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gradients in equation (14). Figure 28 shows the drift forces for small forward speed. In contrast with the Diffrac results, small speed has a small effect on the forces. In figure 29 we show the wave drift damping, which can be written as

Our results agree well with measurements.

In figures 30 and 31 respectively the heave and pitch response are shown for Fn= .14, .17 and .20. We compare the measurements with the strip theory calculations. In Figure 32 the drift forces or added resistance for higher speed are given. For the higher frequency strip theory doesn't agree very well with the measurements. Our first results, the small markers, look promising. For the lower frequencies the coarse mesh gives good results, but for the higher frequencies we need the finer mesh. At the presentation we will show more results. We have to make more calculation with the finer mesh, so the numerical differentiations on the hull, especially at the bow, will be more accurate.

4
Conclusions and further research

In this paper we show the extension of our method to higher speed. We have made a promising start. Our extended algorithm turns out to be efficient and reliable for low speed up to Fn=.1. Also the hydrodynamic coefficients for higher speed are calculated. Increasing the speed, we need a very accurate numerical differentiation of the gradient of the potential on the hull to compute the added resistance. After the implementation of a finer mesh we are able to tackle this problem as well. In the future we will also carry out the stability analysis.

Acknowledgements

Financial support for this work and the mesh of the ship-hull are given by the Maritime Research Institute Netherlands.

References

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