Some Experiments on Effect of a Propeller on Rudder Forces in Shallow Water

In order to provide basic data needed to predict maneuvering motions in shallow water, the author carried out some experiments concerning propeller-rudder interaction in water of finite depth. The tests were conducted by utilizing propeller-rudder system with the absence of the ship body. Normal forces on a rudder were measured by changing drift angle, propeller loading and water depth. Adopting the so-called MMG Mathematical Model describing maneuvering motions, a theoretical calculation of rudder normal forces in shallow water is made. The shallow water effect is evaluated through infinite images which are arranged below the fluid bottom and above the free surface. Calculated values of the rudder forces agree fiarly well with the experimental results, when the rudder is set in open water. On the other hand, regarding the rudder behind propeller, both agree qualitatively. Additionally, coefficients of flow-straightening caused by the propeller are obtained from measured results of the rudder forces in oblique flows. As a result, it is found that the water depth has a considerable influence on the flow-straightening effect. The values of the coefficient will increase as the depth of water decreases.rights: 社団法人日本船舶海洋工学会協会rights: 本文データは学協会の許諾に基づきCiNiiから複製したものであるrelation: IsVersionOf:http://ci.nii.ac.jp/naid/110003872031