Wave Drift Forces in Directional Seas in Shallow Water

Wave drift forces in shallow water are dominated by low frequency bound wave effects. The effect of short-crestedness of the waves on the wave drift forces is investigated based on direct evaluation of the near field pressure equations in irregular directional seas. The background to the method is treated and examples of results showing some of the details of the computational method are given. Some trends found for the effect of the short-crestedness on the second order wave drift forces on a typical LNG carrier moored in shallow water are presented. Finally, results are given of low-frequency horizontal motions of the LNG carrier in directionally spread head, bow-quartering and beam seas for a range of directional spreading values.