Further wind tunnel tests on the influence of propeller loading on ship rudder performance

Abstract

An experimental investigation has been carried out into the geometrical and flow parameters which control the interaction between a ship rudder and propeller. The tests used the 3.5m x 2.5m low speed wind tunnel at the University of Southampton. This report presents further results for a series of rectangular all-movable rudders of varying span and chord but with a constant NACA0020 profile. A four-bladed, 800mm diameter, adjustable pitch propeller was used. This porpeller 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 studies into the effect of propeller pitch ratio, rudder aspect ratio, position of the rudder stock, coverage of the rudder by the propeller race, lateral and vertical separation of rudder and propeller. 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) coeffient 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.

The results offer an insight into the physics of rudder-propeller interaction. The data presented are suitable for design purposes and will also 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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