Effects of Quay Wall and Seabed Reflection on the AUV Acoustic Radiation Test Analysis

2014 ◽  
Vol 599-601 ◽  
pp. 922-926
Author(s):  
Guo Liang Xu ◽  
Qi Wei He ◽  
Shao Chun Ding ◽  
Hai Bo Wan
Keyword(s):  
Acoustic Field ◽  
Field Test ◽  
Sound Pressure ◽  
Acoustic Radiation ◽  
Near Field ◽  
Test Analysis ◽  
Complex Sound ◽  
Quay Wall ◽  
Radiation Test ◽  
Acoustical Holography

To analyze effects of quay environment on the AUV radiated acoustic field test, the PNAH (PNAH: planar near-field acoustical holography) was used to simulate acoustic field. By simulating the free and non-free acoustic field and comparing amplitudes and angles of complex sound pressure, Analyze effects of quay wall and seabed reflection on the AUV radiated acoustic field test to determine the standard of quay wall and seabed environment which meets testing. The work would provide a certain reference for the AUV radiated acoustic field test.

scholarly journals Structure-Acoustic Coupling Analysis of Vibration and Underwater Acoustic Radiation of a Ring-Stiffened Conical Shell

2021 ◽  
Vol 2021 ◽  
pp. 1-9
Author(s):  
Qingtao Gong ◽  
Zhanyang Chen ◽  
Hongbin Gui ◽  
Dong Yu
Keyword(s):  
Acoustic Field ◽  
Conical Shell ◽  
Sound Pressure ◽  
Field Model ◽  
Acoustic Radiation ◽  
Rear Side ◽  
The Finite Element Method ◽  
Underwater Acoustic ◽  
Acoustic Coupling ◽  
Element Method

The underwater acoustic radiation of the submarine power cabin has recently become a hot topic in the industry and also in the academia. In this article, the vibration and underwater acoustic radiation of a ring-stiffened conical shell with bases are investigated numerically by means of the combination of the finite element method and boundary element method. The acoustic radiation field is obtained by the traditional acoustic field model and ISO acoustic field model, respectively. A series of numerical examples are given, and the results are compared. Besides, the sound pressure at different positions with frequency is further studied. It is shown that the sound radiated by the structure mainly propagates to the side directions of the shell and propagates relatively less to the front side and the rear side.

Simulation and experimental investigations for the patch near-field acoustical holography

2008 ◽  
Vol 222 (6) ◽  
pp. 945-953 ◽  
Author(s):  
C Yang ◽  
J Chen ◽  
J Q Li ◽  
W F Xue
Keyword(s):  
Fourier Transform ◽  
Sound Pressure ◽  
Near Field ◽  
Sound Field ◽  
Experimental Investigations ◽  
Regularization Methods ◽  
Aperture Size ◽  
Measurement Surface ◽  
Physical Necessity ◽  
Acoustical Holography

In order to reconstruct the sound field, the fast Fourier transform (FFT)-based near-field acoustical holography (NAH) demands that the measurement surface must extend to a region where the sound pressure decreases to a low level. This method is unfit for reconstructing the partial sound field in which the measurement aperture size is limited either by physical necessity or as a way of reducing the measurement cost. Statistically optimal NAH (SONAH) performs plane-to-plane calculations directly in the spatial domain, avoids all errors occurred in the FFT-based NAH and significantly increases the accuracy of the reconstruction of the partial sound field. In the present work, combined with the different regularization methods, SONAH is performed for reconstructing the partial sound field. The errors over the central and the peripheral sections of the reconstruction area are researched separately. Simulations and experiments show that SONAH is successful in reconstructing the partial sound field and the errors over the central sections are smaller than that over the peripheral sections. Experiments demonstrate that Tikhonov regularization in conjunction with Engl's criterion is suitable for the reconstruction of the practical sound field.

Near-Field Acoustic Holography of Cyclostationary Sound Field

2013 ◽  
Vol 631-632 ◽  
pp. 1318-1323
Author(s):  
Min Peng
Keyword(s):  
Time Series ◽  
Sound Pressure ◽  
Near Field ◽  
Sound Field ◽  
Rotating Machinery ◽  
Stationary Field ◽  
Acoustic Holography ◽  
Complex Sound ◽  
Radiated Sound ◽  
Slice Method

The radiated sound field of rotating machinery or reciprocating machinery has a significant periodically time-variant nature. This is a kind of non-stationary sound field and called cyclostationary sound field. In the conventional planar near-field acoustic holography(PNAH), this kind of sound field is treated as stationary field, so the information relating to the change of frequency with time will be loss inevitably. In this article, the cyclic spectral density(CSD) instead of the complex sound pressure was adopted as reconstructing physical quantity in the PNAH, and the cyclostationary PNAH(CPNAH) technique was proposed. Meanwhile, focusing on the calculation complex of CSD and the accuracy of the cyclic nature extracted, the gathering slice method of CSD was proposed by referring time aliasing methods on time series. The experiment results illustrate that the cyclic nature of cyclostationary sound field may be extracted directly and the location of the source determined exactly as well.

Research on the Planar Near-Field Acoustic Holography for Cyclostationary Sound Field

2011 ◽  
Vol 105-107 ◽  
pp. 164-167
Author(s):  
Zhi Min Chen ◽  
Hai Chao Zhu ◽  
Rong Fu Mao
Keyword(s):  
Spectral Density ◽  
Physical Quantity ◽  
Sound Source ◽  
Sound Pressure ◽  
Near Field ◽  
Sound Field ◽  
Rotating Machines ◽  
Carrier Wave ◽  
Acoustic Holography ◽  
Complex Sound

The conventional planar near-field acoustic holography is not suitable for cyclostationary sound field radiated by the rotating machines. When the cyclic spectral density (CSD), instead of the complex sound pressure, is adopted as reconstructed physical quantity, the modulating wave and carrier wave components of the cyclostationary sound field can be extracted exactly and so the cyclostationary planar near-field acoustic holography (CPNAH) technique was proposed. Simulation and experimental results show that the modulation characteristics of the cyclostationary sound field can be extracted effectively and the sound source can be localized accurately.

A new data extrapolation method based on the modified Helmholtz equation least-squares method

2012 ◽  
Vol 227 (6) ◽  
pp. 1252-1265
Author(s):  
R Wang ◽  
J Chen ◽  
GM Dong
Keyword(s):  
Helmholtz Equation ◽  
Least Squares ◽  
Acoustic Field ◽  
Least Squares Method ◽  
Acoustic Radiation ◽  
Near Field ◽  
Extrapolation Method ◽  
Modified Helmholtz Equation ◽  
Helmholtz Equation Least Squares ◽  
Data Extrapolation

Fast Fourier transform-based near-field acoustic holography requires that the measurement aperture should completely enclose the source, which is impractical for large-scale sound sources. Helmholtz equation least-squares method can reconstruct the acoustic field with fewer measurements than fast Fourier transform-based near-field acoustic holography. However, it is not suitable for reconstructing acoustic radiation from multiple sources or a complicated source which consists of several separated parts. To circumvent this difficulty and enhance the reconstruction accuracy, a new data extrapolation method based on the modified Helmholtz equation least-squares method is proposed. The base of this data extrapolation method is a modified Helmholtz equation least-squares method which expresses the acoustic field of a complicated source as the superposition of the acoustic radiation from all of its separated parts. Using the acoustic pressures reconstructed with the modified Helmholtz equation least-squares method, the measurement surface is extended through an iterative procedure. Meanwhile, Tikhonov regularization method together with generalized cross-validation parameter choice method is utilized to treat the ill-posed problem in reconstructions. In the end, taking the extrapolated pressures as input data, the acoustic field can be reconstructed more precisely. Numerical simulation and experimental results demonstrate that this method can significantly enhance the reconstruction accuracy and efficiency.

Effect on Measurement of the Radiated Acoustic Field of Underwater Structure Based on NAH with Swinging Measuring Surface

2012 ◽  
Vol 197 ◽  
pp. 778-781
Author(s):  
Lin Na Zhou ◽  
Shao Chun Ding ◽  
Ruo Yu Zhang ◽  
Jing Jun Lou ◽  
Shi Jian Zhu
Keyword(s):  
Sound Pressure ◽  
Power Level ◽  
Near Field ◽  
Sound Intensity ◽  
Sound Power ◽  
Mean Square ◽  
Sound Power Level ◽  
Measuring Surface ◽  
Underwater Structure ◽  
Acoustical Holography

This paper analyzes the effects of the swinging NAH(Near field Acoustical Holography) measuring array on measurement of the sound power level of underwater structure. We use the method of sound intensity integral, the method of mean square sound pressure and the method of NAH reversal pressure to calculate the sound power level under certain collection of frequency with measuring surface in different states. We also analyze the relative error of results acquired by those methods, which can help validating the reliability and the error estimate of the results calculated with NAH.

Coherent noise sources of a subsonic round jet investigated using hydrodynamic and acoustic phased-microphone arrays

2013 ◽  
Vol 730 ◽  
pp. 659-698 ◽  
Author(s):  
Takao Suzuki
Keyword(s):  
Acoustic Field ◽  
Sound Pressure ◽  
Generalized Inverse ◽  
Near Field ◽  
Beam Forming ◽  
Coherent Noise ◽  
Noise Sources ◽  
Array Data ◽  
Round Jet ◽  
Acoustic Array

AbstractBased on phased-microphone array data acquired in the past, properties of coherent noise sources in a subsonic round jet are investigated at low frequencies ($0. 2\lesssim \mathit{St}\lesssim 0. 6$) via two approaches: (i) by extracting hydrodynamic fluctuations from the near-field array, instability-wave components are projected to the acoustic field using a boundary-value problem technique; (ii) by post-processing mid-field array data in an acoustic field, noise sources are decomposed into multipole distributions using a generalized-inverse beam-forming technique. Comparison between the projected acoustic fields from the hydrodynamic array and the sound pressure levels at the acoustic array implies that the near-field pressure fluctuations beyond the end of the potential core primarily contribute to the downstream sound, as mentioned by many previous studies. However, the jet-spreading effect, which creates the streamwise growth and decay of the eigenfunctions in linear stability analysis, is insufficient to generate the sound pressure levels measured in the acoustic array. In the actual hydrodynamic data, the streamwise decay is much slower and the phase velocity is faster than those of the corresponding eigenfunction beyond the peak of the wave-packet, and these factors govern the downstream sound. Results from the acoustic array demonstrate that free-space multipole distributions detected by generalized-inverse beam-forming can reproduce primary coherent modes, the first one predominantly propagating downstream and the second one typically being more omni-directional. In particular, the detected phase relation of the first coherent mode shows nearly a constant slope, indicating a wavy-type source structure and the relation of downstream sound with instability waves.

scholarly journals Mathematical modeling and experimental study on solid–liquid suspension separation in ultrasonic standing wave field

2021 ◽  
pp. 146134842110229
Author(s):  
Yajing Wang ◽  
Liqun Wu ◽  
Yaxing Wang ◽  
Yafei Fan
Keyword(s):  
Standing Wave ◽  
Sound Pressure ◽  
Acoustic Radiation ◽  
Sound Field ◽  
Radiation Force ◽  
High Energy ◽  
Factors Affecting ◽  
Liquid Suspension ◽  
Ultrasonic Standing Wave ◽  
Solid Liquid

A new method of removing waste chips is proposed by focusing on the key factors affecting the processing quality and efficiency of high energy beams. Firstly, a mathematical model has been established to provide the theoretical basis for the separation of solid–liquid suspension under ultrasonic standing wave. Secondly, the distribution of sound field with and without droplet has been simulated. Thirdly, the deformation and movement of droplets are simulated and tested. It is found that the sound pressure around the droplet is greater than the sound pressure in the droplet, which can promote the separation of droplets and provide theoretical support for the ultrasonic suspension separation of droplet; under the interaction of acoustic radiation force, surface tension, adhesion, and static pressure, the droplet is deformed so that the gas fluid around the droplet is concentrated in the center to achieve droplet separation, and the droplet just as a flat ball with a central sag is stably suspended in the acoustic wave node.

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