Wyniki wyszukiwania - Biblioteka Nauki

1

A Hybrid Finite Element Method – Kirchhoff Approximation Method for Modeling Acoustic Scattering from an Underwater Vehicle Model with Alberich Coatings with Periodic Internal Cavities

100%

Yang F. , Peng Z. , Song H. , Tang Y. , Miao X.

Archives of Acoustics

|

2024

|

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.

2

Research on the Acoustic Scattering Characteristics of Multi-Sections Conning Tower Geometries in Monostatic Configuration

100%

Han L.-J. , Song H. , Chen C.-X. , Peng X.-R. , Peng Z.-l.

Archives of Acoustics

|

2022

|

tom Vol. 47, No. 3

307--317

EN

The overall acoustic echo of a submarine is greatly dependent on the conning tower. For enhancing the acoustic stealth performance of a submarine, it is necessary to research an innovative design scheme of the conning tower to reduce its target strength (TS). The aim of this work is to reduce the TS of a conning tower by varying its geometry and streamlining. The accuracy in modelling the acoustic scattering of a conning tower using the Kirchhoff approximation (KA) was validated, compared with finite element analysis (FEA). Several angular conning tower geometries were designed to analyze the effect of streamlining and the number of lateral facets on TS using the KA method. In consideration of the actual situation, the acoustic effect of backing medium was analyzed by compared water-filled elastic hulls with rigid hulls. From the observed TS calculation results, it is shown that the non-streamlined four lateral-facet conning tower geometries are optimal for acoustic stealth performance during the range of incidence angles from −10° to 10°, whereas the streamlined versions have better performance at incidence angles beyond this range. Furthermore, elastic hulls and rigid hulls provide similar spatial distribution regularities in monostatic configuration with the rigidity affecting the magnitude of the TS.

3

Review of research results concerning the modelling of shipping noise

86%

Yan X. , Song H. , Peng Z. , Kong H. , Cheng Y. , Han L.

Polish Maritime Research

|

2021

|

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.

4

Dynamic mechanical characteristics of filling layer self-compacting concrete under impact loading

72%

Li N. , Long G. , Fu Q. , Song H. , Ma C. , Ma K. , Xie Y. , Li H.

Archives of Civil and Mechanical Engineering

|

2019

|

tom Vol. 19, no. 3

851--861

EN

Filling layer self-compacting concrete (FLSCC) is a key construction material in China Rail Track System (CRTS) III slab ballastless track and its resistance to impact loading is of great importance to the service security of high-speed train. In this paper, the dynamic mechani-cal characteristics of FLSCC under impact loading were investigated with a split Hopkinson pressure bar (SHPB) at strain rates ranging from 101 s_1 to 102 s_1. Results show that the compressive strength, peak strain, elastic modulus and toughness ratio of FLSCC all increase with strain rate. The increase factors of compressive strength (DIFc) and strain (DIFe) of FLSCC increase linearly with decimal logarithm of strain rate. The elastic modulus (Ed) and toughness ratio (TR) increase linearly with strain rate. Self-compacting concrete (SCC) shows greater strain rate effect than normal concrete (NC). However, FLSCC presents lower strain rate effect but better toughness performance than normal SCC. The incorporation of large content of SP and VMA provides FLSCC with higher porosity, which makes it possess excellent dynamic mechanical performance.