Numerical simulations of ice interaction with a moored structure

• Main Authors: Sayed, M., Barker, A.
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2011
• Subjects: Beaufort sea; conservation of mass; cut-off; fixed structure; floating ice; horizontal planes; ice concentration; ice cover; ice model; ice thickness; ice velocity; linear spring; Mohr Coulomb yield criterion; moored structures; mooring stiffness; mooring system; numerical models; peak force; rigid body; transient forces; vertical movement; computer simulation; constitutive equations; equations of motion; mooring; stiffness; ice; Arctic; Beaufort Sea
• Online Access: https://nrc-publications.canada.ca/eng/view/object/?id=a8008ae1-0685-4aa0-ace9-18f9ba7ea065; https://nrc-publications.canada.ca/fra/voir/objet/?id=a8008ae1-0685-4aa0-ace9-18f9ba7ea065

The paper describes a numerical model of floating ice interaction with a moored structure. The model is based on solving the equations for conservation of mass and momentum together with the constitutive equations for the ice cover, as well as the equations of motion of the moored structure. The ice cover is considered to follow a cohesive Mohr-Coulomb yield criterion with a tension cut-off. The structure is treated as a rigid body supported by a linear spring that can move in the horizontal plane. Vertical movements are neglected. A depth averaged version of the ice model is used, whereby stresses and velocities are averaged over the depth. The model accounts for variations of ice thickness and clearing around the structure, but not clearing under the structure. The simulations addressed cases resembling conditions of the Kulluk deployment in the Beaufort Sea during the 1980s. The data of the Kulluk was examined in order to determine the stiffness of the mooring system. Simulations produced distributions of ice concentration, thickness and pressures, and forces on the structure, as well as the resulting velocities and displacements of the structure. The resulting forces increased with increasing ice thickness and with increasing ice velocity. The predicted forces show good agreement with measured peak forces. The role of the mooring stiffness was also examined. The mooring system causes a moderate reduction of forces below those obtained for a fixed structure. A relatively low stiffness was shown to reduce the transient forces. The forces eventually rise to approach those for stiffer mooring as ice continues to impinge on the structure. Copyright 2011, Offshore Technology Conference. Peer reviewed: Yes NRC publication: Yes