| The abundant marine resources have brought prosperity to offshore engineering operations.In many resource development operations at sea,cable components are often required to perform certain functions.In this paper,the analysis of submarine cable installation conditions and the dynamic response analysis of CALM system are studied.Based on Orca Flex software,the calculation model of submarine cable and mooring chain adopts natural catenary model in static state and lumped mass-spring model in dynamic state.In analyzing the stress conditions of submarine cable in laying,the model of the submarine cable+installation vessel is first established,in which the movement of the installation vessel is previously input as a boundary condition at the upper end of the submarine cable.The wave load calculation is performed using the Dean Stream wave theory.the environmental conditions to be calculated as wave height 1.0m~3.0m,wave period 5s~13s,wave direction 0°~180°and current direction 0°or 180°,were determined and maximum tension,minimum tension and minimum bending radius of submarine cable under different Layback and different environmental conditions were calculated respectively.Finally,the API specification was used to check and determine the required installation environment conditions and the appropriate Layback value.In addition,the sensitivity analysis of waves,currents,water depth and self-weight was carried out,and the characteristics of their influence on the cable tension and bending radius of the submarine cable were summarized.When analyzing the CALM system,the six catenary anchor chains and buoys are mainly studied.The environmental parameters of once-a-year and once-in-a-century are selected.The waves are simulated by JONSWAP spectrum.The speed and direction of wind and current do not change with time.Refer to the DNV specification,the working conditions with different environmental directions were determined.Then the dynamic response of the mooring chain tension and the buoy movement was calculated.On the basis of analyzing the response,changing the random wave seed number,the peak value of the mooring chain tension response,the buoy displacement response and the hawser tension response was calculated and selected,then using the Gumbel distribution function,the corresponding statistical extremum was obtained.According to the specification,the mooring chain tension and the buoy displacement are satisfied with the requirements.Finally,by comparing the response results of the CALM system under different pre-tension of mooring chain,the influence of pre-tension on the movement of the buoy and the tension of the mooring chain was discussed. |
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