Study On Exterior Acoustic Of Ships Based On The Cell-based Smoothed Point Interpolation Method

The radiated and scattered noise would have an important impact on the performance of the detection equipment,the comfort of the cabin and the concealment of ships and warships.The research of ship radiated and scattered noise can provide support for optimizing design of structures and enhancing ship's stealth.Numerical simulation has become an effective way of ship noise analysis in recent years,in which the finite element method(FEM)and boundary element method(BEM)are the main methods.But,the boundary element method has low calculation efficiency,and the finite element method has the problems of excessive rigidity of the model and low calculation accuracy of low-order elements.Cell-based smoothed point interpolation method(CS-PIM),as a new type of numerical calculation method,uses gradient smoothing technology to soften the model stiffness on the basis of low-order linear elements,which can effectively improve the calculation accuracy.In this paper,based on a newly proposed model of CS-PIM,that is,the cell-based smoothed radial point interpolation method(CSRPIM)with virtual points,combined with artificial boundaries to deal with the external field acoustic problems of ships.The background elements are used as the smoothing domain in the CSRPIM with virtual points,which does not need to construct additional smoothing domain.At the same time,virtual nodes are introduced into the center of element and the center of edge / face,combined with gradient smoothing technology and radial basis function,the calculation accuracy is improved significantly.Artificial boundary is a common way to deal with the exterior acoustic problems.In this paper,CSRPIM is combined with DtN boundary and PML boundary,and two kinds of exterior acoustic calculation models are proposed.Through the basic example of radiated noise,it is found that the calculation performance of the combination of CSRPIM and DtN is better than that of the combination of CSRPIM and PML boundary,where the former's accuracy and obtained acoustic pressure distribution are closer to analytical solutions than the latter.In order to verify the superiority of CSRPIM,several radiated noise examples are calculated by using CSRPIM-DtN model.The numerical results show that compared with the traditional finite element method,CSRPIM has higher accuracy,convergence,efficiency and stability at high wave numbers,and lower sensitivity to wave number,which extends the frequency range of the calculation in the frequency response of radiated noise.Moreover,the mesh distortion has no significant influence on the existing numerical model,which makes this method have advantages in dealing with complex shape problems.Finally,the CSRPIM-DtN model is extended to the analysis of acoustic scattering problems.First,the dispersion error which is very important in acoustic calculation is analyzed by regular grid.The results show that the dispersion error of CSRPIM is smaller than that of FEM under the same conditions.Both single target scattering and multi-target scattering of rigid objects are studied.The numerical results show that CSRPIM has high accuracy,convergence and efficiency in dealing with acoustic scattering problems.In addition,CSRPIM can recognize backscattering wave and predict arriving time of backscattering wave when dealing with multi-target scattering problem,which verifies the advantages of this method in dealing with scattering problems.Through a large number of exterior acoustic numerical examples,CSRPIM has higher accuracy and efficiency than the finite element method.The CSRPIM-DtN model has a good effect in dealing with the exterior acoustic problems,and has a broad engineering application prospect.