Modification Of Ship Shape NURBS Curve

Ship lines design has been playing the important role in ship design. It is the Main goal of the ship builder that how to improve the level of ship lines design to high grade. Since the ship lines, including straight line, conic curve and free one, are very complex, it seems to be impossible to present them by an uniform formula without NURBS. But, because NURBS is abstract ,the modification of the ship line during ship design is in the conventional method .It is an obstacle for integration of ship design. So that, the theory and key technology of the NURBS curve are very important. In addition, integral algorithm of NURBS curve is one of the points in this paper.This paper based on NUBBS expression of ship shape, using the theory of modification ,deals with three problems in ship shape modification: Modification of sectional area coefficient curve, Modification of UV variation of hull form and Small Water-plane Area Twin Hull (SWATH) ship line design.This paper give a simple method of modification of sectional area coefficient curve. with logical variation function, the method can satisfy the requirement of ship design, and example is given indicating its practicability.Projection function can be used in modification of UV variation of hull form. Based on boundary conditions analysis ,solving partial differential equations ,receive projection function of modification of UV variation of hull, so that satisfy the requirement of ship hydrodynamic performance.The cross section of the submarine-body of SWATH ships can be unified expressed by NURBS. By using the projection transform function of NURBS, which is described in this paper, we can get interpolation of the cross section of the submarine-body formed by arbitrary curves conveniently and intuitively, and can express and transform arbitrary curves by using NURBS. It is very significant to the unified expression of hull form.