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1
Content available Time-Domain Analysis of Echoes from Solid Spheres and Spherical Shells with Separated Transmit-Receive Configurations
100%
Wang Z. , Peng Z. , Zhou F. , Tang L.
Archives of Acoustics
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2024
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tom Vol. 49, nr 4
565--574
EN
The complexity of bistatic echo pulse sequences surpasses that of monostatic echo pulse sequences. Based on the scattering acoustic field of elastic spheres and spherical shells, a method is employed to calculate the time-domain echoes of solid spheres and spherical shells with transceiver separation under the condition of plane wave incidence. This is achieved by constructing the incident signal and performing a multiplication operation in the frequency domain with the target scattering acoustic field. Employing the contour integral method, we derive phase velocity and group velocity dispersion curves for circumferential waves propagating around these structures. Furthermore, under the assumption of plane wave incidence, we analyze the propagation paths of Rayleigh echoes for solid spheres and anti-symmetric Lamb waves for spherical shells. Estimation formulas for the arrival times of separated transmit-receive echoes are provided for both solid spheres and spherical shells. Our findings indicate that bistatic waves can be classified into clockwise and counterclockwise circulation patterns around the surfaces of these structures. Through a comparison with the time-angle spectrum of echoes, we demonstrate the accuracy of the proposed estimation formulas for echo arrival times. This study offers valuable insights for the identification of underwater targets.
2
Content available Prediction Method and Characteristics of Static Acoustic Scattering for Marine Composite Propellers
88%
Xu S. , Peng Z. , Zhou F. , Miu X. , Ke H.
Archives of Acoustics
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2024
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tom Vol. 49, nr 4
575--589
EN
This study introduces a hybrid approach to predict the acoustic scattering characteristics of composite propellers featuring variable thickness and complex curvature. The approach combines the Kirchhoff approximation (KA), which employs an intersection algorithm (IA) for determining the thickness of discrete surface elements, with the theory of orthotropic laminate transfer matrix (OLTM). The overall scattered sound field of the target is determined by solving the reflection coefficients of each surface element. To enhance computational efficiency, the scattered sound field of a complete composite propeller is ingeniously predicted by cloning mesh topology from a single propeller blade, taking advantage of the rotation symmetry characteristics of the composite propeller. The validity of this prediction method is confirmed through the finite element method (FEM) and static acoustic scattering characteristic experiments conducted on a lake. The predicted results for the target strength (TS) of the composite propeller closely align with the FEM. Additionally, the TS and time-domain echo characteristics of the steel propeller utilizing the KA exhibit strong agreement with the experimental findings. These research findings provide a significant reference value for predicting the acoustic scattering characteristics near the stern of underwater vehicles.
3
Content available Observation and Modelling on the Shipping Noise in Shallow Waters with Complex Islands and Reefs of the East China Sea
88%
Peng Z. , Zhou F. , Fan J. , Wang B. , Wen H.
Archives of Acoustics
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2021
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tom Vol. 46, No. 2
301--311
EN
The impact of the noise radiated from merchant ships on marine life has become an active area of research. In this paper, a methodology integrating observation at a single location and modelling the whole noise field in shallow waters is presented. Specifically, underwater radiated noise data of opportunistic merchant ships in the waters of Zhoushan Archipelago were collected at least one day in each month from January 2015 to November 2016. The noise data were analyzed and a modified empirical spectral source level (SSL) model of merchant ships was proposed inspired by the RANDI-3 model (Research Ambient Noise Directionality) methodology. Then combining the modified model with the realistic geoacoustic parameters and AIS data of observed merchant ships, the noise mappings in this area were performed with N × 2D of Normal Mode calculations, in which the SSL of each ship was estimated using the modified model. The sound propagation at different receiving positions is different due to the shielding effect of islands and bottom topography. The methodology proposed in this paper may provide a reference for modelling shipping noise in shallow waters with islands and reefs.
4
Content available A Hybrid Finite Element Method – Kirchhoff Approximation Method for Modeling Acoustic Scattering from an Underwater Vehicle Model with Alberich Coatings with Periodic Internal Cavities
88%
Yang F. , Peng Z. , Song H. , Tang Y. , Miao X.
Archives of Acoustics
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2024
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tom Vol. 49, nr 2
209--219
EN
Anechoic tiles can significantly reduce the echo intensity of underwater vehicles, thereby increasing the difficulty of detecting such vehicles. However, the computational efficiency of conventional methods such as the finite element method (FEM) and the boundary element method (BEM) has its limitations. A fast hybrid method for modeling acoustic scattering from underwater vehicles with anechoic tiles with periodic internal cavities, is developed by combining the Kirchhoff approximation (KA) and FEM. The accuracy and rapidity of the KA method were validated by FEM. According to the actual situation, the reflection coefficients of rubber materials with two different structures under rigid backing are simulated by FEM. Using the KA method, the acoustic scattering characteristics of the underwater vehicle with anechoic tiles are obtained by inputting the reflection coefficients and the target’s geometric grid. Experiments on the monostatic target strength (TS) in the frequency range of 1 to 20 kHz and time domain echo characteristics of acoustic scattering on a benchmark scale model with anechoic tiles are conducted. The research results indicate that the TS values and echo characteristic curves of the KA solutions closely approximate the experimental results, which verifies the accuracy of the KA method in calculating the TS and echo characteristics of underwater vehicles with anechoic tiles.
5
Content available Research on the modified echo highlight model for underwater vehicles with combined structures
75%
Xie X. , Liu F. , Jin G. , Liu J. , Xu C. , Peng Z.
Polish Maritime Research
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2023
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tom nr 3
163--173
EN
The highlight model is widely used as a simple and convenient method in the radar field but its accuracy is not high. Based on the traditional highlight model, the algorithm has been improved to address the acoustic scattering problems of underwater vehicles with more complex line shapes. The basic idea is to partition the model into micro-bodies to calculate the scattered sound pressure, consider the phase interference of each part, and then synthesise the scattered sound pressure to approximate the target’s actual shape. A computational model of the wedge-shaped convex structure on the back of the underwater vehicles is developed using a highlight model of a trapezoidal plate. The results of the calculations using the highlight model approach are consistent with those of the planar element method. Utilising the modified highlight model method, the accuracy of acoustic scattering characteristics calculations for the stern and overall structures of underwater vehicles has proven satisfactory. Finally, fast acoustic scattering prediction software is developed for underwater vehicles, enabling the calculation of the acoustic scattering characteristics for individual structures, combined structures, and coated silent tiles. This software provides algorithmic support for the fast prediction of the acoustic stealth performance of underwater vehicles.
6
Content available Experimental study and numerical simulation of radiated noise from unmanned underwater vehicle
75%
Zhang C. , Xu Q. , Yang H. , Peng Z. , Li J. , Zhou J.
Polish Maritime Research
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2024
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tom nr 4
131--141
EN
This paper focuses on the research of the radiation noise of underwater unmanned vehicle (UUV), which is one of the most important indicators for evaluating the performance of underwater unmanned equipment. Integrating experimental study and numerical calculations, this paper investigates the underwater radiated noise characteristics and hydrodynamic properties of the propeller of UUV. Firstly, an open-water radiated noise experiment is conducted. To ensure the accuracy of acoustic test, the UUV are held stationary during the experiment. Then, the hydrodynamic performance of a propeller in a steady flow field is calculated using Computational Fluid Dynamics (CFD). Finally, the noise in the unsteady flow field is calculated using the Ffowcs Williams-Hawkings (FW-H) equation. The results show that the propeller, as the main noise source when the UUV is working, exhibits distinct characteristic line spectra in the frequency response curve. By comparing the numerical and experimental results, it was found that the overall trend of the sound pressure level is similar. But the line spectrum characteristics of the numerical results between 100 and 400 Hz are more obvious, mainly because the simulation model is more idealized compared to the experimental tests. The study further examines the hydrodynamic characteristics, propeller noise, and directional characteristics of UUV under different operating conditions.
7
Content available Modulation Mechanism of Acoustic Scattering in Underwater Corner Reflectors with Acoustic Metasurfaces
75%
Du J. , Peng Z. , Ge L. , Lyu S. , Zhou F. , Liu Y.
Archives of Acoustics
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2023
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tom Vol. 48, No. 4
465--473
EN
Using the tunderwater corner reflector (CR) to simulate the acoustic scattering characteristics of the military target is a new technology to counter active sonar detection. Existing underwater CRs only have the ability to interfere with the acoustic field, but have limitations in acoustic wave modulation. Therefore, acoustic metasurfaces applied on CRs to enhance the ability of acoustic wave modulation has a great application prospect. A fast prediction method based on the Kirchhoff approximation (KA) and the ray tracing theory is proposed to calculate the acoustic scattering characteristics of CR with acoustic metasurfaces in grooves array type. The accuracy of the method is verified by the finite element method (FEM) simulation. The modulation effect of CR with grooves array in different gradient combinations on the structural scattering acoustic field is analyzed. The research shows that the CR with different combinations of the acoustic metasurface has an obvious modulation effect on the amplitude of the acoustic waves and the deflection of acoustic field. In particular, the grooves array in combination with positive and negative gradients has an obvious deflection impact on the scattering acoustic field.
8
Content available Review of research results concerning the modelling of shipping noise
75%
Yan X. , Song H. , Peng Z. , Kong H. , Cheng Y. , Han L.
Polish Maritime Research
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2021
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tom nr 2
102--115
EN
The effect of underwater radiated noise (URN) pollution (produced by merchant ships) on marine ecology has become a topic of extreme concern for both the academic community and the general public. This paper summarises some research results and modelling about shipping noise published over several decades, which comprises the research significance of low-frequency ambient noise and shipping noise, shipping noise source levels (SL), empirical models and the measurement standards of shipping noise. In short, we try to present an overall outline of shipping noise and ocean ambient noise for related research.
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