Study On The Acoustic Scattering Characteristics Of Multi-Cabin Cylindrical Shell

With the increase of underwater operation tasks and functional requirements,the development of underwater vehicles is becoming more complicated and diversified,and the detection and identification of underwater vehicles is increasingly urgent.The acoustic scattering characteristics of underwater targets are the basis and premise of underwater target detection and identification.After nearly ten years of rapid development,the target characteristics of various complex structures have been extensively studied,including adding periodic ribs or transverse bulkheads,single and double layers hulls,transverse slabs,acoustic coating,etc.,but the main structure is still a single vacuum cylindrical shell or a double-layer water-filled cylindrical shell between the sides.Rarely,the axial direction of the cylindrical shell is multi-cabin sections filled with different media.The cylindrical shell of the subdivision section is the main structural form of various underwater vehicles.At present,there are few studies on the sound scattering characteristics of partially water-filled cylindrical shell structures.The sound scattering characteristics of the mixed structure of the water-filled and air-filled tank sections have high practical significance for the study of the fine characteristics of the target in the water.In this paper,the multi-cabin cylindrical shell is taken as the research object,and the sound scattering characteristics of the two-segment cylindrical shell filled with air-air,air-water,and water-water are studied respectively.Firstly,various numerical calculation methods used in this paper are introduced,including the fast calculation method of the acoustic scattering of the axisymmetric model under non-axisymmetric excitation based on finite element,the plate element method based on physical acoustics,and the bright point model method based on the integration of the steady phase method.It provides a solid calculation foundation for the numerical study on the research object in this paper.Then,taking a rigid cylindrical shell as an example,the above three numerical methods are compared and verified to ensure the correctness of the numerical calculation in this paper.Furthermore,numerical calculations were carried out on the three types of multi-cabin cylindrical shells filled with air-air,air-water,and water-water.The frequency angle spectra of the acoustic target intensity with frequency and incident azimuth were obtained.The analysis of the broadband acoustic scattering interference fringes reveals the "eight" shaped fringes generated by the geometric echo interference from the cylindrical end face and the bright spots at the interface of the tank section,and the additional waves of the fluid caused by the water-filled tank section.The characteristic mechanism of different liquid-filled structures was analyzed.Finally,sound scattering characteristics experiments of three types of multi-cabin cylindrical shell models were carried out in an anechoic tank.The experimental scheme and data processing method were introduced in detail.The time-domain signal was processed by matched filtering to obtain the distance-angle spectrum.The echo structure and bright spot distribution of the three types of models were analyzed deeply.The characteristics of multi-path propagation of sound waves in the water-filled tank section were also revealed.In frequency domain,the frequency-angle spectra were obtained by frequency-domain transformation of the time-domain signal.The acoustic scattering interference fringes are consistent with the numerical calculation results,and the experimental verification of the acoustic scattering mechanism of three types of multi-cabin cylindrical shells was completed.In summary,the research on the acoustic scattering characteristics of the multi-cabin cylindrical shell provided in this paper provides a certain amount of data support for the target feature library of various underwater vehicles and lays a theoretical foundation for the active sonar detection and recognition of underwater targets.