Scouring dynamics response of monopile offshore wind turbine based on AFL method
As the most widely used support type for offshore wind power,monopile foundation is commonly surrounded by different degrees of erosion.In previous studies,the detailed features such as blades,engine rooms,and blades were rarely considered in the structural dynamic response after foundations erosion.Instead,the upper structure was simplified as a particle or static state,lacking an integrated numerical simulation method of foundation-structure-load,which was difficult to reflect the vibration patterns of wind turbine structures after foundations erosion.Therefore,to determine the maximum scouring depth of a single pile foundation,the multi beam scanning was conducted in the Puti Island offshore wind farm.Based on the AFL(equivalent embedding length)method,the flexible characteristics of the pile foundation were considered,and the equivalent embedding length of the pile foundation under different scouring depths was calculated.A wind turbine simulation model was established under the joint action of wind and waves,revealing the dynamic response law of a single pile under different scouring depths.It is indicated that the scouring depth is difficult to cause structural resonance,and the overall amplitude of the structure is small.The maximum amplitude of the tower and monopile appears in the F-A(front and after)direction,while the displacement amplitudes in the S-S(side-side)and YAW(vertical)directions are relatively small.It is necessary to focus on monitoring the F-A vibration.As the local scour depth of the pile foundation increases,the structural frequency of the wind turbine structure monotonically decreases.When the scour depth reaches 12 meters,the overall stiffness of the structure is insufficient,and a safety threshold for monopile foundation scour is given.With the method of dynamic response analysis proposed in this paper,safety evaluation for the different scouring depths can be conducted in engineering.
monopileoffshore wind turbinesmulti-beam sweep measurementscouringinherent frequency
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