3. QUASI-STATIONARY HYDRODYNAMIC FORCES OF TEST RESULTS
This section shows the quasi-stationary hydro-dynamic forces acting on an arc-type ship model (see Table 1), which were analyzed from harmonic captive tests carried out in a towing tank (Length 50m, Width 3.5m, Depth 1.5m) at Hokkaido University. The harmonic captive tests were executed by an x-y carriage mounted on a towing carriage running at constant speed (see Fig. 2). The quasi-stationary hydrodynamic forces that occurred in the harmonic captive test are shown in Fig. 3 as an example of pure-sway motion which shows the behaviors of the quasi-stationary hydrodynamic forces as a component of the measured forces (see Fig. 3). The behaviors of quasi-stationary hydrodynamic forces carrying kinematic variables in PMM tests are translated into another expression against a kinematic variable, e.g. v'=-sinβ,r'=r・Lpp/U instead of time as follows.
Forces in pure-sway motion;
Fig. 4 shows another expression of the quasi-stationary hydrodynamic forces (symbol:・) exerted in a harmonic captive test of pure-sway motion (|β|≦14.5°see Table 2). Fig. 4 also contains the stationary hydrodynamic forces (symbol:○) exerted in a stationary straight-line test of oblique towing motion (β≦90°)  for the comparison and validation of the quasi-stationary hydrodynamic forces. Fig. 4 indicates that the quasi-stationary hydro-dynamic forces of the pure-sway test are in good agreement with the stationary hydrodynamic forces obtained from the oblique towing test.
Fig. 3. Time histories of harmonic pure-sway motion.