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.

Keywords:

• Fast ships
• transom flow
• wave wake
• surface pressures
• transom wetting

Additional information

Notes on contributors

Kevin J Maki

Kevin is a Research Fellow and Adjunct Lecturer at the University of Michigan. He earned his Doctorate from the University of Michigan in the department of Naval Architecture and Marine Engineering. His research interests include numerical and experimental ship hydrodynamics.

Lawrence J Doctors

Lawrence Doctors is a Visiting Professor at The University of New South Wales (UNSW). He is a member of The Society of Naval Architects and Marine Engineers, and a fellow of The Royal Institution of Naval Architects. During his career, most of Professor Doctors’ research efforts have been devoted to numerical ship hydrodynamics, where his interests are centred on the study of advanced marine vehicles. These include catamarans, hovercraft, surface-effect ships and hydrofoil boats. He has published over one hundred and eighty research papers and reports on these subjects.

Robert F Beck

Robert is presently the Herbert C Sadler Collegiate Professor of Naval Architecture and Marine Engineering at the University of Michigan. He is a Fellow of the Society of Naval Architects and Marine Engineers and is the Editor-in-Chief of the Journal of Ship Research. His research interests include all aspects of marine hydrodynamics. Most recently, he has been working on predicting nonlinear motion responses of ships and advanced marine craft to a seaway.

Armin W Troesch

Armin is currently a Professor and Chair of the Department of Naval Architecture and Marine Engineering. He is a Fellow of the Society of Naval Architects and Marine Engineers and holds a professional engineer’s license with the State of Michigan. Since 1969, he has held various engineering, teaching, and research positions including Design Engineer at the Electric Boat Division of General Dynamics, Visiting Research Associate at the DTNSWC Bethesda, MD, and Director of the University of Michigan Marine Hydrodynamics Laboratory. His research interests have expanded over the years from initial work in slender body diffraction forces, hydroelastic springing, and wave energy devices to now include nonlinear dynamics, high speed planing hulls, extreme vessel motions and loads, oscillatory, time dependent real flows, and stern flap hydrodynamics/design.