Research On Mechanical Characteristics Of The Foundation Of Offshore Wind Turbine

In recent years,due to the consumption of non-renewable resources,such as petroleum and coal,has increased On one hand,this raises the concerns about energy exhaustion in the future;On the other hand,the large amount of pollutants produced by the burning of fossil fuels poses a great health threat to human beings around the world and a great risk to the society nowadays.So,the development and utilization of renewable energy are gradually received extensive attention all over the world.As one of the main renewable energy,wind power thus has been rapidly developed and the construction cost of wind turbine generator systems has been reduced.However,with the increased proportion of wind power generation,other issues like the occupation of land resources,the unstable wind,and the noise pollution of onshore wind turbine are emerging.Therefore,people begin to focus on the sea and to exploit the wind resources of it.Because offshore wind energy is much more abundant than its counterpart of the continent.Cost effectively,there is no occupation of land resources for the vast area of the ocean.In addition,the sea is sparsely populated,which benefits the reduction of the noise coming from the operation of wind power units.As a result,the offshore wind power generator will be an important development direction of wind power in the future.Offshore wind resources are relatively abundant in China,but the development of the offshore wind turbine in open sea is far from mature commercial operation,restricted by technology level,technical maturity and reliability.At present,the fixed foundation for wind turbine is still given priority to in our country.However,with the increase of the installed capacity and the weight of the turbine,the requirement for the bearing capacity of the foundation has been continuously raised;thus the pile diameter has been increasing.The Morison formula is conventionally utilized to calculate the sea load of an ocean structure in engineering,whose results is the basis of initial design.But the range of it is merely constricted to the structure of slender,which means it is no longer applicable to the large-diameter monopile foundation.In this way,it is in desperate need to propose a solution,which meets the requirements of efficient computation in engineering,and provides a sufficient accuracy as well.In this paper,a numerical simulation software,based on the potential flow theory and mode superposition method,is developed to calculate the wave-structure interaction of the large-diameter monopile foundation.Different kind of parallel computing technologies are applied in the software.It further improves the superiority of the potential theory,one of whose characteristics is high speed computing;and also quickly offers the result of sea load and structure vibration response of the foundation under different frequency.In order for the verification and comparison,a fixed monopile foundation with a large diameter for the inshore wind turbine is analyzed by STAR-CCM+,a computational fluid dynamic(CFD)software.The analysis has to do with different sea loads under several typical wave conditions(including two regular waves and two irregular waves)and three seabed conditions.The variation of loads on the foundation and the summary of its regularity are derived from comparison among values and frequencies of loads in different conditions,which offers some references for structural design.Moreover,the discrepancy between numerical simulation method and potential method is also analyzed by comparing frequently-used theoretical results stemming from MacCamy and Fuchs,who analyzed the reaction between plane waves and a single cylinder,with the numerical results obtained from the CFD software.The structural vibration response of the monopile foundation under sea load is also analyzed at the same time.