Flexible inflatable structures in underwater acoustics: Scattering experiments

Underwater artificial acoustic structures can be used to simulate the echo characteristics of complex targets, achieving the effects of underwater acoustic deception or interference. This paper extends the morphology of passive underwater acoustic structures to flexible inflatable designs and proposes a series of foldable and deployable flexible structures, replacing rigid reflective surfaces with flexible membranes. Flexible inflatable structures offer advantages such as foldability for storage, ease of inflation and deployment, and lightweight energy efficiency, thereby advancing the engineering applications of artificial structures in underwater acoustic scattering modulation. An underwater constant − depth hovering inflatable device was designed and fabricated to enable the underwater storage of flexible structures and maintain a constant − depth hovering state in water after launch. Acoustic scattering experiments were conducted on cylindrical and plate-like tube bundles, multi-cell corner reflectors, and their topological configurations, which serve as representative flexible inflatable structures. Monostatic echoes were obtained for the flexible inflatable structures, revealing the variations in target strength with respect to frequency and spatial orientation, and the statistical directional characteristics. A combination of flexible inflatable corner reflectors was utilized to simulate the horizontal directional distribution of echo highlights from complex underwater targets. The results show that the acoustic scattering characteristics of flexible structures can be used to simulate the highlight structure of underwater target echoes, achieving a good simulation effect of underwater target echoes. These structures can also be used in the design of underwater acoustic jammers, providing support for the application of underwater acoustic simulators or jammers. More flexible inflatable structures can be explored in the future.