Transom-stern flow for high-speed craft

Abstract

Two series of experiments have been conducted, one at the University of Michigan (U-M), and one by The University of New South Wales (UNSW), with a focus to characterize the flow in the transom region of a high-speed vessel. At U-M, we have tested a destroyer type model, with and without a stern flap, while measuring pressures in the aft region of the hull and on the flap. The model was tested in both the free-to-sinkand-trim condition and the fixed condition. At UNSW, a series of geosimilar models was tested while measuring the free-surface elevation behind the vessel. The non-dimensional free-surface elevation was found to be primarily a function of the calm-water-transom-draft Froude number. To this end, an empirical formula that estimates the unwetting of the transom has been developed. This formula can be employed in a resistance prediction computer program which will provide an accurate calculation of the hydrostatic force on the transom. As a consequence, the total resistance of the vessel can now be computed accurately, even in the low-Froude-number region.