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Abstract
In the design of all marine craft the prediction of a vessel’s resistance characteristics is a major consideration. The
accurate prediction of resistance is particularly important in the design of modern high-speed vessels where the primary
contractual obligation placed upon the builder is the vessel’s achievable speed. Investigation was made of the methods
of Doctors and Day, whereby the traditional Michell wave-resistance theory, published in 1898, is improved on through
a better understanding of the hydrodynamics of transom sterns and the application of statistically determined form
factors.
One of the difficulties with the Michell theory is how to account for the hollow that forms behind a transom stern,
a feature prevalent in high-speed vessels. A common approach in the numerical prediction of wave resistance for
transom-stern vessels is to discretize the hollow as a geometrically-smooth addition to the vessel. Therefore, of great
importance in accurate prediction of wave resistance is the hydrodynamics of, and in particular, the length and depth
of the hollow formed behind the transom stern. Accordingly, a systematic series of transom-stern models were tank
tested at various drafts and speeds in order to determine experimentally the length and depth of the hollow as a
function of vessel speed, draft and beam.
From the experimental data, algorithms for the determination of the length and depth of the transom hollow, have been
developed and utilised in the discretization of the transom hollow for prediction of resistance using the Michell wave-
resistance theory. Application of the developed hollow algorithms produced significant improvements in correlation of
the experimental and theoretical predictions of total resistance, particularly in the lower Froude range.
In addition to the transom-hollow investigation, form factors were obtained using least-squares regression of existing
experimental data. The form factors were based on the major geometric parameters of the models used. In the research
presented here, the method was applied to a large range of published resistance data for high-speed displacement
vessels. Considerable improvement in correlation, between theoretical and experimental predictions of total resistance,
was obtained by incorporating the calculated form-factors into the total resistance formulation.