Choosing the safest wave

Sanne van Essen, MARIN, and Herman Peters, Rijkswaterstaat, Netherlands investigate the wind and wave design conditions to study the minimum power ships need to safely and efficiently navigate the southern North Sea.

New energy efficiency rules like EEDI are driving a reduction in the installed power of vessels, but this should not come at the expense of safety and operability in waves. This was recognised by the IMO [6], but small ships (less than 20,000dwt) frequently operating in Dutch waters are exempt from these interim guidelines. Therefore, the Dutch government cooperated with MARIN, as well as Dutch shipowners, builders and designers, to evaluate the minimum power requirements for a typical small ship sailing in waves in the southern part of the North Sea (SNS). The total resistance of a vessel at a certain speed consists of calm water resistance and added resistance due to wind and waves. Given that the wind and wave drift forces can significantly increase the total resistance, the choice of environmental conditions at the start of such a study is critical. This article evaluates the influence of commonlyapplied
environmental assumptions on drift forces experienced by a typical vessel sailing in the SNS.