Resonant frequencies analysis and vibration control of fluid in three-dimensional (3D) moonpool: Analytical modeling and experimental study

摘要

Moonpool widely exists in the fields of offshore oil and gas resources drilling, marine energy development and so on, and also has important applications in special ships and surface ships. The aim of this paper is to present an accurate three-dimensional modeling method and analyze resonant frequencies of fluid in three-dimensional moonpool. Based on the three-dimensional potential flow theory, the governing equations and boundary conditions of the fluid in the three-dimensional moonpool are established. According to the characteristics of the governing equations and boundary conditions of the fluid in the moonpool, the velocity potential of the fluid in the moonpool is expanded into the form of the sum of three-dimensional Fourier series and smooth auxiliary functions. Then, the velocity function is introduced into the governing equations and boundary conditions, so that the complex partial differential equations can be transformed into a set of simple linear equations, and the resonance frequency of the fluid vibration in the moonpool can be obtained by solving the linear equations. In order to verify the validity of the three-dimensional accurate model proposed in this paper, numerical examples and experimental verification are carried out, and then the numerical and experimental results show that the proposed solution has good convergence accuracy and calculation accuracy. On this basis, the effects of the length, width and water depth of the moonpool on the resonant frequencies and modes are discussed, and the natural vibration behavior control of the fluid in the three-dimensional moonpool are analyzed in detail. In this work, the three-dimensional analytical solution is proposed for the first time to study the natural vibration characteristics of the fluid in the three-dimensional moonpool, and its correctness is verified by the model experiment. At the same time, some bright research results are also given, which is of great engineering significance for understanding the resonant frequencies and modes of the fluid in the complex moonpool structure.