Application of 3D-CFD modelling for dynamic behaviour of ship in waves

Abstract

Modern seakeeping computations are carried out using a variety of techniques ranging from two-dimensional (2-D) strip theory employing potential flow to three-dimensional (3-D) computations using fully nonlinear unsteady RANS (Reynolds-averaged Navier-Stokes equations) codes. The ever increasing size of ships and offshore platforms has resulted in ‘softer’ hull which require hydroelastic effects to be taken into account when predicting fluid-structure interactions. Majority of such investigations are carried out numerically using potential flow solvers. Although nonlinear potential flow methods are also used, RANS/CFD can fully take into account the nonlinearities and viscous effects. It is important, therefore, to verify and validate the predictions from such numerical predictions.

This thesis aims to investigate the symmetric motions and responses of flexible floating bodies by coupling RANS/CFD and Finite Element software. The two-way interaction between a fluid solver, Star-CCM+, and a structural solver, Abaqus, is applied by exchanging pressures and nodal displacements more than once every time step, namely implicit scheme. A combination of overset and mesh morphing approaches and finite volume solution to allow for the motions of a body at the free surface is used. The air-water interface is captured using a VOF method and improved using HRIC scheme.

The proposed method is applied for a validation case for a flexible barge and a containership in regular head waves for a range of wave frequencies and wave heights. The computational results are compared with experimental measurements and 2-D linear hydroelastic predictions. It is shown that the numerical predictions of flexible bodies can be carried out using the present two-way coupling method. The nonlinearities in wave loads arising from severe flare impact and green water (containership) are well predicted, which also provides some initial insights into the nature of 2-node flexible component.

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Identifiers

ORCID for Pandeli Temarel: orcid.org/0000-0003-2921-1242

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