The influence of the expression method of aH on the turning motion
In this study, the effect of the analyzing procedures on hydrodynamic derivatives and expression method of interaction force on the estimating maneuvering motion are discussed using proposed experimental results of Esso Osaka. Hydrodynamic forces acting on hull are discussed from viewpoint of experiment range in captive model tests, analyzing procedure and propeller loading. The differences in predicted maneuvering motion due to interaction forces are discussed from viewpoint of estimated flow velocity at propeller and interaction between hull and rudder.
The conclusions in the present investigation are as follows:
1) The experiment range in captive model tests affects the identification for non-linear and coupling derivative. In the initial turning condition, the effect of the experimental range of the captive models test is small. However, the effects of the experimental range of captive model appear at the steady turning motion. Experimental range should be decided depending on non-linearity of hydrodynamic force.
2) In case of Esso Osaka, both analyzing procedure mentioned in this paper shows the difference of identified hydrodynamic derivatives. However, the influence of the analyzing procedure on estimation of maneuvering motion is small.
3) Identified non-linear derivatives may change due to the propeller loading condition. However, the difference of derivatives dose not make a big difference on estimation of turning motion in case of Esso Osaka.
4) Predicted wake fractions at propeller position including maneuvering motion show good agreement with the result of free running test. In case of Esso Osaka, the difference of predicted 1-wP give a small effect on the estimation of turning motion.
5) In case of Esso Osaka, the effect of the prediction of aH on the estimation of turning motion is small. However, there seems to be effective in the estimation of the maneuvering condition in which speed and propeller revolution are changed drastically.
 The Research Committee of Dynamic Performance Maneuvering and Control Section : Prediction of Maneuverability of a Ship, Bulletin of The Society of Naval Architects of Japan, N0.668 (1985)
Atstushi Ishibashi is Lecturer of Tokyo University of Mercantile Marine. His major fields are ship maneuverability and safety evaluation of ship maneuvering.
He holds a Bachelor's degree(Navigation) from Tokyo University of Mercantile Marine, a Master's degree(Navigation) from Tokyo University of Mercantile Marine.