A Practical Assessment Method in Prediction Minimum Propulsion Power to Ensure Safe Navigation of FLNGs and FPSOs in Adverse Condition

Abstract Self-propelled FLNGs and FPSOs are built to navigate from the yard to the field and to avoid typhoons in the field. In this case, the minimum propulsion power required must be determined taking into account adverse weather condition. The minimum propulsion power is estimated based on target transit speed and weather conditions. With the current technology, neither model tank test nor CFD provide satisfactory estimation results in this prediction. Model tank testing is expensive and available model basins are very limited. CFD does not have an established method for such complex calculation. In this paper, estimation is performed using a comprehensive method to calculate propulsion power for given weather conditions. By solving the two-dimensional force equations, the propulsion power can be predicted by calculating transit speed, drift angle, thrust and steering angle. Predictions are made for a conventional propeller-rudder system and multiple azimuth thrusters system, and the results are compared with model tests. Furthermore, the typhoon avoidance criteria with a given propulsion system are presented when the conditions are not specified.