Numerical Simulations of ice forces on the Kulluk: the role of ice confinement, ice pressure and ice management

Abstract

The interaction of managed ice covers with a wide structure is examined. Numerical simulations are used to simulate the modes of ice cover deformation and forces on the structure. The objective of the present work is to validate the performance of the numerical model using historical data recorded during operations of the Kulluk in the Beaufort Sea during the 1980s and early 1990s. This paper is the last part of an investigation aimed at developing an approach for modeling managed ice interaction with wide moored structures. Previous papers examined the role of the mooring system (Sayed and Barker, 2011) and the effects of ice cover confinement and managed floes sizes . The focus of the present paper is on providing quantitative comparison between predicted ice force statistics and observations.The numerical model is based on solving equations describing the conservation of mass and linear momentum together with a plastic yield criterion that describes ice properties. The managed ice cover consists of a heterogeneous ensemble of relatively small floes. The floes are assigned varied thickness values in order to reflect field conditions. The simulations address a class of interaction scenarios corresponding to confined managed ice. As the ice cover is driven within confined boundaries, pressure conditions arise. These conditions are of interest to designers since forces are considerably higher than those corresponding to unconfined ice covers. The solution of the governing equations simulate the evolution of the distributions of ice thickness, concentration (or coverage) and stresses. The resulting ice forces, including peak values, averages and rise-time of forces, are compared to field measurements. The influence of ice thickness and velocity on expected ice forces is also examined.

Image Processing for Identification of Sea-Ice Floes and the Floe Size Distributions

“…From (12), we can find that, although μ varies with the magnification ratio of the image, the relationship between different coordinates will not change. This is because the influence of μ is counteracted based on equations ( 8)- (11). Consequently, the relationship between the image coordinates and the orthorectification coordinates is a function of the shooting angle ϕ and the camera's (vertical) field of view 2θ.…”

Simulations of the StationKeeping of Drillships Under Changing Direction of Ice Movement

“…Previous papers reported on the development and validation of a numerical model of ice deformation and interaction with moored drillships (Sayed et al, 2012a, and2012b). Previous papers reported on the development and validation of a numerical model of ice deformation and interaction with moored drillships (Sayed et al, 2012a, and2012b).…”

“…The model has been validated, to the extent possible, through comparisons with historical Kulluk's observations (Sayed et al, 2012a;Sayed et al, 2012b;and Sayed and Barker, 2011). The response of a rigid body representing the drillship, which is supported by a mooring/thruster-assisted system, is incorporated into the ice dynamics model.…”

Image processing for ice floe analyses in broken-ice model testing

“…• Individual ice floes identified by the image processing system, can be used to initialize high-fidelity numerical models, such as those in Daley et al [16], Vachon et al [17], Sayed et al [18], Sayed et al [19], Gürtner et al [20] and Metrikin et al [21]. Individual snapshots of identified ice floes can be used to validate the numerical models at various moments in time by matching the simulated ice fields with the actual ones.…”