극지용 부유식 플랫폼을 위한 빙하중 생성 모듈 개발 및 위치 유지 성능 평가

Abstract

To assess the station-keeping performance of floating structures in the arctic region, the ice loads should be considered along with other environmental loads induced by waves, wind, and currents. However, present methods for performance evaluation in the time domain are not effective in terms of time and cost. And also the standard procedure to be used to analyze the station-keeping performance of a floater considering ice loads has not been established yet. In this paper, ice loads generation module is proposed based on the experimental data measured at the KRISO ice model basin. Using the results of a captive model test conducted in multiple directions, the statistical characteristics of ice loads were analyzed and processed so that an ice loads corresponding to an arbitrary angle of the structure could be generated. The developed module is connected to commercial dynamic analysis software (OrcaFlex) as an external force input. Then, station-keeping simulation in the time domain was conducted in complex environmental loads with ice-induced forces were generated and applied to a ship type floater with dynamic positioning and mooring systems. The effectiveness of heading control with a dynamic positioning system is analyzed to evaluate the improvement of the performance of the station-keeping system in the ice conditions. Two different station-keeping systems with mooring only and mooring with a dynamic positioning system. Position offsets and mooring line tensions for the two scenarios were compared with maximum values and most probable maxima (MPM) values. The results of the simulation showed that the heading control can reduce 8.2% of MPM values for the mooring lines and improve the station-keeping performance by about 16.3%. The validity of the station-keeping system that was designed was confirmed, and it is expected that the specification of mooring lines can be relaxed with the heading control. keywords : Dynamic positioning(DP) assisted mooring, Statistical ice loads generation, Time domain simulation, Station keeping performance evaluation, Arctic floating structures, Heading control