Yingbin Chai

Application of Smoothed Finite Element Method to Two-Dimensional Exterior Problems of Acoustic Radiation

In this work, the smoothed finite element method using four-node quadrilateral elements (SFEM-Q4) is employed to resolve underwater acoustic radiation problems. The SFEM-Q4 can be regarded as a com...

Edge-Based Smoothed Three-Node Mindlin Plate Element

AbstractThe edge-based smoothed finite element method (ES-FEM) was proposed recently to improve the accuracy of the standard finite element method for solid mechanics. In the present paper, the ES-FEM is incorporated with the three-node Mindlin plate element (MIN3) to give a novel edge-based smoothed MIN3 (ES-MIN3) for plate analysis. The system stiffness matrix is computed by employing the edge-based strain smoothing technique over the edge-based smoothing domain. For the purpose of avoiding the transverse shear-locking, the MIN3 element is performed to calculate the strains in each element. From a series of selected numerical examples, it is found that the present ES-MIN3 possesses highly accurate solutions, and can be competitive with many existing plate elements.

Multipole expansion of acoustical Bessel beams with arbitrary order and location

An exact solution of expansion coefficients for a T-matrix method interacting with acoustic scattering of arbitrary order Bessel beams from an obstacle of arbitrary location is derived analytically. Because of the failure of the addition theorem for spherical harmonics for expansion coefficients of helicoidal Bessel beams, an addition theorem for cylindrical Bessel functions is introduced. Meanwhile, an analytical expression for the integral of products including Bessel and associated Legendre functions is applied to eliminate the integration over the polar angle. Note that this multipole expansion may also benefit other scattering methods and expansions of incident waves, for instance, partial-wave series solutions.

T-matrix method implementation for acoustic Bessel beam scattering from elastic solids and shells

T-matrix method (TMM) has been demonstrated to be an effective tool for the application of acoustic Bessel beam (ABB) scattering from rigid shapes, owing to the fact that the incident ABBs could be appropriate to expand on the basis of spherical harmonics [Gong et al., J. Sound Vibr. 383, 233-247 (2016)]. In this work, we try to extend the TMM to further calculate ABB scattering from complicated elastic shapes, spheroids/ spheroidal shells for instance. Some numerical techniques are successfully implemented to overcome the instability problem during matrix inversion procedures for nonspherical shapes. Resonance scattering theory and ray theory [Kargl and Marston, J. Acoust. Soc. Am. 88, 1103-1113 (1990)] are employed to explore and interpret several novel properties of scattering from elastic shapes illuminated by ABBs, thus revealing the corresponding mechanism of scattering by ABBs. Furthermore, the present work will perform as a foundation work to extend the applicability of TMM to study acoustic radia...

Vibration and radiation from underwater structure in shallow water

Prediction of vibration and radiation from large underwater structures is one of the most important research contents in engineering. The cylindrical shell structure is most common structure in engineering, and it is the main component of submarine at the same time. Shells with structural similarity have similar properties due to the similarity principle. Free vibration of the simple cylindrical shell in shallow waters with proper structure mesh and flow field gird is firstly carried out with the usage of finite element method (FEM). The comparison between the FEM result, analytical solution and experimental results gets a satisfactory agreement, indicating the accuracy of FEM approach when used in the fluid-structure interaction problem. A stiffened cylindrical shell structure in shallow waters, taking consideration of the surface and bottom of the waters, is also studied. The natural frequency data and radiation results provide assessment of the influences of water depth, free surface and rigid boundary occurring in the fluid-structure interaction process. The acoustic response in infinite water domain is calculated in parallel. The result shows that the impact of surface, bottom and depth in water on the structure vibration response and the acoustic radiation cannot be ignored, which could provide experimental and numerical introduction in underwater vibration and radiation prediction or measurement.