Hydroelastic analysis of floating structures under wave loads

Accurate prediction of hydroelastic response in ocean waves is of great significance to the structural design and reliability design of floating structures. In this paper, based on the potential flow theory, a large floating structure is simplified as a thin-plate material, and the hydrodynamic characteristics of the structure are calculated by using the modal expansion method and the boundary element method. The correctness of the theory and calculation is verified by comparing the experimental and numerical results. Further, the wave properties and structural materials characterization were changed, this paper calculates the stress and deflection of the structure under wave action, and analyzes the effects of hydroelastic response on the safety of the structure.

Investigation of damping effects on low-frequency steady-state acoustical behaviour of coupled spaces

In the low-frequency range, the acoustical behaviour of enclosed spaces is strongly influenced by excited acoustic modes resulting in a spatial irregularity of a steady-state sound field. In the paper, this problem has been examined theoretically and numerically for a system of coupled spaces with complex-valued conditions on boundary surfaces. Using a modal expansion method, an analytic formula for Green’s function was derived allowing to predict the interior sound field for a pure-tone excitation. To quantify the spatial irregularity of steady-state sound field, the parameter referred to as the mean spatial deviation was introduced. A numerical simulation was carried out for the system consisting of two coupled rectangular subspaces. Eigenfunctions and eigenfrequencies for this system were determined using the high-accuracy eigenvalue solver. As was evidenced by computational data, for small sound damping on absorptive walls the mean spatial deviation peaks at frequencies corresponding to eigenfrequencies of strongly localized modes. However, if the sound damping is much higher, the main cause of spatial irregularity of the interior sound field is the appearance of sharp valleys in a spatial distribution of a sound pressure level.

Nonlinear Response of an Inextensible, Free–Free Beam Subjected to a Nonconservative Follower Force

A free–free beam with a compressive follower force applied to one end exhibits interesting flutter and limit cycle oscillation (LCO) responses. Here, the derivation from Lagrange's equations is given for the nonlinear inextensible beam with such a force applied. The inextensibility constraint is met with a Lagrange multiplier added to the Lagrangian, and the beam allowed three rigid body modes in planar motion in addition to its elastic deformation. The Rayleigh–Ritz modal expansion method and the Runge–Kutta method are used to calculate time histories of the forced beam response. This new model is validated against classical results for the stability boundary and new LCO bifurcation diagrams are computed.