Design and optimization of low frequency multilayer absorbing materials

In the context of noise reduction in diverse applications where a shear grazing flow is present (i.e., engine nacelle, jet pump, landing gear), improved acoustic liner solutions are being sought. This is particularly true in the low-frequency regime, where space constraints currently limit the efficiency of classic liner technology. To perform the required multi-objective optimization of complex meta-surface liner candidates, a software platform called OPAL was developed. Its first goal is to allow the user to assemble a large panel of parallel/serial assembly of unit acoustic elements, including the recent concept of LEONAR materials. Then, the physical properties of this liner can be optimized, relatively to given weighted objectives (noise reduction, total size of the sample, weight), for a given configuration. Alternatively, properties such as the different impedances of liner unit surfaces can be optimized. To accelerate the process, different nested levels of optimization are considered, from 0D analytical coarse designs in order to reduce the parameter space, up to 2D plan or axisymmetric high-order Discontinuous Galerkin resolution of the Linearized Euler Equations. The presentation will focus on the different aspects of liner design considered in OPAL, and present an application on different samples made for a small scale aeroacoustic bench.

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Characterization and Design of Honeycomb Absorbing Materials

Solid State Phenomena ◽

10.4028/www.scientific.net/ssp.294.51 ◽

2019 ◽

Vol 294 ◽

pp. 51-56

Author(s):

Hui Min Sun ◽

Le Chen ◽

Zhao Zhan Gu

Keyword(s):

Double Layer ◽

Low Frequency ◽

Single Layer ◽

Electromagnetic Parameters ◽

Honeycomb Sandwich ◽

Absorbing Materials ◽

Absorbing Material ◽

The Difference ◽

Free Space Method ◽

Honeycomb Sandwich Structure

Honeycomb absorbing materials are anisotropic structural materials. Depending on the size of honeycomb lattices, the absorbent content of the impregnated layer is different, the thickness of the impregnated layer is different, and the absorbing function of the impregnated honeycomb absorbing materials is also different. For the characterization of electromagnetic parameters of honeycomb absorbing materials, this paper adopts free space method for testing, uses CST software for modeling, and inverts the electromagnetic parameters of honeycomb absorbing structures. The absorbing performance of single-layer and double-layer honeycomb sandwich structures was simulated by RAM Optimizer software. The research shows that the height of the single-layer honeycomb absorbing material is 22mm. When the absorber content is 65%, 75% and 85% respectively, the harmonic peak moves slightly to the low frequency electromagnetic wave with the increase of the absorber content, but the absorbing strength decreases with the increase of the absorber content. For the double-layer honeycomb sandwich structure, the difference of absorber content in the upper and lower honeycomb absorbing materials is smaller, and the absorbing performance is stronger. When the thickness of the wave-transparent panel is thinner, the harmonic peak of the absorbing curve moves slightly to the high frequency.

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Vibration Analysis and Experimental Research of the Linear-Motor-Driven Water Piston Pump Used in the Naval Ship

Shock and Vibration ◽

10.1155/2016/4608328 ◽

2016 ◽

Vol 2016 ◽

pp. 1-13

Author(s):

Ye-qing Huang ◽

Song-lin Nie ◽

Hui Ji ◽

Shuang Nie

Keyword(s):

Resonance Frequency ◽

Low Frequency ◽

Linear Motor ◽

Vibration Characteristics ◽

Piston Pump ◽

Response Analysis ◽

Design And Optimization ◽

Naval Ship ◽

Vibration Experiment ◽

Low Efficiency

Aiming at the existing problems of traditional water piston pump used in the naval ship, such as low efficiency, high noise, large vibration, and nonintelligent control, a new type of linear-motor-driven water piston pump is developed and its vibration characteristics are analyzed in this research. Based on the 3D model of the structure, the simulation analyses including static stress analysis, modal analysis, and harmonic response analysis are conducted. The simulation results reveal that the mode shape under low frequency stage is mainly associated with the eccentricity swing of the piston rod. The vibration experiment results show that the resonance frequency of linear-motor-driven water piston pump is concentrated upon 500 Hz and 800 Hz in the low frequency range. The dampers can change the resonance frequency of the system to a certain extent. The vibration under triangular motion curve is much better than that of S curve, which is consistent with the simulation conclusion. This research provides an effective method to detect the vibration characteristics and a reference for design and optimization of the linear-motor-driven water piston pump.

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Design and optimization of acoustic liners with a shear grazing flow: OPAL software platform description

INTER-NOISE and NOISE-CON Congress and Conference Proceedings ◽

10.3397/in-2021-1496 ◽

2021 ◽

Vol 263 (6) ◽

pp. 508-518

Author(s):

Frank Simon ◽

R. Roncen ◽

P. Vuillemin ◽

P. Klotz ◽

Fabien Méry ◽

...

Keyword(s):

Transmission Loss ◽

Low Frequency ◽

Total Sample ◽

Software Platform ◽

Linearized Euler Equations ◽

Design And Optimization ◽

Acoustic Liners ◽

Acoustic Liner ◽

Frequency Regime ◽

Grazing Flow

In the context of aircraft noise reduction in varied applications where a cold or hot shear grazing flow is present (i.e., engine nacelle, combustion chamber, jet pump, landing gear), improved acoustic liner solutions are being sought. This is particularly true in the low-frequency regime, where space constraints limit the efficiency of conventional liner technology. Therefore, liner design must take into account the dimensional and phenomenological characteristics of constituent materials, assembly specifications and industrial requirements involving multiphysical phenomena. To perform the single/multi-objective optimization of complex meta-surface liner candidates, a software platform coined OPAL (OPtimisation of Acoustic Liners) was developed. Its first goal is to allow the user to assemble a large panel of parallel/serial elementary acoustic layers along a given duct. Then, the physical properties of this liner can be optimized, relatively to weighted objectives, for a given flow and frequency range: impedance target, maximum absorption coefficient or transmission loss with a total sample size and weight... The presentation will focus on the different elementary bricks and assembly of a problem (from 0D analytical coarse designs in order to reduce the parameter space, up to 2D plan or axisymmetric high-order Discontinuous Galerkin simulations of the Linearized Euler Equations).

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Design and Optimization of Compact Printed Log-Periodic Dipole Array Antennas with Extended Low-Frequency Response

Electronics ◽

10.3390/electronics10172044 ◽

2021 ◽

Vol 10 (17) ◽

pp. 2044

Author(s):

Keyur K. Mistry ◽

Pavlos I. Lazaridis ◽

Zaharias D. Zaharis ◽

Tian Hong Loh

Keyword(s):

Frequency Response ◽

Low Frequency ◽

Trust Region ◽

Size Reduction ◽

Antenna Design ◽

Baseline Model ◽

Design And Optimization ◽

Novel Technique ◽

Array Antennas ◽

Lower Frequencies

This paper initially presents an overview of different miniaturization techniques used for size reduction of printed log-periodic dipole array (PLPDA) antennas, and then continues by presenting a design of a conventional PLPDA design that operates from 0.7–8 GHz and achieves a realized gain of around 5.5 dBi in most of its bandwidth. This antenna design is then used as a baseline model to implement a novel technique to extend the low-frequency response. This is completed by replacing the longest straight dipole with a triangular-shaped dipole and by optimizing the four longest dipoles of the antenna using the Trust Region Framework algorithm in CST. The improved antenna with extended low-frequency response operates from 0.4 GHz to 8 GHz with a slightly reduced gain at the lower frequencies.

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Study on Absorbing Properties of Honeycomb Absorbing Materials

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.815.645 ◽

2013 ◽

Vol 815 ◽

pp. 645-649

Author(s):

Hui Min Sun ◽

Zhao Zhan Gu ◽

Ran Ran Yang

Keyword(s):

Layer Thickness ◽

High Frequency ◽

Free Space ◽

Low Frequency ◽

Resonance Peak ◽

Test Method ◽

Electromagnetic Parameters ◽

Frequency Wave ◽

Absorbing Materials

Honeycomb absorbing materials were measured using the method of free space in this paper. The reflectance of honeycomb absorbing materials was calculated and simulated, and it was verified based on the measured results. It was demonstrated that this test method was feasible. Through studying on absorbing properties of honeycomb, the results have showed that the radar absorbing properties of honeycomb are related to electromagnetic parameters, as well as thickness of the dip-coatings. With the increase of thickness of the dipping layer, the radar absorbing capability of high frequency and low frequency wave are significantly increased. It is worth noting that the resonance peak moved to the low frequency with the increase of dipping layer thickness. These results are useful for design of honeycomb absorbing materials.

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