岸壁效應對波浪中之船體運動之影響

The Bank Effect on the Motion Behaviors of a Ship Advancing in Waves

本文發展了一套數學模式來預測岸壁效應對船舶在波浪中之運動影響。文中利用了二維截片理論與影像法來解決相關之流體動力問題。相關之流體動力條數如附加質量、阻尼條數與激盪力由於岸壁之出現會受到影響。其處理方式是利用類似雙體船的方式，但偶合項必須額外考慮，文中亦利用四階之朗奇庫塔之方法來解時程領域之模擬。本文考慮了兩種波向以及不同岸壁間距，而為了簡化起見，省略了淺水效應對波浪之影響。本文之結果顯示岸壁有減緩波浪引起之船體運動之效應，尤其在橫向波。本文之結果可以提供未來船舶在靠近碼頭操縱時一些有用參考資訊。 The paper presents a mathematical model to predict the motion behaviors for a ship advancing in waves with the bank effect. The two-dimensional strip theory and the image method are applied to solve the related hydrodynamic problems. The hydrodynamic coefficients of the ship such as the added mass, damping coefficient and exciting forces are affected due to the appearance of the bank and treated by using the image method; however the shallow water effect on the wave is neglected for simplicity. The empirical formulas for steady problem based on the Bernoulli's pressure equation are also derived. The time domain simulation technique is applied to deeply analyze the motions by using the 4th order Runge-Kutta method. Two wave headings are considered with respect to different clearances between the ship and bank. It is interesting to find that the bank effect might relieve the wave induced motions on the ship especially in the beam sea condition. The present results can offer some valuable information for the future studies on the ship maneuvering characteristics approaching a port.