Numerical Calculation Of Wavemaking Resistance For High-Speed Displacement Trimarans

Trimarans have many advantages in performances and open up a vast range of prospects for applications.The research on them becomes more active and has made progress recent years.One of the key problems in the hull design and optimization is how to forecast the ship resistance quickly and accurately.With the development of computational fluid dynamics and computer technology,the forecasting precision of ship resistance has increased.The numerical calculation of wave resistance by a raised panel method based on NURBS(Non- Uniform Rational B-Splines)for high speed ships is discussed,and numerical examples of the wave-making problem for trimarans is presented.This is a high-precision and the generalized high-order panel method.The body surface,free surface and every physical quantities to be solved are expressed as a whole nth-order continuous surface,or several surfaces if needed,in this method.It is of better numerical characters than conventional panel methods.Raised panels above the free surface combined with collocation-point shifting up-stream are used to satisfy the radiation condition numerically.Numerical treatment with transom-stem flow is rather difficult.In this thesis, transom stern boundary condition is implemented numerically in physical model of smooth flow off the transom edge tangentially,and better results obtained.A non-uniform rational B-Splines(NURBS)method to design curves and surfaces is summarized and fits of three-dimensional hull surface adopt the skinning method is carried out.An expansion to the calculations in restricted waters is considered in numerical calculating programs.The programs can generate NURBS surfaces from the input of discrete geometry data of water bottom or bank,and calculate corresponding problems.Wigley hull and NPL hull are selected as computational examples.The wave making resistance and wave patterns of high-speed displacement ships,both mono-hull and catamaran in deep water and shallow water respectively,are computed.Finally,wave-making problem of trimarans is presented.Compared with the experiment data and calculated data in other references,the results are satisfactory.