针对液舱内自由液面对浮态和稳性的影响，文中提出了一种新的多凸体组合结构浮态算法。该方法将浮体和液舱分解成多个四面体单元，通过分析每个四面体与水面/液面的相对位置关系来确定浮体的浮力和浮心以及液舱液体的重心。该方法还提出了一种改进的双重迭代法用来确定多凸体组合结构的浮态：内层迭代法模拟浮体的升沉运动，得到浮体外的水面方程和液舱内的液面方程；通过外层迭代法模拟浮体的旋转运动。两种迭代方法交替进行，直至浮体的重力作用线和浮力作用线之间的距离满足精度要求，同时重力等于浮力。自编程序对某半潜船和某半潜式海洋平台的多种典型工况进行了浮态计算，同时也考虑了自由液面影响。此外利用Maxsurf建模进行了对比分析，还利用AUTOCAD进行了精度验证。对照结果表明：该研究提出的算法可以考虑自由液面对浮态的影响，原理清晰，收敛性好；算法无论对传统的单凸体结构（例如单体船），还是多凸体结构（例如多体船、漂浮式海洋平台等）均更容易取得准确解，且计算效率更高；算法可以实现“搭积木”式的建模方式，多工况建模时可以极大地减小工作量；算法无需依赖国外第三方图形平台（比如AUTOCAD、CATIA），可为我国相关工业软件的国产化打下良好的基础。

In view of the influence of free surface in tank on floating state and stability, this paper proposed a new floating state algorithm of multi-convex composite structure. The floating body and the liquid tank were decomposed into multiple tetrahedral elements, and then the buoyancy and center of buoyancy of the floating body and the center of gravity of the liquid tank were determined by analyzing the relative position of each tetrahedron and the water surface/liquid surface. An improved double iteration method was also proposed to determine the floating state of multi-convex composite structures: the inner iteration method was used to simulate the heaving motion of the floating body to obtain the water/liquid surface equations outside the floating body and inside the tank; the rotation motion of floating body was simulated by outer iteration. The two iterative methods were carried out alternately until the distance between the gravity action line and the buoyancy action line of the floating body meets the accuracy requirement, and the gravity is equal to the buoyancy force. The study calculated the floating state of a semi-submersible vessel and a semi-submersible offshore platform under various typical working conditions using self-compiled program, and the influence of free surface was also considered. In addition, MAXSURF modeling was used for comparative analysis, and AUTOCAD was used to verify the accuracy. The results show that: (1) the algorithm can take into account the influence of free surface on floating state with clear principle and good convergence; (2) the algorithm is easier to obtain accurate solutions for both traditional single-convex structures (such as single hull vessel) and multi-convex structures (such as multi-hull vessel, floating offshore platform, etc.), and its computational efficiency is higher; (3) the algorithm can realize the “building-block” modeling mode, which can greatly reduce the workload in multi-condition modeling; (4) the algorithm does not need to rely on foreign third-party graphics platform (such as AUTOCAD, CATIA) , which lays a good foundation for the localization of related industrial software in our country.