Study On Hybrid Multi-transmitting Formula Method And Its Application In Water Wave Simulation

At the design stage, the wave loadings and motion characters of a naval architecture aremajor concerns of the designers. To solve the related hydrodynamic problems numerically, agreat number of researchers pay their attention to a boundary element method based on theRankine source. When simulating ocean waves and their interactions with structures with theRankine source method, people have to truncate the fluid domain at a certain distance fromthe structures using an open boundary. Some wave-absorbing methods are then adopted on theopen boundary to make the simulation close to the real nature phenomenon.However, most existing wave-absorbing methods have limitations, which restricts theirapplications in a lot of simulations. In recent years, Wenyang Duan et al have come up with anew wave-absorbing approach (we call it "H-MTF method" in this thesis), which is the hybridof the multi-transmitting formula (MTF) and the damping-zone method. As their numericalresults show, the H-MTF method has some advantages in absorbing irregular waves.In this thesis, we write some programs based on the2D higher-order boundary elementmethod and3D constant boundary element method in the theoretical frame of potential flow.We model the linear problems of water waves and their interactions with structures using theMTF, damping-zone, and H-MTF wave-absorbing method respectively. By a series ofcomparisons and analyses, H-MTF method’s advantages and application prospects inengineering related to water waves are shown in this thesis.By modeling the2D and3D numerical wave tanks, we find that the H-MTF method canremove the disadvantages of MTF and damping-zone method at a certain extent, and hasexcellent advantages when simulating irregular waves. Also, H-MTF method can avoid thewave-reflection effects of MTF method in3D cases.Wave diffraction problems of a vertical cylinder standing in an open sea are studied inrectangle-and cylinder-shape computational domain. Conclusions can be made that whenusing H-MTF method, the shape of the computational domain and the damping-zone area arenot critical factors to be considered. Thus the H-MTF method has great flexibility to variousproblems, which makes this method potential value in the simulation of real engineeringproblems. Finally, we studied the diffraction problems of single and double cylinders in a3Dnumerical wave tank, which verifies H-MTF method’s possibility of modeling more complex engineering problems.