A modified planar elements method considering occlusion and secondary scattering
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摘要: 对外部加环肋圆柱壳体的声散射研究表明,部件之间的互散射(二次散射)对反向散射声场有重要贡献。本文在板块元算法基础上,加入对遮挡和二次散射的判段,得到修正的板块元算法。通过计算外部加环肋圆柱壳体的目标强度,展现了二次散射和遮挡效应在不同角度的交替作用;而在考虑透射效应后,在高频段和低频段呈现出不同的效果。修正板块元计算结果与实测数据比较,两者一致。Abstract: The scattering from the external ring-stiffened finite cylindrical shell has been studied before and the result shows the secondary scattering has important contribution to the scattering field.The primary Planar Elements Method (PEM)cannot accurately forecast the echo characteristics.In this paper,based on the primary PEM,a modified PEM is developed by adding the judgments of occlusion and secondary scattering and combining with the bistatic PEM.The Target Strength of the dihedral reflector is calculated both by the primary and modified PEM and then the validity of the modified PEM is shown by comparing with the theoretical solution.Then,the Target Strength of the external ring-stiffened finite cylindrical shell is also calculated.The result shows that occlusion and secondary scattering respectively have important contribution to the scattering field at different incident angle.When considering the transmission of the rings,the secondary scattering is strong in high-frequency but weak in low-frequency.Finally,the good agreement is shown between the numerical result and the experimental result.
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