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Frigate roll and yaw motions in a steep sea state 6 stern quartering sea (45 degrees off the stern) at an 18 knots ship speed. Left:Yaw. Right: Roll


were Damen Shipyards, Defence Science Technology Group (DST Group) Australia, Defence Materiel Organisation Netherlands (DMO), Delft University of Technology and MARIN. Due to the body-exact approach no separate slamming method is required and impulsive wave loads are readily available. PanShipNL developments in the FAST3 JIP also aimed to advance and validate simulation methods capable of dealing with dynamic stability of ships sailing in severe sea states from astern directions. In that case, the hydrodynamic problem is a combination of resistance, propulsion, seakeeping and manoeuvring. Although CFD methods are in principle suited for dealing with such a multi-disciplinary problem, they are not yet sufficiently efficient for long duration time simulations. Hybrid methods such as PanShip and PanShipNL are more suited to this.


In PanShip and PanShipNL it is assumed that horizontal plane forces can be determined through the use of the transient Green functions, i.e. compute exact forward speed effects on hydrodynamic coefficients. The ship hull is then treated as a low aspect ratio lifting surface and there is no need to include a separate manoeuvring method. In FAST3, PanShip and PanShipNL have been validated for the prediction of calm water resistance, manoeuvring, motions and loads in waves and dynamic stability in stern quartering seas. Two cases are shown here. The first case concerns the mid-ship bending moment on a frigate sailing in upper sea state 5 head seas at 35 knots. The plot shows a comparison between experimental and predicted bending moments by means of PanShip and PanShipNL. The PanShipNL method provides a better prediction of the


negative peak values than PanShip. The second validation case concerns the frigate roll and yaw motions in a steep sea state 6 stern quartering sea at an 18 knots ship speed. The plots show the time traces from the model test and the PanShip and PanShipNL results. For moderate roll motions there is not much difference between the three time traces. However, at the end of the test run when the model showed a broach-like behaviour, the non-linear PanShipNL version captures the increase in roll better. The same is true for the yaw motion.


New SLAP JIP Further validation and development work on PanShipNL will start in the Slamming Load Analysis and Prediction (SLAP) JIP. You are welcome to join this collaborative project.


report 13


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