Study of the lift effect on wind load estimation for a semi-submersible rig using the maritime atmospheric boundary layer model

Abstract

Wind loads on a semi-submersible rig were investigated using computational fluid dynamics. A maritime atmospheric boundary layer model for wind profile was implemented such that the wind profile shapes were retained throughout the computational domain. Wind loads on the semi-submersible rig were calculated under the maritime atmospheric boundary layer and matched well with the results from wind tunnel within a ±20% error. Among the topside structures, five structures including deckbox were selected and analyzed on the contribution to the wind load, particularly overturning moments by decomposing the moments into drag and lift components. Overall, moments ignoring lift components tended to overestimate overturning moments by approximately 20% at maximum. The majority of the lift components originated from the deckbox, which served as a lifting body owing to the accelerated streamlines between the waterline and the bottom of the deckbox.

Keywords

• Maritime atmospheric boundary layer
• OpenFOAM
• Semi-submersible rig
• Wind load