Research on target strength characteristics of the “orca” extra-large unmanned underwater vehicle

Objectives To enhance the understanding of the target strength (TS) characteristics of extra-large unmanned underwater vehicles (XLUUVs), a systematic analysis is conducted on the TS characteristics of the “Orca” XLUUV in the 1k-10kHz frequency band. Methods The finite element method is employed to calculate the TS of the Orca model in the 1k-2kHz frequency band, while the planar element method is used for the 3k-10kHz band. The results are compared with those of the Benchmark model. The angular detection probability is proposed as a more comprehensive indicator for evaluating the stealth performance of unmanned underwater vehicles (UUVs). A scaled model experiment is conducted in a water tank, and a correction method is proposed for the experimental target strength measurements. Results The TS characteristics of the Orca model have been studied at first. Compared with the Benchmark model, the Orca model exhibits better stealth performance in the azimuthal direction, with additional advantages in the circumferential direction at higher frequencies, which becomes more pronounced as frequency increases. For cases where the distance between the hydrophone and transducer fails to satisfy the far-field condition, a correction method is proposed to the experimental target strength measurements. The corrected target strength shows better agreement with the simulation results, thereby validating the accuracy of the numerical simulations. Conclusions The findings of this study will fill a gap in the TS database for XLUUVs and provide a theoretical basis for optimizing underwater detection systems and the stealth design of UUVs.