Numerical Simulation for the Motion Response of an Offshore Ahts Ship in Regular and Irregular Waves

Abstract

This study aims at predicting the hydrodynamic response of an offshore AHTS vessel in regular and irregular waves. The study focuses on predicting the six degrees of freedom responses for ship in the operation condition when ship speed is equal to zero, at various heading angles (0, 45, 90, 135, 180, 225, 270, and 315˚) and for several wave frequencies (0.02~2.0 rad/s). The numerical simulation is carried out using the 3D diffraction/radiation Hydrostar software that is based on potential theory to predict the wave-body interactions. All the hydrostatics, loading and sailing aspects are initially estimated, and then introduced as an input in the simulation process corresponding to the ship speed and heading directions. For the irregular sea simulations, the ITTC spectrum is used to describe the wave for a generic case study in the Black Sea in order to make the study feasible for offshore applications in operational conditions. Further investigations are made using the ISIS_CFD viscous flow solver of the FINETM/Marine software (only for regular waves) to compare the obtained results. The results are presented for the ship response with a considered accuracy based on the previous validations performed by the authors for similar ships.

Numerical simulation for predicting the respose of an offshore heavy lift barge in regular and irregular waves

“…And finally, λ z is the average wavelength. These parameters can be obtained from the ITTC spectrum based on the following formulas [2]: The response spectrum for only the maximum significant wave height is plotted in Fig. 5.…”

“…This study proposes the use of the simplest model of heavy lift vessel, being in the form of an almost box-shaped barge as an initial study for a further investigation that will be carried out by the authors soon, following a series of investigations that were carried out for the offshore oriented ship types, such as the Anchor Handling Tug Supply (AHTS) and the Offshore Supply Vessel (OSV) [1,2].…”