旅客船运行时波浪形态的试验研究英文文献和中文翻译(3)
For normal people at the seats and with belts the number of injured should be low. Table 3: Limits for risk estimation of tests of the “fall” system corresponding to the full-scale boat. Risk level Events connected with risk Low Moderate High Acceleration limits. Co-ordinate axis Y and Z [g] ≤ 7 7-10 ≥10 Max roll angle [deg] ≤ 50 ≥50 - Risk Evaluation for the Chute System In the present study the risks connected with the embar-kation phase of evacuation by the chute system were investigated. This is the phase when the system has already been launched and the passengers should em-bark the raft by first sliding down to the platform and then climb into the life raft. The risks connected with the other phases of the abandon ship process have been left out. In contrast to the lifeboat system, the chute system in the embarkation position is exposed to forces both from the incoming and reflected waves and the motions of the ”mother” ship. The following parameters were taken into account for the risk assessment (see also Table 4): • change of the chute length; • maximum roll angle of the boarding platform and the life rafts; • deformation of the chute form (e.g. the chute can be jammed between the platform and the mother ship). Table 4: Limits for evaluation of tests for the chute. For an inpidual passenger during embarkation these events can result in falling into the water and injuries, such as breaking legs and arms. The risk estimation at each test is based on video re-cordings and measurements of the chute length. Simi-larly as the risk evaluation of evacuation by the lifeboat the low risk corresponds to an estimated probability of injuries of about 0.5%, the moderate about 5% and the high about 50% for an arbitrary person. Results The results of the tests of the evacuation equipment are presented in this section by using the estimation of risks as described above. The results from the wave meas-urements are also presented. Results from the Wave Measurements In this paper the wave climate was examined for three scenarios, namely the cases when the ship was soft-moored, was able to drift and had an additional drift force in order to resemble the additional drift velocity a full-scale ship experiences due to wind. The amplitudes of the resulting wave system next to a ship exposed to beam seas as well as the relative ampli-tudes between the wave and the ship hull has been pre-sented for the three scenarios by Ekman (2004). It was concluded that there were no significant differences in amplitudes between the three cases soft-moored, drift and extra drift. However, the appearance of the wave i.e. the smoothness of the waves was not examined. Therefore, in this paper the measurements are further discussed and an investigation of the wave smoothness and possible shifts in frequencies are examined using Fourier analysis. When examining the measurements from the wave tests it can be noted that the wave climate is different on the windward and leeward sides. The resulting wave on the windward side consists of a propagating wave for longer incident waves, but resembles a standing wave for shorter waves, i.e. for waves with angular frequencies higher than 0.8 rad/s (corresponding to a wavelength approximately three times the ships breadth). On the leeward side however, the wave system always is a propagating wave. The absolute amplitudes for these waves vary with the incident wavelength. For long waves the resulting wave amplitudes on the windward side are in the range of 1-1.5 times the incident wave amplitude while approach-ing three times the incident wave for short waves. Since a wave reflected against a wall would produce an ampli-tude twice as high as the incident wave the results indi-cate that the diffracted waves due to the ships presence and the radiating waves due to the ship motions coin-cide and produce waves higher than for a perfect re-flected wave. On the leeward side the amplitudes are the same as the incident amplitude for long waves and ap-proach zero for shorter waves. For details see Ekman (2004). Even though the amplitudes approach zero for shorter waves (high angular velocity) on the leeward side the relative amplitude between the wave and the hull are not zero due to the motion of the ship, see Fig. 6 (Ekman 2004). In this figure the measurements are pided with the incident wave amplitude, thus providing non-dimensional data. The figure also shows that the relative amplitudes are higher on the windward side than on the leeward side except for waves with low angular velocity (long waves). It can also be seen that the relative ampli-tudes are lower fore and aft compared to amidships.