Study of drag force acting on various types of dp jack-up vessel legs

Nitin D. Thulkar, Satoru Yamaguchi, Koki Ebihara

Research output: Chapter in Book/Report/Conference proceedingConference contribution


The Dynamic Positioned (DP) Jack-up vessels currently use two popular designs of legs, (i.e. rack & chord lattices and cylindrical leg type). These two leg designs are popular and various experiment conducted in the past to evaluate the drag coefficient and drag force of these legs, but they are only available in a steady state condition. The intention of our experiment is to measure drag force and compare with CFD results. In DP vessels, mathematical model of the vessel first estimates the environmental force acting on the vessel, by using real time sensor data and then generate the counter balance thrust. The output command of force and angle is then sent to the available thrusters. However, usually, DP Jack-up vessels do not have sensor to measure the hydrodynamic force of leg &spudcan. Presently, each DP control system manufacturer for Jack-up vessels uses its own mathematical technique to achieve stability of station keeping during simultaneous operation of dynamic positioning and Jacking operation (SIMOPS). Moreover, this sensor less DP system tuning is unknown to the industries. Our intention of these experiments is to measure the hydrodynamic forces, in order to understand how the evaluated forces is altered under different environmental and operational conditions in SIMOPS operation. To start with, we first decided to measure drag forces when leg & spudcan moves in UP/DN direction under variable environment current. Both CFD and tank experiment is done using 3D prototype scale model of a cylindrical leg. The experimental limitation is also defined based on the tank facilities. The data is recorded during lowering and raising of the leg to see the effect on the drag force of leg-spudcan. The experimental data are recorded for current, leg speed; drag forces etc. with respect to time and average value considered for a steady state experimental case period. The evaluated results are compared with CFD results and show similar trends with acceptable error. The CFD analysis also carried out on a full-scale leg diameter to see the drag force trends. In order to understand the effect of seabed on the overall hydrodynamic force, cases were studied in which the leg was kept just a 0.1 m above seabed.

Original languageEnglish
Title of host publicationProceedings of the 29th International Ocean and Polar Engineering Conference, ISOPE 2019
EditorsJin S. Chung, Odd M. Akselsen, HyunWoo Jin, Hiroyasu Kawai, Yongwon Lee, Dmitri Matskevitch, Suak Ho Van, Decheng Wan, Alan M. Wang, Satoru Yamaguchi
PublisherInternational Society of Offshore and Polar Engineers
Number of pages7
ISBN (Print)9781880653852
Publication statusPublished - 2019
Event29th International Ocean and Polar Engineering Conference, ISOPE 2019 - Honolulu, United States
Duration: Jun 16 2019Jun 21 2019

Publication series

NameProceedings of the International Offshore and Polar Engineering Conference
ISSN (Print)1098-6189
ISSN (Electronic)1555-1792


Conference29th International Ocean and Polar Engineering Conference, ISOPE 2019
Country/TerritoryUnited States

All Science Journal Classification (ASJC) codes

  • Energy Engineering and Power Technology
  • Ocean Engineering
  • Mechanical Engineering


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