Wind tunnel investigation of the influence of propeller loading on ship rudder performance

Abstract

A detailed investigation has been carried out into the interaction between a ship rudder and propeller combination. The tests used the 11' x 8' low speed wind tunnel at the University of Southampton. This report presents results for a series of three all-movable rudders with the same mean chord of 667mm and NACA0020 sections, but with varying aspect ratio and taper ratio. A four-bladed, 800mm diameter, adjustable pitch propeller was used. This propeller is a modified version of the Wageningen B4.40 series. Open-water results for the modified design were validated against published data.

The test consisted of a series of parametric studies into the effect of the longitudinal distance between the propeller and rudder, propeller thrust loading, rudder aspect ratio, and rudder taper ratio. A five-component strain-gauge dynamometer was used to measure lift, drag and three moments on the rudder and a rotating strain gauge dynamometer the developed thrust and torque of the propeller. In addition, both spanwise and chordwise pressure distributions were measured on the rudder surface. Propeller revolutions were varied between 0 and 3,000 rpm and tunnel wind speeds up to 20m/s were used.

Results are presented in the form of non-dimensional coefficients of lift (C subscript L), drag (C subscript D), spanwise (CP subscript S) and chordwise (CP subscript C) position of the centre of pressure variation with incidence for the rudder. The influence of rudder on propeller performance is given in terms of non-dimensional thrust (K subscript T) and torque (K subscript Q) coefficient variation with advance ratio (J). The surface pressure measurements on the rudder are presented as both a spanwise distribution of the local lift coefficient (C subscript L) and as a surface pressure distribution.

Principal findings of the work were that: increasing propeller thrust loading increased rudder sideforce while delaying stall. For constant rpm the presence of the rudder alters the propellers developed thrust and torque characteristic. Changes in the longitudinal separation of the rudder and propeller had only a minimal effect on the sideforce characteristics of the rudder. The information presented should be of considerable use in numerically modelling the flow interaction and in the development of more advanced ship manoeuvring simulations.

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ORCID for S.R. Turnock: orcid.org/0000-0001-6288-0400

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