Theoretical predictions of steady-state hydrodynamic characteristics of a high-speed vessel with transom stern

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Description/Abstract

Two alternative numerical approaches assessing and modelling the influence of the transom stern on the steady flow characteristics of high-speed vessels are investigated. In the first method the hollow cavity region behind the dry transom is filled with an artificial fluid and the (artificial) flow through the transom stern adjusted iteratively until
atmospheric pressure is reached on the surface of the transom stern, as the physical problem requires. In the second method the surface of the hollow cavity region behind the dry transom is replaced by a flexible appendage.

The initial shape of this appendage is set by a mathematical form, but the final shape of the appendage is determined by means of an iterative numerical scheme of study. Within each iterative step, the fluid velocity and pressure distribution on the appendage are calculated. A finite element model is then used to determine the ‘deformation’ of the appendage due to the fluid pressure, which is used for the next iterative step. The iteration is concluded when the atmospheric and kinematic conditions are satisfied on the modified flexible appendage, thus ensuring it represents the form of the hollow cavity behind the transom stern. A NPL hull form is employed to provide a measure of validation of the present approaches. It is shown that whilst either method may be suitable for predicting the wave making resistance of highspeed craft, the second method provides more accurate predictions of pressure on the hull surface in close proximity to the transom stern.