PanShip developments for fast ship simulation

Frans van Walree


The simulation method PanShip has matured into a versatile tool for the prediction of the seakeeping behaviour of fast ships. This article discusses developments and highlights some of the results of validation work.

Recently, the prediction of impulsive wave loads was added to PanShip in the FAST3 JIP. Additional capabilities include dynamic stability investigations for ships operating in stern quartering seas.

PanShip is a time domain panel method based on the transient free surface Green function to incorporate wave-making effects. Free surface conditions are linearised around the mean free surface, allowing the hydro- dynamic problem to be solved using panels on the ship surface only. PanShip is developed to simulate the motions of high-speed and/ or advanced ships in waves and includes modelling options for propulsion and a wide range of passive and active appendages. Semi-empirical formulations are applied to include viscosity effects.

Two versions There are two versions of PanShip: a semi-linear (PanShip) and a semi-nonlinear version (PanShipNL). The difference lies in the way the hydrodynamic solution is computed. PanShip uses the mean wetted body surface at speed for radiation and diffraction forces, while using the instantaneous wetted body surface for the undisturbed wave forces. This approach is efficient since the most time-consuming part of the computations needs to be performed only once. PanShipNL uses the instantaneous wetted surface for all hydrodynamic forces, resulting in more accurate computations. This latter approach is necessary to compute impulsive wave loads (slamming) but is

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Mid-ship bending moment for a frigate sailing in upper sea state 5 head seas at 35 knots

obviously also less time efficient. To improve efficiency, the PanShip Code has been adapted for running on machines with parallel CPUs.

The capability of dealing with ship motions at a high forward speed is a unique feature of PanShip, and the tool is now increasingly used for high-speed ship projects at MARIN. This is often in tandem with seakeeping model experiments. In typical cases MARIN

uses PanShip to scan a large variety of ship speeds, headings and sea states for possible critical behaviour, before using PanShipNL to study the most critical conditions in more detail. In this way, optimal use is made of the efficiency of the first method and the accuracy of the latter.

FAST3 JIP PanShipNL has been developed in the FAST3 JIP. Participants in this JIP

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