Study On Acoustic Radiation Performance Of Foam-filled Annular Rib Sandwich Cylindrical Shell

The sandwich cylindrical shell has the characteristics of high rigidity and good stability.It is a common structural type of many important equipment and is widely used in aviation,aerospace,ships,deep-sea equipment and other fields.Since the self-noise of aircraft,submersibles and other equipment during operation and the noise generated by friction with the surrounding fluid medium directly affect their concealment and operational reliability,the acoustic stealth performance of the cylindrical shell should be paid special attention to.In this paper,the foam-filled ring-rib sandwich cylindrical shell structure is taken as the research object,and the sound radiation performance of the foam-filled ring-rib sandwich cylindrical shell in the free state in the mid-low frequency range from 1 Hz to 1000 Hz is studied.The influence of different shell structures,shell materials,foam materials and foam filling methods on its sound radiation provides a useful reference for the acoustic design of related structures.The main research work and achievements of this paper are as follows:(1)The finite element model of the annular rib sandwich cylindrical shell is established,and its acoustic radiation characteristics are simulated and analyzed.The correctness of the establishment of the finite element model and the accuracy of the calculation method are verified through the comparative analysis with the experimental data in the literature.On this basis,the acoustic radiation performance of annular rib sandwich cylindrical shell,foam sandwich cylindrical shell and foam-filled annular rib sandwich cylindrical shell are compared and analyzed.The results show that in the frequency range of 1 Hz-1000 Hz,the acoustic radiation performance of the foam-filled annular rib sandwich cylindrical shell is the best,which is further 13.52 d B and 10.16 d B lower than that of the annular rib sandwich cylindrical shell and the foam sandwich cylindrical shell,respectively.(2)The effects of shell structure and material on the acoustic radiation performance of foam-filled annular rib sandwich cylindrical shells at medium and low frequencies are studied.The influence of shell,annular rib and other factors on the sound radiation performance of the structure is simulated and analyzed.The results show that the increase of the shell density makes the radiated sound power of the structure decrease first and then increase,while the increase of the elastic modulus has the opposite effect.At the same time,when the inner shell increases by 1 mm,the radiated sound power of the structure decreases on average by 0.92 d B and 0.16 d B.When the total thickness of the inner shell remains unchanged,the increase of the thickness of the outer shell will continue to reduce the radiated sound power of the structure.In addition,when the thickness of the ring rib increases by 1 mm,the radiated sound power can be reduced by 0.74 d B on average,and the number of 6 ribs can be reduced by 0.25 d B on average.Constraining the ends of the structure and placing it in water enhances the acoustic radiated noise capability of the shell compared to the free state.(3)The effects of foam materials and filling methods on the acoustic radiation performance of foam-filled annular rib sandwich cylindrical shells at medium and low frequencies were studied.The effects of foam type,acoustic parameters,thickness,location and filling rate on the sound radiation performance of the structure under different filling methods were simulated and analyzed.The results show that the radiated sound power of the structure decreases with the increase of the foam flow resistance and tortuosity factor,and increases with the increase of the porosity,but the change of the characteristic length has no obvious effect on the sound radiation performance of the structure.The radial filling position of the foam has little effect on the sound radiation of the structure,and the effect is slightly better in the middle;the increase of the foam thickness and the filling rate can effectively reduce the sound radiation of the structure,and when the thickness increases by 3 mm and 5 mm,the radiation The sound power is reduced by 1.13 d B and 1.15 d B,respectively.The sound radiation performance of the structure is more sensitive to the filling rate under the centralized filling method.Under the same filling rate,the uniform filling can reduce the radiation noise of the structure more than the concentrated filling.