Research On Hydrodynamic Performance Of Pile Array Under Wave Action

In recent years, with the development of offshore oil platform, navigation, offshore wind power, cross-sea bridge et al, the research of water wave loads on offshore structures has received widely attention. The pile structures are widely used in various offshore structures. It is necessary to discuss the hydrodynamic performance of pile structures under wave action.Recently, the study method about wave force loads on grouping piles have most focused on physics experiment in the domestic and overseas, and numerical simulation method is relatively used less. In research content, the discusses of structure of piles have most concentrated on bi-piles in tandem and parallel arrays, three piles in tandem and parallel arrays, and four piles in squares array, these research results can’t be used on complicated pile structures. About influencing factors, most consider the effect of the factor of KC, Reynolds number Re, the location of piles, the distance between piles, and the diameter of pile, but few considers the direction of wave. Considering above questions, this work aims to conduct a systematic investigation on the hydrodynamic characteristics of pile array with both experimental and numerical method.Firstly, the hydrodynamic performance of five piles array under waves is studied experimentally, including regular wave and irregular wave. In the regular wave part, being based on wave forces on a single pile, this paper intensively considers the influence of the factor of KC and the direction of wave to grouping pile effect. Finally, it gives the distribution ratio of wave forces load on each pile. In the irregular wave part, being basing on the research contents of regular wave, we focused discuss wave forces on each pile while wave forces load on pile array reach the maximum value and gives the force percentage of each pile. The research of irregular wave force is considering more practical application, and it can offer some suggestion for engineering design.Secondly, for numerical simulation, numerical model is developed based on FLUENT software,3-D Reynolds-Average Navier-Stokes equation and k-ε turbulence model, which considers real viscosity, and finite volume method to discretize governing equation. A three dimensional numerical wave flume is developed based on the source wave-generation method and the source wave-dissipating method, which add source in the continuity equation and momentum equation, and the VOF method to capture free surface. We compare numerical results with theoretical results of second-order Stokes wave to check the efficiency of wave generation and compare numerical results with experimental results of single pile and grouping piles interaction with wave to confirm the efficiency and accuracy of this wave flume dealing with hydrodynamic problem of three dimension structures.Finally, based on the above numerical work, we further conduct the research of hydrodynamic characteristic of grouping piles under wave action. Considering the factor of KC and the direction of wave, we also take into account the influence of relative spacing between piles l/D. At last, we investigate the force mechanism through analyzing field of vorticity around pile array.