基于曲面表达的几何特性计算及其在船舶工程中的应用

船舶静力性能计算中主要涉及到与水线面、横剖面、排水体积和舱容等相关的几何特性计算,在阻力和适航性等性能计算中还要对湿表面积进行计算,以便在设计阶段对船体外形的优劣进行评估和分析,为线型的进一步优化提供依据.为了更精确地计算相关的船舶性能,文章提出了基于曲面表达的相关2D或3D几何体几何特性计算新方法.该方法首先将所表达的曲面离散成四边形或三角形单元,将空间区域分割成若干广义棱柱,再通过四边形、三角形和广义棱柱的几何特性的组合,分别计算界定平面、曲面或空间区域的几何特性.对解析曲面进行NURBS表达,对其截面积、局部表面积和体积及几何特性进行计算,其结果与解析法计算的精确解非常接近.将该方法具体应用于实船的相关计算,结果表明了其可行性、合理性和精确性.

Geometric properties calculation based on surface representation and its application to ship engineering

The geometric properties calculation,related to a ship's waterplane, transverse section,underwater volume,and hold capacity,plays an important role in determining the vessel's static performances.The wet surface area is computed in the resistance and seakeeping performances calculation in order to evaluate and optimize a ship's form.However,for a more precise calculation of a ship's performance,a new algorithm is presented that calculates the 2D or 3D geometric properties based on surface representation.After the represented surface was discretized into quadrangular or triangular elements,the geometric properties of the limited plane,curve surface,and volume were calculated respectively combining the ones of quadrangles,triangles,and generalized prisms.Applying this method,the properties of the sectional area,partial surface area,and volume bounded by analytical surface were calculated based on the non-uniform rational B-spline(NURBS) representation of them with the result coming close to the analytical solution.The related calculation result of a full-scale ship based on this method verifies its feasibility,rationality,and accuracy.