以船體動態反應預估船舶遭遇海況之研究

THE PREDICTION OF THE ENCOUNTERED SEA STATE BASED ON THE SHIP DYNAMIC RESPONSES

為了降低船舶與船上人員在惡劣海況下的危險，本研究開發出一套船舶海況監控輔助系統，協助操船者對遭遇海況的了解，並給予最佳操船建議，以利操船者根據此結果適時改變操船方式，提高人員、貨物及船體的安全以及乘客的舒適感。本研究利用波浪造成之船體運動反應及波浪負荷，推估波高、平均週期和主波波向角等波浪參數。以頻率領域船體運動程式模擬船舶在不同船速、波高及平均週期的海況下之全航向船體運動及波浪負荷，透過ITTC能量波譜模型獲得在不規則波下各物理量之有義值（Significant Value），並建立資料庫，作海況推估之需。為了驗證本文方法之可行性，另外使用時程領域船體運動程式，模擬一段時間之船體運動反應和波浪負荷，以此結果逐一與資料庫內各海況下之船體運動反應和波浪負荷相比較，推估出即時的波高、平均週期和主波波向角作測試與驗證。 In the paper, a sea state monitoring system on board is developed to assist the ship operator to understand the encountered sea state. It also provides the optimal operational directions to enhance the safety of the ship. The ship motion responses and wave loads, i.e. heave, pitch, roll, vertical acceleration, vertical shear force and vertical bending moment, are adopted as the parameters to estimate the ship's encountered sea state including the wave height, average period and wave direction. By using the frequency domain technique, we calculate a series of ship motion response and wave loads with respect to different ship speeds, wave heights, average periods and wave directions. Then, based on the significant values through ITTC spectrum, the calculated results are established as the data base to estimate the encountered sea state for the ship. In addition, the time domain technique is also applied to simulate related ship motion response and wave loads in order to verify the validity of the present technique. From the comparisons, we find that the sea state monitoring system developed here can work well and the optimal operation speeds and headings can also be suggested for reference of the ship navigation.