Frequency-Domain Numerical Solution For Interaction Between Waves/Wave-Current And Three-Dimensional Bodies In Channels

With the development of the exploration and utilization of marine resources,many new types of marine structures and devices are constantly emerging.In the design process of these structures and devices,when lacking relevant design experience,in addition to theoretical analysis and numerical calculation,model experiments should be carried out in the wave tank or basin to validate.However,compared with the open-sea condition,the fluid domain of the wave channel is bounded with channel walls,such that the reflection of the side wall has a certain influence on the experimental results.Similarly,when a ship is moving in the narrow waterway,the wave interference between bodies and boundaries will affect the ship maneuvering condition.Thus,having a good understanding of how the side walls affect the hydrodynamic characteristics of the structure is essential.In addition,for a specific structure in a wave channel,the extraordinary transmission phenomenon may occur at certain frequencies,which may cause great damage to the structure and affect the safety of the practical engineering.Therefore,it is necessary to conduct in-depth research on the extraordinary transmission phenomenon.Based on the above motivations,under the framework of potential flow theory,the frequency-domain analyses of waves or wave-current interaction with three-dimensional bodies in the wave channel are carried out in the present study.Firstly,based on the hypersingular boundary element method,the extraordinary transmission phenomenon is examined for waves propagating through gaps of vertical thin barriers in channels.By accurately solving the Hadamard integral including a hypersingular kernel,the reflection and transmission coefficients are calculated.The influences of different influencing factors on the extraordinary transmission and wave height are studied.It is found that proper arrangement of barriers in a channel can avoid the occurrence of extraordinary transmission phenomenon.The research results can provide relevant design experience for the practical engineering,such as the layout of the breakwater in ports along estuaries to reduce the possibility of extraordinary transmission.For a body with arbitrary geometery,the second-order interaction between monochromatic or bichromatic waves and three-dimensional floating bodies in the wave channel is studied.Compared with the first-order problem,the evaluation of the free surface integral,the body surface integral and the control surface integral,which have a great contribution to the second-order results,should be further considered in the second-order analysis.The integral transformation is applied for the accurate calculation of the free surface integral and the body surface integral.For the control surface integral,the indirect method and the direct method are used.In the direct method,the expression of the complete second-order locked potential in the wave channel is given,such that the direct method can obtain the control surface integral more directly than the indirect method.The results of the two methods can be used as a check for each other.It is found that the second-order hydrodynamic properties of a body in a channel are affected more seriously than th e linear ones,so much care should be taken in using laboratory measurements to predict the nonlinear results for the open-sea conditions.Finally,the influence of the current is further considered.The wave-current interaction with three-dimensional floating bodies in channels is studied.First,the boundary integral equations for the steady potential and the unsteady potential are established,respectively.In the process of solving the unsteady potential,the unsteady potential and the Green function are expanded with the current parameter.With the far-field expressions of the unsteady potential ang the Green function,two sets of boundary integral equations with higher computational efficiency are obtained.Then,the higher order boundary element program is set up.The numerical model is validated by the numerical relations.It is found that the current may cause more significant side-wall effects.The numerical results provide a basis for the analysis of relevant experimental results,such as seakeeping experiments.