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Prediction Method and Characteristics of Static Acoustic Scattering for Marine Composite Propellers

100%

Xu S. , Peng Z. , Zhou F. , Miu X. , Ke H.

Archives of Acoustics

2024

tom Vol. 49, nr 4

575--589

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.

Observation and Modelling on the Shipping Noise in Shallow Waters with Complex Islands and Reefs of the East China Sea

100%

Peng Z. , Zhou F. , Fan J. , Wang B. , Wen H.

2021

tom Vol. 46, No. 2

301--311

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.

Modulation Mechanism of Acoustic Scattering in Underwater Corner Reflectors with Acoustic Metasurfaces

86%

Du J. , Peng Z. , Ge L. , Lyu S. , Zhou F. , Liu Y.

Archives of Acoustics

2023

tom Vol. 48, No. 4

465--473

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.