水下扁平结构散射声场计算研究

Calculating Research on Estimating the Scatter Field Distribution for Underwater Flat Structure

出于拓展计算频域宽度角度考虑,该文提出一种基于积分方程法和几何衍射法为理论基础的可覆盖水声全部工作频段的水下扁平目标散射声场的宽频域混合计算模型,并以矩形钢板为目标,对其在不同声波入射角度条件下的水下散射声场频域分布开展了定量研究与讨论分析,并得出:两种方法在所求解频域内的计算结果均互为补充,在中频段吻合程度较好,吻合频点与收发位置和结构的几何配置等因素有关;散射声场频域分布特征与各成分波间的相干作用有关。此外,对于钢板这类表面接近刚性的水下结构而言,镜向散射强度普遍强于前向散射。这表明,上述宽频域混合计算模型是可行的和可靠的,求解频域宽度和精度均得到有效改善,这对水下目标散射强度估计和自由场材料声学测试与评估等领域具有重要意义。

According to enlarge frequency domain effectively, a Broadband Hybrid Calculating Model （BHCM） calculating acoustic scattered field originated from underwater flat object was put forward in detail based on Integral Equation Method and Geometrical Theory of Diffraction （including Uniform Geometrical Theory of Diffraction）, which contained total work frequency range of underwater acoustics. Taking example for rectangular steel panel, numerical calculating and analyzing its underwater acoustic scattered field distribution in the frequency domain was carried out respectively on the condition of different acoustic incident angle. Two important conclusions were attained as follows： The results of two methods all complemented each other in the frequency domain, which were agreed well with one another in the mid-frequency range; and interrelated frequency value was dependent on the geometrical configuration of emitting source, receiving position and structure etc.. Acoustic scattered field distribution with frequency was dependent entirely on the interference effect between various wave components. Moreover, mirror scatter intensity was generally stronger than forward scatter for underwater structure with approximately rigid surface such as steel panel. It was shown that the before-mentioned BHCM was feasible and effective. Calculating precision and frequency width were improved effectively. These conclusions played a very important part in the scatter intensity estimation of the underwater structure target and free-field measurement and evaluation for acoustic material etc.