A description is given of an investigation into the flow straightening effects on a ship rudder of an upstram propeller and hull. In order to quantify these effects an experimental investigation was carried out using a 3.5 m x 2.5 m wind tunnel. The tests were carried out with an all-movable rudder and a representative propeller for drift angles up to ±15°.
Three different lengths of centreboards were tested upstream of the rudder-propeller combination, together with a representative hull. Flow straightening effects were found to be dependent on the type of upstream body, drift angle and propeller thrust loading. The effects of the three centreboards upstream of the propeller were found to be significantly greater than the effect of the propeller on its own. The straightening effects of the hull were found to be less than those for the centreline boards. There was an increase in flow straightening with increase in propeller thrust loading at a drift angle of 15° but at 7.5° drift this effect was less apparent and sometimes reversed.
The overall results provide a better understanding of flow straightening effects and data for improving the prediction of manoeuvring rudder forces. The data for the centreline boards are likely to have applications for vessels with a relatively thin upstream skeg, whilst the data for the rudder plus propeller combination in isolation should be suitable for vessels with open water sterns, such as twin screw vessels.
[1]
D L Gregory,et al.
Propeller Slipstream Performance for Four High-Speed Rudders Under Cavitating Conditions,
,
1974
.
[2]
Stephen R. Turnock,et al.
The effect of the hull on the manoeuvring performance of rudders
,
1998
.
[3]
Masayoshi Hirano.
7. A Practical Calculation Method of Ship Maneuvering Motion at Initial Design Stage
,
1981
.
[4]
A M Kracht.
RUDDER IN THE SLIPSTREAM OF A PROPELLER
,
1989
.
[5]
Anthony F. Molland,et al.
WIND TUNNEL INVESTIGATION OF THE INFLUENCE OF PROPELLER LOADING ON SHIP RUDDER PERFORMANCE
,
1992
.
[6]
Stephen R. Turnock,et al.
Wind tunnel tests on the effect of a ship hull on rudder-propeller performance at different angles of drift
,
1995
.
[7]
Anthony F. Molland,et al.
PERFORMANCE OF AN ENHANCED RUDDER FORCE PREDICTION MODEL IN A SHIP MANOEUVRING SIMULATOR
,
1996
.
[8]
A. F. Molland,et al.
A five-component strain gauge wind tunnel dynamometer
,
1978
.