Design And Application Research Of Mooring Systerm For Tidal Current Device

As an important part of marine renewable energy,tidal current has the characteristics of high energy density,clean and pollution-free and rich reserves.With the increasing shortage of traditional fossil energy and more serious environmental problems,the development and utilization of tidal current energy has been widely concerned by various countries.With the actual work conditions,in addition to bearing wind,wave,flow,and other ocean environmental loads.Turbine will lead to a huge horizontal load and overturning moment around the flow field,directly when it worked it will affect the stability of floating tidal station directly.In addition,due to the tidal station works in the shallow water,the mooring chain will be affected by the shock load owing to the tidal turbine.Because of the mooring chain has a relatively small amount of overhang and its deformation can not resist the effects of external loads.The reaserch of shallow water mooring has always been a hot topic,in the design of mooring scheme,if the mooring force is to be increased,the length of submarine lying chain will need to be extended,resulting in the increase of costs and the arrangement of the mooring lines occupying a wider area of water.If the pre-tension of the mooring line is reduced,it will be necessary to reduce the span of the anchor chain and increase the relative length of the lie chain,resulting in an increase of the floating range of the floating body and aggravating the motion response of the structure.Based on the above practical engineering problems,taking the 300 kW horizontal axis tidal current device as the research object,combining with the characteristics of tidal current device and engineering actual conditions,determining the design criteria of mooring system.Firstly based on the three-dimensional frequency-domain potential flow theory,the carrier hydrodynamic coefficients in the regular wave are obtained in the frequency domain analysis.Then the secondary development of the AQWA software is carried out.The hydrodynamic coefficients and real-time exciting force of turbine loaded into the model to couping calculate in time domain.On this basis,based on catenary theory,the displacement of each degree of freedom generated by the floating body under the environmental load is regarded as the static displacement at the top of the mooring chain,and then solving the real-time restoring force of the mooring system under this static displacement.Finally,two designs are proposed for the design of mooring system of 300 kW floating tidal current power station.This paper can provide theoretical guidance and technical support for the design,development and engineering application of floating tidal current power station based on horizontal axis turbine.