Numerical study of the acoustic properties of micro-perforated panels with tapered hole

2014 ◽  
Vol 62 (3) ◽  
pp. 152-159 ◽  
Author(s):  
Y.J. Qian ◽  
K. Cui ◽  
S.M. Liu ◽  
Z.B. Li ◽  
D.Y. Kong ◽  
...  
Keyword(s):  
Numerical Study ◽  
Acoustic Properties ◽  
Tapered Hole

scholarly journals Graphene-Based One-Dimensional Terahertz Phononic Crystal: Band Structures and Surface Modes

Nanomaterials ◽  
2020 ◽  
Vol 10 (11) ◽  
pp. 2205
Author(s):  
Ilyasse Quotane ◽  
El Houssaine El Boudouti ◽  
Bahram Djafari-Rouhani
Keyword(s):  
Free Surface ◽  
Sagittal Plane ◽  
Numerical Study ◽  
Phononic Crystal ◽  
Acoustic Properties ◽  
Band Structures ◽  
Surface Modes ◽  
Acoustic Modes ◽  
And Behavior ◽  
The Waves

In this paper, we provide a theoretical and numerical study of the acoustic properties of infinite and semi-infinite superlattices made out of graphene-semiconductor bilayers. In addition to the band structure, we emphasize the existence and behavior of localized and resonant acoustic modes associated with the free surface of such structures. These modes are polarized in the sagittal plane, defined by the incident wavevector and the normal to the layers. The surface modes are obtained from the peaks of the density of states, either inside the bulk bands or inside the minigaps of the superlattice. In these structures, the two directions of vibrations (longitudinal and transverse) are coupled giving rise to two bulk bands associated with the two polarizations of the waves. The creation of the free surface of the superlattice induces true surface localized modes inside the terahertz acoustic forbidden gaps, but also pseudo-surface modes which appear as well-defined resonances inside the allowed bands of the superlattice. Despite the low thickness of the graphene layer, and though graphene is a gapless material, when it is inserted periodically in a semiconductor, it allows the opening of wide gaps for all values of the wave vector k// (parallel to the interfaces). Numerical illustrations of the band structures and surface modes are given for graphene-Si superlattices, and the surface layer can be either Si or graphene. These surface acoustic modes can be used to realize liquid or bio-sensors graphene-based phononic crystal operating in the THz frequency domain.

scholarly journals Pulsed Ultrasound Assisted Thermo-Therapy for Subsurface Tumor Ablation: A Numerical Investigation

2021 ◽  
Vol 13 (4) ◽  
Author(s):  
Gajendra Singh ◽  
Abhijit Paul ◽  
Himanshu Shekhar ◽  
Anup Paul
Keyword(s):  
Focused Ultrasound ◽  
Numerical Study ◽  
Thermal Response ◽  
High Intensity Focused Ultrasound ◽  
Acoustic Properties ◽  
Pressure Amplitude ◽  
Thermal Dose ◽  
Pulsed Ultrasound ◽  
Layered Model

Abstract High-intensity focused ultrasound (HIFU) is a promising therapy for thermal ablation and hyperthermia, characterized by its non-invasiveness and high penetration depth. Effective HIFU thermo-therapy requires the ability to accurately predict temperature elevation and corresponding thermal dose distribution in target tissues. We report a parametric numerical study of the thermal response and corresponding of thermal dose in a soft tissue in response to ultrasound. We compared the predictions of tissue models with two, three, and seven layers, to ultrasound-induced heating at duty cycles ranging from 0.6 and 0.9. Further, two tumor sizes and transducer powers (10 W and 15 W) were considered. The inhomogeneous Helmholtz equation was coupled with the Pennes bio-heat equation to predict heating in response to pulsed ultrasound. Necrotic lesion size was calculated using the cumulative equivalent minute (CEM) thermal dose function. In-vitro experiments were performed with agar-based tissue phantoms as a preliminary validation of the numerical results. The simulations conducted with the seven-layered model predicted up to 33.5% lower peak pressure amplitude than the three-layered model. As the ultrasound pulse width decreased with the equivalent sonication time fixed, the corresponding magnitude of the peak temperature and the rate of temperature rise decreased. Pulsed ultrasound resulted in the increased volume of necrotic lesions for an equivalent time of sonication. The findings of this study highlight the dependence of HIFU-induced heating on target geometry and acoustic properties and could help guide the choice of suitable ultrasound exposure parameters for further studies.

Aeroacoustics of Open Cavities With Modified Geometry for Low Mach Number Flow

2015 ◽  
Author(s):  
Evren Yenigelen ◽  
Baha Zafer
Keyword(s):  
Subsonic Flow ◽  
Numerical Study ◽  
Leading Edge ◽  
Acoustic Properties ◽  
Sound Generation ◽  
Passive System ◽  
Low Mach Number ◽  
Open Cavities ◽  
Number Flow ◽  
Low Mach Number Flow

A numerical study using our source code to acquire the acoustic properties of subsonic flow past an open cavity with different modified geometries will be presented in this paper. A Modified Curle’s analogy will be applied to solve the far field acoustics of the flow. Several cases with different leading edge of cavity fillet radii will be analysed and the effects will be investigated. It is important to find a way to attenuate the sound generation by the cavity, as it is an undesired situation for most applications. In this work a passive system, fillet modification to the leading edge of the cavity, is suggested and the effects of it on the sound generation is investigated.

Numerical Study of the Acoustic Efficiency of Sound-Absorbing Structures with Resonators of Various Forms

2018 ◽  
Vol 931 ◽  
pp. 158-163 ◽  
Author(s):  
Pavel V. Pisarev ◽  
Aleksandr N. Anoshkin ◽  
Karina A. Maksimova
Keyword(s):  
Mathematical Model ◽  
Mathematical Models ◽  
Numerical Solution ◽  
Numerical Experiments ◽  
Numerical Study ◽  
Experimental Studies ◽  
Acoustic Properties ◽  
Acoustic Characteristics ◽  
The Difference ◽  
Comparison Of The Results

The present work is devoted to a numerical study of the acoustic characteristics of cubic and folded resonators of sound-absorbing structures (SAS). In the process of work, a physical statement of the problem and a mathematical model for predicting the effective acoustic properties of the SAS cells are formulated. The validation of the developed mathematical models was carried out. During the comparison of the results of a numerical solution with experimental studies, the difference did not exceed 3%. Based on the results of the numerical experiments, the most effective resonators were identified, and recommendations on the design of the SAS on their basis were formulated.

scholarly journals Numerical study of the acoustic efficiency of a group of Helmholtz resonators of various configurations

2018 ◽  
Vol 243 ◽  
pp. 00018 ◽  
Author(s):  
Pavel Pisarev ◽  
Aleksandr Anoshkin
Keyword(s):  
Mutual Influence ◽  
Numerical Study ◽  
Single Layer ◽  
Acoustic Properties ◽  
Mutual Arrangement ◽  
Resonant Frequencies ◽  
Helmholtz Resonators ◽  
Layer Composite ◽  
Model Channel ◽  
Physical And Mathematical Models

In this work the physical and mathematical models of predicting the effective acoustic properties of sound absorbing structures (Helmholtz resonators) in joint operation were formulated. Numerical simulation has been performed on the modeling of an acoustic wave in a model channel with resonators of various configurations. Research was carried out to optimize the mutual arrangement of Helmholtz cells (resonators) in sound-absorbing structures of resonant type. According to the results of the research, the mutual influence of closely located prismatic resonators in the model channel of rectangular shape was revealed. The most effective combinations of prismatic resonators were determined. Schemes and recommendations for the placement of composite and base resonators in sound-absorbing structures were developed. Unique single-layer composite sound-absorbing structures, working at several resonant frequencies, were developed.

Acoustic Properties of Artifical Larnyx Speech

1988 ◽  
Vol 16 ◽  
pp. 31-39
Author(s):  
Bethann Moffet ◽  
Rebekah Pindzola
Keyword(s):  
Acoustic Properties

Numerical study of the low-frequency atomic dynamics in a Lennard-Jones glass

1998 ◽  
Vol 77 (2) ◽  
pp. 473-484 ◽  
Author(s):  
M. Sampoli, P. Benassi, R. Dell'Anna,
Keyword(s):  
Numerical Study ◽  
Low Frequency ◽  
Lennard Jones
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