Topology Optimization Design And Acoustics Evaluation Method Of Ship Structure

Vibration and noise level of ship structures is an important aspect to the performance evaluation.With the ship's development trend to large scale,energy saving and environmental protection,Ship comfort requirements are increasingly important,especialy the fact that Code on Noise Levels On-board Ships came into effct on July 1,2014 and China formally approved the accession of the Maritime Labour Convention on 2006.Comfort requirements are mainly concerned with vibration and radiation noise.In this paper,we study the dynamic optimization design of the ship structure and the method of acoustic assessment of radiated noise in catamaran.First of all,from the perspective of structural dynamics of ship grillage structure,combined with the CAE,the application of structural topology and shape optimization design method in vibration and noise reduction of ship is studied,targeting with typical ship grillage.Size and shape optimization are applied in grillage structure of the bottom,with the weight of the structure as objective function and stress as constraint condition;As for deck grillage,to improve the spatial layout of the top of superstructure cabin,raise natural frequency of grillage structure on top and seek for the optimal distribution of material,topology optimization is applied.New structure type which better for the spatial layout of the top of superstructure cabin have been obtain,it shows that the new one make the material distribution more reasonable,increases grillage structure's natural frequency and meets supposed goals.Secondly,we study the high frequency domain underwater radiation noise calculation method and the distribution of noise.This double interference result is an important study content of the interference phenomenon of the acoustical design of catamaran.In this paper,we take partially submerged and total submerged rectangular catamaran as research object.The model consists of two cuboids with stiffeners.Forces act on the inner panels of catamaran.There are three kind of space between the two cuboids(3m?5m and 10m).The statistical energy method(100-10kHz)is used to calculate the various operating conditions,and the results are analyzed.From the perspective of the radiated sound field,the sound field can be divided into three regions: the fluid dynamic near field,the geometry near field and the far field.Near field and far field are related to the distance of the sound source to the test point,the characteristics of the sound source and the wavelength of the radiation acoustic wave,and give reference opinions about near field,far field division.Finally,Takeing a catamaran as an example,the paper evaluates the its acoustic characteristics of the whole frequency domain about underwater radiation noise.Using the boundary element method and statistical energy analysis,the whole ship statistical energy acoustic model and boundary element acoustic model is established and is used to calculate the noise and comprehensive evaluation is completed.