Study On Flexural Wave Analysis Method Of Typical Ship Structure Based On Non-reflecting Boundary

Hull structure is generally a three-dimensional space system composed of beams,plates and other components with certain spacing.In engineering,hull structure dynamics is usually studied from the perspective of vibration,but the dynamic response analysis based on vibration theory can not reveal the propagation process of vibration.The vibration response in the actual hull is the manifestation of elastic wave propagation process.The elastic wave is generated from the excitation of marine mechanical equipment.And it will eventually cause the surface vibration of the hull and radiate noise to the outside of the ship after the complex propagation process,such as propagation in the plate frame structure and energy conversion at bulkheads,ribs and other structures.Therefore,the research on the systematic acoustic design method of vibration and noise reduction needs to be carried out from the perspective of wave analysis.But due to the complexity of hull structure,the propagation mechanism of internal elastic wave is still unclear.Paper focuses on the key problems in the analysis of wave characteristics in complex hull structures,and analyzes how to set appropriate boundary conditions in finite structure in order to achieve the effect of wave energy is consumed at the boundary without reflection.The transmission characteristics of flexural wave in complex structures is analyzed.Paper mainly carries out research through the following aspects:Firstly,paper introduces the analytical solution of flexural wave in beam and plate structure based on spectral analysis method,and obtains the corresponding theoretical calculation formula of non-reflective boundary through the analysis of end boundary conditions.Based on this,the method of applying the non-reflective boundary to absorb the reflected wave at the boundary of finite scale structure is proposed.For the case that the non-reflective boundary of the plate model derived from the plane wave assumption does not match the diffusion attenuation of flexural wave in the plate,the boundary coefficients are calculated by the method of formula fitting correction of space damping.These methods are the theoretical basis for numerical calculation in this paper.Secondly,based on the theoretical calculation results of non-reflective boundary,the numerical simulation calculation of beam and plate model is carried out.Through the comparative analysis of waveform in the structure under non-reflective boundary and remote boundary,and the error results under different schemes are compared with the analytical results to verify the effectiveness of the proposed non-reflective boundary.Finally,based on the application method of non-reflective boundary of beam and plate structure,the numerical calculation verification of non-reflective boundary of typical plate frame structure of ship is carried out.And the flexural wave transmission characteristics of single stiffened plate,periodic unidirectional stiffened plate frame,cross stiffened plate frame and deck plate frame model intercepted from a certain type of ship are analyzed in turn.The formation mechanism of local resonance band gap of artificial periodic stiffened plate frame structure is briefly analyzed.