A seakeeping analysis method for an air-lifted vessel

Abstract

A seakeeping analysis in the frequency domain is presented to predict the motion response of an airlifted vessel (ALV) in waves. The ALV is supported by pressurised air in two separate cushion chambers; the pressure variation in the cushions has a significant effect on the motions of the vessel. The adiabatic gas law is used to couple cushion pressure and the free-surface elevation of water inside the chamber. Attention is focused on the waves generated by the pressure, and a method is presented to compute the corresponding free-surface elevation. New numerical schemes are proposed for calculating the threedimensional free-surface elevation for the four wave numbers. Numerical results of the free-surface elevation, escape area, escape volume and motion responses of the ALV are provided. & 2008 Elsevier Ltd. All rights reserved

A novel 2.5D method for solving the mixed boundary value problem of a surface effect ship

“…The first case is to evaluate the radiation wave due to fluctuating air pressure on the interface. The numerical results confirm that the radiation wave from solving the Dirichlet BVP (Doctors, 1976;Xie et al, 2008;Guo et al, 2017) is very different from solving the complete mixed BVP, i.e. the sidehull effects have significant impact on the radiation wave and should not be ignored.…”

“…The mixed BVP (6) is a novel model presented in this work, in which the sidehull effects on the velocity potential due to pressure are firstly considered. In contrast, in previous papers (Xie et al, 2008;Guo et al, 2015) the sidehull effects were ignored. Obviously, Eq.…”

“…(26)~(27), the radiation wave P on the interface due to fluctuating air pressure on the interface of the SES could have an impact on the motion responses, which suggests the importance of accurately predicting it. In many publications, however, the radiation wave P was neglected (Faltinsen, 2005), or approximated by solving the Dirichlet BVP (Doctors, 1976;Xie et al, 2008;Guo et al, 2017). Here we would like to compare the radiation wave P of the PACSCAT by solving the Dirichlet BVP with the one by solving the mixed BVP.…”

“…diffraction and radiation wave of sidehulls, the radiation wave due to fluctuating air pressure by solving the mixed BVP. The former is a simplified model that was utilized in Doctors (1976) and Xie et al (2008), while the latter is a completely new model formed from the motion equations proposed in this work. The results labeled by 'CFD' were obtained from the RANS (Reynolds-averaged Navier-Stokes equations) solver given by Yang et al (2015), in which the bow fingers and stern seal bags of the PACSCAT are modeled as rigid bodies.…”

“…The 3D numerical methods can be utilized to do so, but they still consume a significant amount of computational resources. For the sake of simplicity, in some works (Doctors, 1976;Xie et al, 2008) the mixed BVP was simplified to a Dirichlet BVP, i.e. the homogeneous Neumann BC as well as the coupling between the fluctuating air pressure and sidehulls was neglected.…”