A Method to Analyze Decay Pattern of Near-Field Evanescent Wave in Finite length Cylindrical Shell

An approach is proposed in this paper to analysis the decay characteristic of near field evanescent waves from a finite cylindrical shell. Firstly, the wave-number spectrum method is used to obtain the component of main vibration mode. Then the evanescent wave theory for infinite cylindrical shell is adopted to approximately analyze the decay characteristic of near field evanescent waves from the finite cylindrical shell. Based on the analysis results for evanescent waves, the interface between the near field and far field and the position of artificial boundary of numerical methods can be determined. In the end, comparison of numerical results between the FE-IE method and FE-BE method shows the validation of the approach for analysis the decay characteristic of near field evanescent waves. The proposed method can be used to evaluate the decay characteristic of near field evanescent waves from finite cylindrical shell structures and simple shape of ducts.