Numerical Simulation Of Local Scour Around The Offshore Wind Turbine Based On The Moving Boundary Method

The local scour around the offshore wind turbine foundation has negative impactson the foundation stability, and it is an important issue of the research on the offshorewind turbine foundation. In this thesis, a three dimensional numerical model of flowis established using the open source software OpenFOAM to reproduce the localscour around the foundation. Based on the mesh topology transformation, a set ofmethod with respect to the bed moving boundary is developed to simulate the bedelevation. The main research contents and relevant conclusions are summarized asfollows.(1) Based on the OpenFOAM, a three dimensional numerical model of flow isdeveloped. The open channel flow and flow around a cylinder under different bedroughness are simulated with the discussed model. The vertical distribution of flowvelocity and the flow field structure around a cylinder are analyzed and tested againstthe experimental data. The presented model is proved reasonable and accurate by thecomparison.(2) Based on the conversion utilities for mesh topology, a set of computationalgrids generation method describing the moving bed boundary is proposed to simulatethe bed morphology. Based on the concept of equilibrium of critical bed shear stress,as well as the numerical model of flow and the moving bed boundary approach, athree dimensional numerical model of local scour around structures under flow isdeveloped.(3) The local scour around a cylinder on laboratory scale and the in-situ scouraround the pier of Si-Lo Bridge are simulated respectively using the scour model. Thenumerical results about the maximum depth and morphology of equilibrium scour pitare compared with the experimental data and the in-situ measured data. The consistentdeveloping trend between simulated and measured results indicates that the scourmodel can predict the local scour around structures.(4) The presented scour model is applied to simulate the local scour around thecomplex bucket foundation of Xiangshui offshore wind farm. The numerical results ofthe maximum depth and morphology of equilibrium scour hole provide references forthe design of the complex bucket foundation.