acoustic liners made from these resonators. The results suggest that increasing the volume ratio can enhance the sound absorption bandwidth, which is supported by the finite element analysis results.
Article
Materials Science, Multidisciplinary
Mariia Krasikova, Sergey Krasikov, Anton Melnikov, Yuri Baloshin, Steffen Marburg, David A. Powell, Andrey Bogdanov
Summary: This study develops the concept of a metahouse chamber for multiple band noise insulation, using a ventilated structure based on the idea of metamaterial systems. Broad stop-bands are achieved through strong coupling between pairs of Helmholtz resonators in the structure, demonstrating an averaged transmission attenuation of -18.6 dB within the spectral range from 1500 to 16 500 Hz both numerically and experimentally. The sparseness of the structure and the possibility of using optically transparent materials suggest the potential for partial optical transparency depending on the arrangement of structural elements.
ADVANCED MATERIALS TECHNOLOGIES
(2023)
Article
Instruments & Instrumentation
Lei Han, Hongli Ji, Jinhao Qiu
Summary: This paper proposes a modified theory for synthesizing the acoustic impedance of an absorbing panel by considering the interference among parallel absorbers. The results of validation on different absorbing panels and the comparison with the mutual-radiation-impedance method show that the modified theoretical model is better at predicting the absorption coefficient than is the traditional theory.
REVIEW OF SCIENTIFIC INSTRUMENTS
(2021)
Article
Mechanics
Xu Qiang, Peng Wang, Yingzheng Liu
Summary: The transient vortex dynamics within a microsecond-level acoustic cycle in an orifice-cavity structure subjected to high-intensity acoustic waves were numerically investigated. The results showed that the periodic production of vortex kinetic energy contributed more to the sound attenuation and the aeroacoustic energy analysis can provide insights into the acoustically induced vortex dynamics.
Review
Engineering, Aerospace
Qinghua Zeng, Xuanwu Chen
Summary: This paper analyzes the technical characteristics of the HTR combustor and proposes three major technical challenges. Systematic analysis and comprehensive discussion are conducted for each challenge, including technical strategies and research progress. The paper also presents current solutions and future research trends related to the technical limitations of the HTR combustor.
PROGRESS IN AEROSPACE SCIENCES
(2023)
Article
Acoustics
Lianchun Li, Yifan Diao, Haijun Wu, Weikang Jiang
Summary: Passive phase-controlled acoustic arrays based on metamaterial surfaces artificially manipulate acoustic waves, which have a wide range of applications. This study proposes an array based on Helmholtz resonators and labyrinth acoustic metamaterials, which achieves full phase control at a specific frequency through optimized thickness.
Article
Engineering, Aerospace
Qun Yan, Dongwen Xue, Qinqin Mu, Jiafeng Yang, Xiang Gao, Wenchao Huang
Summary: An aircraft nacelle acoustic liner plays a crucial role in reducing aircraft noise, and its design success relies heavily on the development of experimental technology. This study summarizes the impedance reduction technology and acoustic modal measurement and control technology for the design of an engine intake and exhaust ducts acoustic liner. The in-situ method shows higher accuracy at low frequencies while both methods have acceptable accuracy and applicability in the mid-frequency range. Comparatively, the seamless acoustic liner significantly improves noise reduction effect at multi-acoustic modes and target frequencies, achieving an overall reduction of up to 5.2 dB. Reliable and validated technologies of acoustic performance tests for a nacelle acoustic liner were established through this research.
Article
Physics, Multidisciplinary
WenQin Wang, XinSheng Fang, NengYin Wang, Yong Li, Tong Hao
Summary: This study reports the realization of acoustic double-zero-index metamaterials (DZIM) by coupling two identical Helmholtz resonators with a connecting channel. The system can generate independently tunable dipolar and virtually unchanged monopolar modes, allowing for simultaneous crossing of mass density and bulk modulus reciprocal zeros. Experimental results agree well with numerical calculations, and a broadband cloaking effect is demonstrated in a two-dimensional waveguide.
NEW JOURNAL OF PHYSICS
(2022)
Review
Chemistry, Multidisciplinary
George Karadimas, Konstantinos Salonitis
Summary: Ceramic matrix materials have gained significant attention for their material properties in engineering systems, particularly in aero-engine applications. High-temperature ceramics, especially ceramic matrix composites (CMCs), have shown great potential in reducing weight, increasing temperature capability, and minimizing cooling needs, thus improving efficiency. This paper focuses on evaluating the mechanical and thermal properties, classification, and manufacturing methods of available oxide and non-oxide CMCs through a literature survey. The research also presents a roadmap for the development of these materials to facilitate their broader adoption in aero-engine applications.
APPLIED SCIENCES-BASEL
(2023)
Article
Engineering, Aerospace
M. S. Escarti-Guillem, S. Hoyas, L. M. Garcia-Raffi
Summary: The acoustic pressure level and vibrations during lift-off of a launch vehicle can affect payload. Optimizing the plume deflector is an effective method to reduce noise. A study on the Vega launcher showed that different deflectors generate different acoustic waves, and the wedge deflector is more acoustically efficient.
Article
Physics, Multidisciplinary
Min Li, Jiuhui Wu
Summary: We present the design, simulation, and experimental testing of an acoustic metasurface made from an array of low-flow-sensitivity Helmholtz resonators (LFSHRs). This metasurface shows low sensitivity to changes in fluid flow, which can be attributed to the increase in flow velocity and acoustic mass inside the resonators. Compared to the traditional Helmholtz resonator, the impedance peak caused by increasing fluid flow can be reduced by more than 70.5% in magnitude and 93.8% in frequency using this metasurface.
Article
Thermodynamics
Chaojun Wang, Hongyuan Di, Hongjun Lin, Shoutang Shang, Lixin Yang
Summary: This study investigated the effects of radiation on combustion in an experimental aero-engine using the weighted-sum-of-gray-gas (WSGG) model. The results showed that radiation had negligible impacts on temperature and species concentrations, but significantly increased the temperature of the combustor liner walls in the primary zone. Furthermore, radiation from gas-soot mixture led to more uniform temperature distribution compared to radiation from gas only or no radiation.
APPLIED THERMAL ENGINEERING
(2024)
