Evaluation of drag coefficient variation in transit mode on leg & spud can of DP Jackups vessel

The Marine and Oil & Gas industries have increased interest in Self Propelled DP Jackups vessel to enhance the overall operational efficiency. The self-propelled jackups vessel has numerous applications such as well intervention, wind farm installation, repair, accommodation, service etc. in this cost optimization process. However due to closed proximity of operation (i.e. near to hydrocarbon platforms or other offshore assets), it has gigantic risk during the Simops Operation. The Simops Operation of Dynamic positioning and Jacking operation has a grey area in force calculations for DP system on board which use mathematical model. The input from position reference sensors, environmental sensors to calculate relative position based on position, heading, speed and rate of turn inputs for station keeping/ DP intended operation and finally issue thrust output command. The system continues to monitor the position by taking its feedback and comparing with calculated vessel position. However, many DP jackups does not have system for hydrodynamic force measurement of leg & spudcan. This is mainly due to drag coefficient of complex leg and Spud Can geometry. The drag coefficient plays vital role in force calculation and due to non-standard shape currently industries follow approximation method. This will increase risk in station keeping under different condition and failure cases. The intension of this study is to find the gap in existing force calculation, which is affected by drag coefficient. During the CFD analysis evaluation the effect of marine growth, leg shape, spud can, leg transit speed under variable environmental conditions are considered. The software use for CFD analysis is Ansys Aim. The vessel data used for the simulation purpose are from most popular design of jackups vessel used in offshore O&G and wind farm industry. The study will provide drag coefficient variation in transit time domain, which has large impact on force calculation estimation for DP System.