复杂非水密结构目标强度预报方法研究

Target strength prediction method for complex non-watertight structure

为准确预报表面敷设声学覆盖层,内部含耐压圆柱体的非水密结构声目标强度,构建了一种新的参数反演方法。将遗传算法与非线性规划相结合,在考虑斜入射、多次散射、吻合效应以及横波波速阈值的情况下,利用分层介质理论建立了双层弹性介质层反演模型,以此替代含复杂内部结构的声学覆盖层,该反演模型与原结构在各个角度下均具有基本相同的反射系数与透射系数。进而,应用COMSOL Multiphysics软件建立表面敷设声学覆盖层,内部含耐压圆柱体的复杂非水密结构与外壳由两种反演材料组成的等效结构,并求其声散射特性。研究表明:收发合置情况下,原结构与等效结构目标强度值基本一致,各个方向入射时研究频段整体误差在1.5 dB以下;30°收发分置情况下,原结构与等效结构目标强度波峰波谷趋势相同,各个方向入射时研究频段整体误差在2 dB以下。中高频段,原结构与等效结构目标强度指向性吻合程度较好;中低频段,原结构与等效结构目标强度指向性基本一致,但幅值存在差异;总体来看,-30°~30°范围内,除个别频率外,原结构与等效结构目标强度基本吻合。

Here, to accurately predict strength of a non-watertight structural acoustic target with an acoustic coating on surface and a watertight cylinder inside, a new parameter inversion method was proposed and constructed. Combining genetic algorithm with nonlinear programming, considering oblique incidence, multi-scattering, coincidence effect and transverse wave velocity threshold, the inversion model of two-elastic medium layer was established by using the layered medium theory to replace the acoustic cover layer containing complex internal structure. The inversion model and the original structure could have basically the same reflection coefficients and transmission coefficients at all angles. Then, COMSOL Multiphysics software was used to establish a complex non-watertight structure with a watertight cylinder inside and an acoustic coating on its surface and an equivalent structure with outer shell composed of two inversion materials. The latter’s acoustic scattering characteristics were calculated. The study showed that under the condition of combined transceiver, target strength values of the original structure and the equivalent structure are basically the same, the overall error within the studied frequency band is below 1.5 dB during incidence in all directions;in the case of 30° transceiver separation, peak and valley trends of target strengths of the original structure and the equivalent structure are the same, and the overall error within the studied frequency band is below 2 dB during incidence in all directions;within middle and high frequency band, target strength directivities of the original structure and the equivalent structure agree better with each other;within middle and low frequency band, target strength directivities of the original structure and the equivalent structure are basically the same, but their amplitudes are different;in general, within the range of-30°~30°, except for individual frequencies, the target strength of the original structure is basically consistent to that of the equivalent structure.