水下扁平阻抗结构衍射声场建模与计算

运用一致性几何衍射理论对水下扁平阻抗结构的衍射声场计算进行了理论建模与分析,并通过数值仿真讨论分析了水下扁平结构衍射声场分布与不同衍射类型、收发方式、结构表面阻抗特性、入射声波性质等几何特性和声学特性间的影响关系.其中,首次考虑了尖端衍射贡献影响,并重点分析了尖端衍射和结构表面阻抗特性在不同条件下对总的衍射声场作用规律和影响程度等.最后为验证上述理论模型和计算方法的正确性和可靠性,还与水下钢板散射声场分布实验测试结果进行了对比分析.研究结果表明:(1)考虑尖端衍射贡献影响使得上述模型更加完整,计算精度得到有效提高,且尖端衍射影响程度与入射声波频率、收发张角、结构表面阻抗特性以及声源、接收场点和结构的空间相对几何位置等因素有关;(2)结构两侧表面阻抗特性的影响规律和程度存在差异.其中,面向声源一侧的结构表面复反射系数幅值和背向声源一侧结构表面的复反射系数相角对结构衍射声场分布强度的影响尤为明显.这些对水下目标强度估计、自由场材料声学测试和衍射效应抑制技术研究等具有理论指导意义和工程应用价值.

Modeling and Calculating on the Diffraction Acoustic Field Originated from Underwater Flat Structure with Finite Impedance Surface

Theoretical modeling and analysis for the diffraction acoustic field originated from under-water fiat impedance structure are carried out with uniform geometrical theory of diffraction (UTD).The effecting relations between geometrical and acoustic characteristics are discussed by using nu-merical simulations. Different conditions include different types of diffraction, different emitting and receiving manners,different impedance characteristics of structure and different properties of inci-dent wave. The influence of vertex diffraction contribution is firstly considered in this paper, and the effect of vertex diffraction and the surface impedance characteristics of a structure on the total diffraction acoustic field under different conditions are emphasized. In order to verify the eorrectness and reliability of above theory model and calculating method,theoretical computing results are com-pared with tested data of the distributing characteristic of acoustic scattered field of underwater steel panel. The results show: (1) Considering vertex diffraction makes the above model more integrated and improves effectively computing accuracy,and effect of vertex diffraction depends on incident wave frequency, emitting and receiving manners, impedance characteristics of structure surface, and geometrical configuration relative to source, receiving position and structure, etc. (2) Effects of sur-face impedance characteristics of the structure on the two sides are different.Phase angle of complex reflection coefficient of facing with the sound source and magnitude value of complex reflection co-efficient of opposite to the sound source affect acoustic scattered field distribution greatly.These conclusions are very important and directive on theoretical research and engineering application in-eluding underwater target strength estimation,free field acoustic measurement for material and diffraction effect suppressing technique.