4.5 Simulation of Maneuvering Motion

　

 With the hydrodynamic coefficients obtained from HPMM tests, computer simulations of the standard maneuvers have been made for 9000TEU container ship.

　

　

 At first, simulations were performed at the model propulsion point to compare the results directly with the data of free running tests.

　

 Fig. 9 shows the results of simulation for 35°starboard turning compared with free running data at full load condition. The simulation predicts a little higher turning rate than free running data at the initial turning stage but the difference reduces as turning develops and reaches to steady state. Thus, simulated advance is shorter than free running data but simulated tactical diameter is almost same with the free running data. Simulation shows smaller speed drop and larger heel angle on the whole. Although the simulation shows reasonable prediction for the free running data, further examination is necessary to find out the reason of discrepancy between simulation and free running data. What is suspected at present is on the modeling of rudder effectiveness at large rudder angle. Unlike a full scale rudder, a model scale rudder mostly experiences a stall at large rudder angle which leads to the reduction of rudder effectiveness. The simulation in this study, however, did not consider this since it is ambiguous yet about stall phenomenon.

　

 Fig. 10 and Fig. 11 show the results of simulation for 20°/20°zig-zag maneuver and 10°/10°zig-zag maneuver compared with free running data at full load condition. They show good agreements on the whole except that the simulated overshoot angles are smaller than free running data for 10°/10° zig-zag maneuver.

　

 Similar comparisons of simulation and free running data are also made at the ballast condition. The comparison of 35° port turning and 20°/20°Zig-Zag maneuver between simulation and free running data are shown in Fig. 12 and Fig. 13 respectively. Here, as same for full load condition, simulation predicts higher yaw velocity than free running data for turning maneuver. In case of zig-zag maneuver, they show good agreements relatively. Simulated roll angles are smaller than free running data but both are quite small compared with the roll angles at full load due to high GM.