规则波浪中舰船纯稳性丧失计算研究

Pure loss of stability calculation of naval ship in regular waves

[目的]波浪中纯稳性丧失是第二代舰船完整稳性中稳性薄弱性的衡准之一。针对波浪中大倾斜角稳性计算发散问题,[方法]以静水面坐标系为基准,定义了广义纵倾角和广义吃水变量,推导出物理含义清晰的波面方程。在Froude-Krylov假定条件下,结合AutoCAD二维图形面域计算技术和VBA编程方法,提出了规则波浪中舰船纯稳性丧失的计算方法。针对一艘具有阶梯式甲板的舰船,计算了规则波浪中舰船复原力臂曲线,证明大横倾状态具有一致收敛性。[结果]计算得到了规则波浪中稳性变化规律:纵向波浪中,波面高于甲板或低于船底导致有效水线面消失是稳性降低的主要原因;斜浪和正横浪中,波面相对船体横剖面倾斜引起的不对称性,是稳性大幅度降低的主要原因。[结论]计算收敛一致性表明,基于广义纵倾角定义的计算方法可成为评估舰船波浪中纯稳性丧失的有效手段。

The pure loss of stability of a ship is one of the failure modes of the second-generation intact stability criteria. Based on the static surface coordinate system, the generalized pitch angle and draught variable are defined, and a wave equation with clear physical meaning is deduced. Based on the Froude-Krylov hypothesis, combined with AutoCAD 2D surface area computing technology and the VBA programming method, a calculation method of the loss of pure stability of ships in regular waves is proposed. For a naval ship, the righting arm is calculated in regular waves, and the large heel ship state is shown to have an identical convergence. The results of the calculations show that a significant reduction in the meta centric height of the maximum righting arm occurs not just in a wave crest but also in a trough. By analyzing the wave profile under the hull, it can clearly be seen that wave amplitude above the deck or below the bottom of the hull causes the pure loss of stability, and in oblique waves or beam seas, the pure loss of stability is caused the asymmetry of the wave profile on the hull. The coinciding convergence of the calculations shows that the process of the definition of generalized pitch can be employed to assess the pure loss of stability of naval ships in regular waves.