Tasai Method And Program Development For Fluid Dynamic Coefficient Calculation Of Ships

The ship motion excited by the waves is the important physical phenomenon. It is necessary to calculate the add water mass, add rotation inertia moment and damping coefficients in order to get the ship's motion of six freedom degree. The Lewis form and the Tasai strip theory are adopted to solve the add roll inertia moment, the add mass of sway and heave as well as wave damping coefficients. The calculation program for the add fluid dynamics coefficients of three freedom degrees is developed.The paper reviewed the study history in the ship motion, especially the development history and achievements in the strip theory since the metaphase last century. The strip theory of Tasai is summarized and the detailed calculation formulas are deduced for solving the radiation fluid dynamics coefficients of roll, sway and heave.The program for solving the radiation fluid dynamics coefficients is worked out by using computer language FORTRAN77 considering the ship motion of three freedom degrees. The program is developed by adopting the idea of model, and its advantages are clear of framwork, and easier to read. The calculation method is chosen considering the solving speed and efficiency. Applying the program into the calculation of some Lewis forms, and inputting the parameters of ship's sections and wave frequencies into the computer, the relation between the radiation fluid dynamics of every freedom degree and the frequencies is calculated. The results in the paper are in agreement with the results from the experiments and other methods, therefore the program developed in the paper is correct and reliable. Finally the radiation fluid dynamics coefficients of Yachts Shi-San-Ling-Reservoir are calculated, and the add fluid mass, add rotation inertia moment and damping coefficients of radiation fluid are given.