The Research On The Acoustic Characteristics Of Underwater Anechoic Coating By OOFEM

In this thesis, the acoustic characteristics of underwater anechoic coating are studied and analyzed by the OOFEM—Object-Oriented Finite Element Method. The modeling and calculating of structure problem is widely conducted with the help of the finite element method (FEM). For satisfying the Bloch periodic boundary condition, we found that FEM can effectively analyzed and calculated sound-absorbing coefficient and sound-transmitting coefficient. According to the symmetric relation of physical quantity such as displacement, the thesis had demonstrated that under the condition of normal incidence, the smallest analyzing model is the triangular prism; whose cross section is 1/36 of equilateral hexagon. This analysis model can largely reduce computation amount of finite element analysis.OOFEM is introduced into the finite element research for the acoustic characteristics of underwater anechoic coating; object-oriented finite element analysis software for the acoustic characteristics of underwater anechoic coating is programmed on Microsoft VC6.0, which is a beneficial attempt for the researches in this field. The object classes of the OOFEM for the acoustic characteristics of underwater anechoic coating are extracted, the relationships among them are constructed, and the software required is formed on the basis of the completion of the finite analysis message flow. The whole process includes the analysis, design and implementation of the OOFEM for the acoustic characteristics of underwater anechoic coating.The accuracy of the designed OOFEM software is proved through the comparison between the analytical solutions for both sound absorption coefficient and transmission coefficient of the acoustic wave propagating in stratified medium. The acoustic reflection characteristics of the underwater anechoic coating are numerical analyzed. The acoustic reflection coefficients of the underwater anechoic coating without cavity are calculated by changing the physical parameters of sound absorption material, the influence of the acoustic reflection characteristic caused by the thickness, density, young modulus, poisson ratio and loss factors of sound absorption material is analyzed. The resonant characteristics is calculated and analyzed in different backings. The acoustic reflection characteristics of the underwater anechoic coating with cavity are researched in different backings and cavity types, and effects of structure are also analyzed. It is hoped that OOFEM software can be expanded to more areas.