scholarly journals Simulation Analysis of Cylindrical Shell Cavity Noise with Melamine Foam Lining

2021 ◽  
Vol 2021 ◽  
pp. 1-9
Author(s):  
Menghui Qi ◽  
Bin Li ◽  
Shilin Yan ◽  
Qinghua Yan ◽  
Qiyu He
Keyword(s):  
Cylindrical Shell ◽  
Noise Reduction ◽  
Simulation Analysis ◽  
Cylindrical Shells ◽  
Element Model ◽  
Measured Data ◽  
Frequency Noise ◽  
Precision Instrument ◽  
Different Thickness ◽  
Melamine Foam

To solve the problem of the harsh midlow frequency noise of rocket fairing, the cylindrical section of the protective precision instrument fairing is simplified as cylindrical shells, and different lining strategies of melamine foam (MF) are studied experimentally and numerically. Based on Virtual.Lab Acoustic software, a finite element model of the cylindrical cavity is established, and the correctness is verified by comparison with the measured data. On that basis, the influences of the lining position of different thickness MF on the noise reduction of cylindrical shells are investigated. It is shown that the thickness and location of the laying material have a significant effect on the noise reduction at the same specific gravity.

scholarly journals Experiment and Simulation Analysis on Noise Attenuation of Al/MF Cylindrical Shells

2017 ◽  
Vol 2017 ◽  
pp. 1-8
Author(s):  
Bin Li ◽  
Jian Li ◽  
Shilin Yan ◽  
Wenjie Yan ◽  
Xu He
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Noise Reduction ◽  
Control Method ◽  
Simulation Analysis ◽  
Cylindrical Shells ◽  
Internal Noise ◽  
Element Model ◽  
Cavity Resonance ◽  
Noise Attenuation

For the issue concerning internal noise reduction of Al-made cylindrical shell structure, the noise control method of laying melamine foam (MF) layer is adopted for in-shell noise attenuation experiments of Al and Al/MF cylindrical shells and corresponding internal noise response spectrograms are obtained. Based on the Virtual.Lab acoustics software, a finite element model is established for the analysis of noise in the Al/MF cylinder shell and numerical simulation computation is conducted for the acoustic mode and in-shell acoustic response; the correctness of the finite element model is verified via comparison with measured data. On this basis, influence rules of different MF laying rate and different laying thickness on acoustic cavity resonance response within the low and medium frequency range of 100–400 Hz are studied. It is indicated that noise reduction increases with MF laying rate, but the amplification decreases along with the rising of MF laying rate; noise reduction per unit thickness decreases with the increase of laying thickness, while noise reduction per unit area increases.

Experimental Study on Pre-Stressed Circular Cylindrical Shell

2012 ◽  
Author(s):  
Antonio Zippo ◽  
Marco Barbieri ◽  
Matteo Strozzi ◽  
Vito Errede ◽  
Francesco Pellicano
Keyword(s):  
Experimental Study ◽  
Cylindrical Shell ◽  
Axial Load ◽  
Nonlinear Vibrations ◽  
Circular Cylindrical Shell ◽  
Cylindrical Shells ◽  
Experimental Studies ◽  
Element Model ◽  
Experimental Setup ◽  
Circular Cylindrical Shells

In this paper an experimental study on circular cylindrical shells subjected to axial compressive and periodic loads is presented. Even though many researchers have extensively studied nonlinear vibrations of cylindrical shells, experimental studies are rather limited in number. The experimental setup is explained and deeply described along with the analysis of preliminary results. The linear and the nonlinear dynamic behavior associated with a combined effect of compressive static and a periodic axial load have been investigated for different combinations of loads; moreover, a non stationary response of the structure has been observed close to one of the resonances. The linear shell behavior is also investigated by means of a finite element model, in order to enhance the comprehension of experimental results.

Computer Simulation of Cylindrical Shell Penetrated by Rigid Projectile

2012 ◽  
Vol 152-154 ◽  
pp. 594-598
Author(s):  
Xue Hui Yu ◽  
Zhi Jun Han ◽  
Zuo Yi Kang ◽  
Guo Yun Lu ◽  
Zhi Fang Liu
Keyword(s):  
Computer Simulation ◽  
Cylindrical Shell ◽  
Energy Distribution ◽  
Critical Speed ◽  
Cylindrical Shells ◽  
Great Influence ◽  
Geometric Parameters ◽  
Lateral Impact ◽  
Rigid Projectile ◽  
Different Thickness

Computer simulation of cylindrical shell subject to lateral impact by rigid projectile is carried out. The effects of three kinds of typical rigid projectiles, geometric parameters of cylindrical shell and constraint conditions on critical speed are analyzed. The results indicate that the shape of projectile and size of cylindrical shell have a great influence on penetration, and the tapered projectile has a minimum critical speed. The influence of constraint conditions on penetration has a great relationship with thickness of cylindrical shells; energy distribution varies with different thickness of cylindrical shells.

Numerical study on the airfoil self-noise of three owl-based wings with the trailing-edge serrations

2021 ◽  
pp. 095441002098822
Author(s):  
Dian Li ◽  
Xiaomin Liu ◽  
Lei Wang ◽  
Fujia Hu ◽  
Guang Xi
Keyword(s):  
Flow Field ◽  
Noise Reduction ◽  
Numerical Study ◽  
Barn Owl ◽  
Aerodynamic Noise ◽  
Frequency Noise ◽  
Trailing Edge ◽  
Reduction Mechanisms ◽  
Trailing Edge Serrations ◽  
Bionic Airfoil

Previous publications have summarized that three special morphological structures of owl wing could reduce aerodynamic noise under low Reynolds number flows effectively. However, the coupling noise-reduction mechanism of bionic airfoil with trailing-edge serrations is poorly understood. Furthermore, while the bionic airfoil extracted from natural owl wing shows remarkable noise-reduction characteristics, the shape of the owl-based airfoils reconstructed by different researchers has some differences, which leads to diversity in the potential noise-reduction mechanisms. In this article, three kinds of owl-based airfoils with trailing-edge serrations are investigated to reveal the potential noise-reduction mechanisms, and a clean airfoil based on barn owl is utilized as a reference to make a comparison. The instantaneous flow field and sound field around the three-dimensional serrated airfoils are simulated by using incompressible large eddy simulation coupled with the FW-H equation. The results of unsteady flow field show that the flow field of Owl B exhibits stronger and wider-scale turbulent velocity fluctuation than that of other airfoils, which may be the potential reason for the greater noise generation of Owl B. The scale and magnitude of alternating mean convective velocity distribution dominates the noise-reduction effect of trailing-edge serrations. The noise-reduction characteristic of Owl C outperforms that of Barn owl, which suggests that the trailing-edge serrations can suppress vortex shedding noise of flow field effectively. The trailing-edge serrations mainly suppress the low-frequency noise of the airfoil. The trailing-edge serration can suppress turbulent noise by weakening pressure fluctuation.

scholarly journals Shape Factors in Low‐Frequency Noise Reduction

1967 ◽  
Vol 42 (5) ◽  
pp. 1202-1203
Author(s):  
J. Ronald Bailey ◽  
Franklin D. Hart
Keyword(s):  
Noise Reduction ◽  
Low Frequency ◽  
Frequency Noise ◽  
Low Frequency Noise ◽  
Shape Factors

Acoustic Radiation From Thick Laminated Cylindrical Shells With Sparse Cross Stiffeners

2013 ◽  
Vol 135 (3) ◽  
Author(s):  
Xiongtao Cao ◽  
Chao Ma ◽  
Hongxing Hua
Keyword(s):  
Cylindrical Shell ◽  
Radial Displacement ◽  
Acoustic Radiation ◽  
Periodic Structures ◽  
Cylindrical Shells ◽  
Acoustic Power ◽  
Acoustic Energy ◽  
Parallel Plates ◽  
Wavenumber Domain ◽  
Laminated Cylindrical Shells

A general method for predicting acoustic radiation from multiple periodic structures is presented and a numerical solution is proposed to find the radial displacement of thick laminated cylindrical shells with sparse cross stiffeners in the wavenumber domain. Although this method aims at the sound radiation from a single stiffened cylindrical shell, it can be easily adapted to analyze the vibrational and sound characteristics of two concentric cylindrical shells or two parallel plates with complicated periodic stiffeners, such as submarine and ship hulls. The sparse cross stiffeners are composed of two sets of parallel rings and one set of longitudinal stringers. The acoustic power of large cylindrical shells above the ring frequency is derived in the wavenumber domain on the basis of the fact that sound power is focused on the acoustic ellipse. It transpires that a great many band gaps of wave propagation in the helical wave spectra of the radial displacement for stiffened cylindrical shells are generated by the rings and stringers. The acoustic power and input power of stiffened antisymmetric laminated cylindrical shells are computed and compared. The acoustic energy conversion efficiency of the cylindrical shells is less than 10%. The axial and circumferential point forces can also produce distinct acoustic power. The radial displacement patterns of the antisymmetric cylindrical shell with fluid loadings are illustrated in the space domain. This study would help to better understand the main mechanism of acoustic radiation from stiffened laminated composite shells, which has not been adequately addressed in its companion paper (Cao et al., 2012, “Acoustic Radiation From Shear Deformable Stiffened Laminated Cylindrical Shells,” J. Sound Vib., 331(3), pp. 651-670).

EFFECTS OF QUANTUM CONFINEMENT ON LOW FREQUENCY NOISE IN δ-DOPED GaAs STRUCTURES GROWN BY MBE

2002 ◽  
Vol 02 (01) ◽  
pp. L37-L45
Author(s):  
X. Y. CHEN ◽  
P. M. KOENRAAD
Keyword(s):  
Quantum Confinement ◽  
Low Frequency ◽  
Frequency Noise ◽  
Low Frequency Noise ◽  
Free Carriers ◽  
In Doping ◽  
Three Samples ◽  
Different Temperatures ◽  
Lower Magnitude ◽  
Different Thickness

Low frequency noise (LFN) was measured in δ-doped GaAs structures in which the free carriers are confined to a 2-dimensional plane. Three samples grown at different temperatures, resulting in doping layers of a different thickness, are used to study the effects of quantum confinement on the LFN. We observed both 1/f noise and generation-recombination noise components. We find that a stronger quantum confinement results in a bigger Hall mobility and a lower magnitude of the 1/f noise.

Application of a Helmholtz structure for low frequency noise reduction

2015 ◽  
Vol 63 (1) ◽  
pp. 20-35 ◽  
Author(s):  
Dong Guan ◽  
Jiu Hui Wu ◽  
Li Jing ◽  
Nansha Gao ◽  
Mingming Hou
Keyword(s):  
Noise Reduction ◽  
Low Frequency ◽  
Frequency Noise ◽  
Low Frequency Noise
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