自由液面效應對潛艇阻力性能影響研究

Abstract

本研究使用商業軟體ANSYS Fluent以計算流體力學方法計算潛艇在淺水域時，阻力性能受到自由液面效應的影響。本研究使用暫態流體計算方法，並使用VOF模型與紊流模型以得到流場資訊。本研究以SUBOFF裸船潛艇為研究對象，船體不含帆罩及穩定翼。 自由液面效應的影響可以分成兩個部分: 考慮入射波浪與不考慮入射波浪。而有關波浪之模擬計算，考慮入射波的模擬將以不考慮入射波的計算結果作為初值，以減少模擬計算時間。 本論文的研究內容包含潛艇下潛深度對阻力之影響，模擬計算之水深由1.1倍船寬變化到3.3倍船寬。研究結果顯示當深度越深，潛艇受到自由液面擾動的影響越小。另在不考慮入射波的情況下， 當航深等於1.1倍船寬時，興波阻力約為總阻力的一半；而於3.3倍船寬深度時，興波阻力則約為總阻力4%。入射波浪對於潛艇平均阻力並無顯著影響，但會產生週期性的阻力振盪，造成的阻力振盪幅度與平均總阻力的比值，也隨著沒水深度增加而降低。 屏除深度因素，振盪幅度也會因入射波條件而異，在本研究中已針對入射波的波長與波高對船體阻力之影響進行研究，並做比較與探討。結果顯示在固定波高的情況下，當波長在0.5倍船長到2倍船長之間，阻力振盪的幅度隨著波長變長而增加。而在固定波長的情況下，阻力振盪的幅度隨波高變大而增加，且振盪幅度與波高大小有呈現線性的關係之趨勢。

The commercial software ANSYS Fluent, a computational fluid dynamics (CFD) method, was used to simulate the effect of the free surface on the resistance performance of a shallowly submerged submarine in this study. A transient method was used in the research, while VOF and turbulence models were used to obtain the flow field information. The submarine studied in this study is SUBOFF bare hull without sail and stability fins. The study of free surface effect can be divided into two parts: with and without the considerations of incident water wave. The results of cases without incident waves served as the initial conditions for cases with incident waves in order to reduce computation time. In present research, the depth of the submarine below the free surface varied from 1.1~3.3 times ship width, and the results show that the influence of the free surface on the submarine resistance reduces as the submergence depth increases. While no incident wave is considered, the wave-making resistance is about half of the total resistance in the 1.1 times ship width submergence depth case, and is only 4% of the total resistance in the 3.3 times ship width submergence depth case. The presence of incident waves shows negligible effect on the overall mean resistance of the submarine, but it will cause periodic resistance oscillation, and the ratio of the oscillation amplitude and the mean total resistance decreases as the submergence depth increases. Regardless of the submergence depth, the resistance oscillation amplitude is also affected by incident wave conditions, and research is done on the effect of wavelength and wave height individually. The results show that, for a fixed wave height with wavelength varying from 0.5~2 times ship length, the amplitude of the unsteady resistance oscillation increases as the wavelength increases. In cases of a fixed wavelength with various wave heights, the amplitude of the resistance oscillation increases as the wave height increases, and the amplitude has a linear proportion to incident wave height.