Hydroelasticity of marine vessels advancing in a seaway

Abstract

Hydroelasticity is an important issue in the design of modern-day marine vessels, because of their flexibility associated with lighter construction materials and higher design speeds. The present study extends the hydroelasticity method by including effects of vessel forward speed and utilizes a direct solution approach instead of the modal superposition method, which requires structural details not available in early design stages. The model has two components, describing respectively, the elastic deformation of the vessel and the motion of the fluid. Small amplitude assumptions of the surface waves and vessel deformation lead to linearization of the problem, which is solved in the frequency domain. The formulation adopts a translating coordinate system with the vessel speed. The linear free surface boundary conditions account for the modification of the steady flow around the vessel. The radiation condition for the scattered waves takes into account the Doppler effect due to forward speed. A boundary element model describes the potential flow associated with the current and waves around the vessel. A finite element model relates the structural deformation to the fluid pressure through the kinematic and dynamic boundary conditions on the wetted body surface. This direct coupling of the structural and hydrodynamic systems leads to a system of equations in terms of the body surface oscillation, which includes elastic and rigid-body motions. The model is verified and validated in part with laboratory data on a rigid hull advancing in head seas and with published numerical results from the modal superposition method without vessel forward speed. A parametric analysis of a Wigley hull shows the forward speed introduces new resonance modes that amplify the response and stress of the vessel. The model provides a useful design tool to investigate the effects of vessel elastic deformation and forward speeds on structural performance and seakeeping.