大型貨櫃船結構動態負荷分析

Dynamic Loadings for Structural Analysis of a Large Container Ship

本文結合三維船舶運動理論與船體有限元素結構直接分析，對一艘大型貨櫃船進行數值計算並研究其在波浪中船舶運動及船體波浪負荷特性。運動及負荷的數值計算包含二維截片法（strip method）及三維小板法（HSC-3D），其中三維小板法包括三維振盪源流（3D pulsating source, 3DP）及三維前進──振盪源流（3D translating-pulsating source, 3DT）兩種不同的三維源流分布模式計算並比較其在波形及流體動壓力之差異。藉由本研究發展之流固界面轉換程式，在靜水面下之浸水部位船殼局部動態壓力負荷可順利轉換至船體結構之有限元素分析模型，以進行船體結構在波浪中的受力反應分析。對於有限元素結構分析模型之水動力負荷與船體運動慣性力合力之差異，已在本文中討論，理論而言，三維前進──震盪（3DT）模式充分考慮船舶前進速度的效應，是較為接近實際物理現象的理論模式。同時，對於不同源流分布模式（3DP, 3DT）計算的負荷對貨櫃船結構分析所造成的船體結構反應差異進行探討。 This paper demonstrates the results on the combination of 3D ship motion and wave loads program (HSC-3D) with finite element strength analysis of ship hull structures. The ship motion responses and wave loads of a large container ship in oblique waves have been calculated and compared by using three computer programs which are based on 2D strip method, 3D pulsating source distribution technique (3DP) and 3D translating-pulsating source distribution technique (3DT) respectively. An interface program has been developed to transfer the hydrodynamic pressures obtained from 3D Green function method to structural finite element model. Based on the linearised theory, this interface program transfers the hydrodynamic pressures on the wetted hull surface to the finite element model and converts to the nodal forces smoothly. The discrepancies between the total resultant hydrodynamic forces and inertia forces for the large container ship in waves have been discussed. Some comparison results and examples of structural analysis based on the hydrodynamic pressures calculated by 3DP and 3DT techniques have been shown and discussed in this study.