Numerical Simulation Of Ship Wake Based On Wave Pattern Measurement And Analysis Of Ship Model Tests

The diversified modern high-speed ships have come out continually and gone into service, which makes their wake-waves serious channel security and environmental problems, and therefore makes the relevant experimental researches and numerical researches turn into researches of general interest in ship field. With the development of computational fluid dynamics (CFD) and computer technology, the experimental and numerical researches about ship wake-waves have made some progress. Undoubtedly, the study is important to designing and developing lower-wake-wash ship forms, and also solving the security, economical and ecological problems arising from high-speed ship wake-waves.A combined experimental and theoretical method is used to implement the numerical simulation of wide-range ship wake-waves, by means of wave pattern measurement and wave pattern analysis of model tests in conventional towing tanks.Model tests are carried out in the towing tank in Wuhan University of Technology. And the models are made according to high-speed slack bulge displacement series Model 100A. Wave collection system consists of a sensor and five wave probes. Under different Froude number, a series of wave height data and resistance data of NPL monohulls and catamarans are obtained through five longitudinal cuts. The effects of the position where wave height was collected on the wave pattern analysis result based on longitudinal cut method are discussed, (through) presenting the comparison of the wave pattern coefficients derived from wave pattern analysis with that from (1+k) method using the wave height data from longitudinal cuts collection.Two theoretical methods are adopted in this paper. One is the wave amplitude spectrum function computed by Fourier transform. The theoretical formulas for the longitudinal cut method are derived. And the corresponding numerical simulation results are presented. The other is the equivalent-singularity-distribution method. The principle and numerical treatment of this method are described. NPL monohulls and catamarans are selected as computational examples. The corresponding wave amplitude spectrum function is derived from wave height data obtained from longitudinal cuts, and then simulate numerically far-field waves. The decay of computed far-field waves shows that the numerical simulation result is reasonable.Besides, using equivalent-singularity-distribution method based on principle of images, a way to eliminate wall reflection in the signals from wave pattern measurement and lengthen the valid signal segment of wave measurement is discussed.Based on the above-mentioned research results, a systematical procedure for numerical simulation of wide-range ship wakes are formed, which consists of longitudinal cut of wave pattern measurement in conventional towing tanks, equivalent-singularity-distribution method based on principle of images, wave pattern analysis and the free-wave amplitude spectrum method.