| Popis: |
Theoretically and experimentally the author has researched the normal force and the moment of a ship on the turning, and now can calculate them. In this paper the author theoretically deals with the course stability of a ship on the straight course and the steady turning course, and also the steady turning radius. The results are as follows:-(1) The criterion of the course stability is same to the results which have been researched and now it can be calculated in each ship theoretically. It is more stable when trim by stern than even keel condition and main cause is the large decrease of CmGα. (CmGα is the derivative of moment coef. about centre of gravity. CmG and α is the drift angle.)(2) The course stability in the steady turning is always stable if stable in the straight course and the increase of stability is very much. So it can become stabe in the steady turning, even if unstable in the straight course.(3) The turning radius can be calculated by solving the quadratic of ω. (ω=ship length turning radius) Also, Davidson's total less rudder moment can be calculated theoretically and is same to Davidson's experiments qualitatively. |
