Research On The Motion Of The Floating Body In Waves Based On Higher Order Panel Method

In shipbuilding engineering and naval architecture, the motion of vessels and other floating structures in waves is always a problem which people pay more attention. For ships and ocean structures, such a problem matters because it is a key fact which involving safety,operational ability and comfort of crews. Modern theory of motion of floating body in waves was founded in 1950s, after that both theoretical and experimental method for predicting motion response of floating body has achieved booming development. But predicting motion response by experimental method is expensive, time costing and not mentioned the labor it needs. By theoretical method, Using CFD technology which stems from viscous flow theory is also time consuming and the result largely depend on the quality of the grid. Since 1960s,panel method which is founded upon potential theory and also called boundary element method is thriving. Although compared with viscous flow theory, the potential flow theory is not the exactly physical description of the phenomenon. But such a theory has an advantage that it not only can be introduced to evaluating the response of floating body in waves but also is accurate enough for engineering and reasonable time consuming.In the research of this paper, the motion of floating body in wave is calculated based upon three dimensional potential theory, a higher order panel method is developed independently to solve such a problem. In the panel method this paper presented, non-uniform rational B-spline is used to fit the body surface and boundary elements. Source and potential is described by isoparametric element.For the singularity of the integral, a singular kernel expansion method is used to isolate the singular part of integral. After that a method which could calculate Cauchy principle value could be used to solve this problem. Because NURBS is introduced to describe the body surface, compared with describing surface by isoparametric element, the method used in this paper could keep continuity between panels, improve the convergence and weaken the singularity of the integral.The validation of the program was done by considering unbounded flow around a sphere.Calculation results of radiation and diffraction problem of a sphere which is near the free surface and without speed. Calculation results of radiation problem of a hemisphere without speed. Calculation results of radiation problem of of Wigley form hull with a constant forward speed. The RAOs of real ship in waves were calculated. Multi-body coupled problem is also considered in this paper, the RAOs of double real ship in waves were also calculated.Because the method presented in this paper could evaluating the response of vessels and floating structures in waves by using less boundary element and consuming reasonable time The research will have a very extensive application.