Preliminary Analytical Formulation of Ice-Floater Interactions Including the Effect of Wave Load

2018 ◽  
Author(s):  
Aziz Ahmed ◽  
M. Abdullah Al Maruf ◽  
Arun Kr. Dev ◽  
Mohammed Abdul Hannan
Keyword(s):  
Oil And Gas ◽  
Ice Sheet ◽  
Sheet Thickness ◽  
The Arctic ◽  
Total Force ◽  
Wave Load ◽  
Incoming Wave ◽  
Total Load ◽  
Ice Load ◽  
Level Ice

Diminishing ice presence in the Arctic provides the potential for extended operable period for oil and gas exploration in the Arctic. Floaters are a flexible solution for such scenario whereas they can fully take advantage of the extended drilling season as well as operate in other harsh environment regions during the off-season. Such floaters can disconnect and reconnect to avoid large ice features such as icebergs and multi-year ice ridges. However, they still need to encounter relatively large level ice. Accompanying icebreakers will ideally assist in breaking the level ice into manageable pieces. The interaction of such level ice floes with floater has a significant influence on the dynamic ice load on the floater and resulting mooring load. There is significant uncertainty in the simulation of level ice-floater interaction numerically. Most of the current research focuses on the influence of ice breaking and subsequent flow of the broken ice around the floater. However, the hydrodynamic load due to the incoming level ice will also affect the response of the floater, which is usually not simulated. A recent study simulated the multibody hydrodynamics of level ice and floater Such multibody hydrodynamic analysis is computationally expensive, and complexity in the modelling is a hindrance to its implementation in the design phase. The present study, therefore, employs a conservative estimation to include the effect of wave load on the floater in addition to the ice load. Parametric studies are performed to estimate this effect by varying the incoming wave amplitude and wave period, ice sheet thickness, ice drift velocity, floater’s hull angle, mooring stiffness and the distance of large ice-sheet from the floater. Significant impacts of waves on the floater in terms of total force are observed which clearly reflects the importance of this study. The effect of mooring stiffness on total load is also investigated at the end of this study which can be considered as a foundation for further research on optimizing the mooring stiffness for such kind of arctic floater.

A Coupled Dynamic Ice-Load and Moored Floater Interaction Parametric Study for First Year Level Ice

2016 ◽  
Author(s):  
Aziz Ahmed ◽  
Anurag Yenduri ◽  
Ritwik Ghoshal ◽  
Zhuo Chen ◽  
Ankit Choudhary ◽  
...  
Keyword(s):  
Parametric Study ◽  
Oil And Gas ◽  
Time History ◽  
Full Scale ◽  
The Arctic ◽  
First Year ◽  
Mooring System ◽  
Oil And Gas Exploration ◽  
Ice Load ◽  
Level Ice

Arctic remains the final frontier in the oil and gas exploration regime. The diminishing presence of ice opens up the region for longer and wider exploration. However, even with the assistance of ice management, the threat of broken first-year level ice stays ubiquitous. Calculation of ice load for such ice features bases on the established formulation developed by observation from full-scale measurements and model test data over the years. However, the formulation mostly relies on the data derived from fixed structures or icebreakers. Such estimations of ice load do not account for the stiffness compliance afforded by mooring system of a floater, such as a semi-submersible or a spar. A floating oil and gas exploration system offers a number of advantages over the fixed platforms, such as the option to deploy elsewhere during the off-season in the Arctic as well as connecting and disconnecting during severe ice events such as an approaching iceberg or multi-year ice ridge. However, the current practice of employing dynamic ice load time-history available in ISO19906 or similar codes fails to account for the presence of the mooring system on these floating platforms, directly resulting in a lack of confidence in the derived response of the floater. This study aims to address this issue by developing a dynamic ice-load time-history algorithm, which, can readily couple with commercially available hydrodynamics and mooring system analysis software. This investigation puts forward the hypothesis that the evolution of ice load vs. ice feature displacement with respect to the structure remains same for both fixed and floating structures. However, the underlying assumption is that the size of the ice features remains comparable. This hypothesis accounts for the prominent influence of the size effect on the breaking strength of ice. The difference between the behavior of a fixed and a floating structure under ice load is due to the relative motion between the floater and the ice feature. The developed coupled ice-load-function accounts for this by including the relative displacement between the floater and the ice feature in the formulation. This study uses the semi-empirical formulation originally derived by Croasdale to calculate the main ice load components for a fixed structure with downward breaking slope. Subsequently, this study uses this coupled ice load subroutine to compare against the full-scale measurement data found in the literature for a floater with downward-sloped hull specifically designed to assist in ice breaking. A comparison against the peak load observed during full-scale measurements on a floater in the Arctic waters validates the proposed approach. Next, this study utilizes the coupled analysis to derive the displacement, velocity, and acceleration response of the studied floater for a range of ice parameters, such as the drift speed and thickness. Additionally, this study performs a parametric study by varying the downward breaking slope angle of the floater, the mooring configuration, and the water depth. Finally, this study summarizes the observed behavior of the floater under different ice parameters as well as floater shape and mooring systems parameters.

Advanced Weathervaning in Ice

2011 ◽  
Author(s):  
William Hidding ◽  
Guillaume Bonnaffoux ◽  
Mamoun Naciri
Keyword(s):  
Rapid Change ◽  
Ice Sheet ◽  
Model Tests ◽  
The Arctic ◽  
Mooring System ◽  
Sudden Increase ◽  
Time Step ◽  
Ice Loads ◽  
Level Ice ◽  
Drift Direction

The reported presence of one third of remaining fossil reserves in the Arctic has sparked a lot of interest from energy companies. This has raised the necessity of developing specific engineering tools to design safely and accurately arctic-compliant offshore structures. The mooring system design of a turret-moored vessel in ice-infested waters is a clear example of such a key engineering tool. In the arctic region, a turret-moored vessel shall be designed to face many ice features: level ice, ice ridges or even icebergs. Regarding specifically level ice, a turret-moored vessel will tend to align her heading (to weather vane) with the ice sheet drift direction in order to decrease the mooring loads applied by this ice sheet. For a vessel already embedded in an ice sheet, a rapid change in the ice drift direction will suddenly increase the ice loads before the weathervaning occurs. This sudden increase in mooring loads may be a governing event for the turret-mooring system and should therefore be understood and simulated properly to ensure a safe design. The paper presents ADWICE (Advanced Weathervaning in ICE), an engineering tool dedicated to the calculation of the weathervaning of ship-shaped vessels in level ice. In ADWICE, the ice load formulation relies on the Croasdale model. Ice loads are calculated and applied to the vessel quasi-statically at each time step. The software also updates the hull waterline contour at each time step in order to calculate precisely the locations of contact between the hull and the ice sheet. Model tests of a turret-moored vessel have been performed in an ice basin. Validation of the simulated response is performed by comparison with model tests results in terms of weathervaning time, maximum mooring loads, and vessel motions.

Postglacial emergence of Amund and Ellef Ringnes islands, Nunavut: implications for the northwest sector of the Innuitian Ice Sheet

2004 ◽  
Vol 41 (3) ◽  
pp. 271-283 ◽  
Author(s):  
Nigel Atkinson ◽  
John England
Keyword(s):  
Late Holocene ◽  
Ice Sheet ◽  
The Arctic ◽  
Ice Flow ◽  
Geological Evidence ◽  
Level Curves ◽  
Ice Load ◽  
Holocene Transgression ◽  
Flow Features ◽  
Late Wisconsinan

This paper presents relative sea-level curves from Amund and Ellef Ringnes islands, northwest Queen Elizabeth Islands. These curves are of exponential form and record continuous, ongoing Holocene emergence, although northwest Ellef Ringnes Island is experiencing a late Holocene transgression. Isobases drawn on postglacial shorelines rise southeastward towards an uplift centre in Norwegian Bay. These suggest the Ringnes Islands occupied the northwest radius of the Innuitian uplift, which is congruent with glacial geological evidence suggesting parts of the Ringnes Islands were covered by the Late Wisconsinan Innuitian Ice Sheet. The isobases provide a provisional reconstruction of glacioisostatic recovery within the northwest Innuitian uplift. Their pattern supports earlier reconstructions that maximum Late Wisconsinan ice thickness occurred across Norwegian Bay, marking the position of an ice divide, which is consistent with ice-flow features on Amund Ringnes Island. They record the diminishing thickness of the Innuitian Ice Sheet from Norwegian Bay to the Arctic Ocean. The absence of an isobase embayment across the Ringnes Islands suggests a relatively uniform ice load across both islands and Hassel and Massey sounds. Parallel isobases across Peary Channel indicate this ice load extended beyond Massey Sound, although their northward deflection suggests an increasing influence of the former Axel Heiberg Island ice load.

Hydrodynamic Interaction of Ice Sheet and a Floating Platform

2016 ◽  
Author(s):  
Aziz Ahmed ◽  
Mohammed Abdul Hannan ◽  
Xudong Qian ◽  
Bai Wei
Keyword(s):  
Model Test ◽  
The Arctic ◽  
Wave Direction ◽  
Hydrodynamic Behavior ◽  
Incoming Wave ◽  
Hydrodynamic Analysis ◽  
Hydrodynamic Response ◽  
Level Ice ◽  
Ice Floes ◽  
Multi Body

Arctic is the one of the final frontiers in the field of oil and gas exploration. It is also a potential source of the vast amount of renewable energy using wind turbines and wave energy converters. Floating platforms hold certain advantages over fixed platforms for such harsh environment, as they allow disconnection and reconnection in the event of large icebergs or vast multi-year ice floes. They are also commercially attractive as they allow redeployment in other regions during the Arctic off-peak periods. However, such platforms will still need to encounter and withstand first-year level ice of varying sizes and from different directions. Such large ice floes will interfere with the hydrodynamic response of the floater. The hydrodynamic analysis of an isolated floater without accounting for the effect of the level ice is incomplete and may result in a un-conservative prediction of the floater’s response. The lack of any simple methodology to account for the effect of level ice on the hydrodynamic behavior of the floater is the motivation behind this study. This study aims to identify the most relevant parameters affecting the multi-body hydrodynamic behavior of level ice and a single floater. A standard semi-submersible represents the floater, and a range of geometric variations of the level ice simulates the varying nature of the ice environment encountered by the floaters in the Arctic. This study validates the hydrodynamic analysis procedure against model test on an ice floe and wave interaction. The calibration of the model test provides the damping coefficient required for the frequency domain, multi-body hydrodynamic model. This investigation varies the ice orientation and distance from the floater for a detailed parametric study employing the calibrated model. Current research finds that the presence of a comparably sized level ice floe near the floater significantly influences the hydrodynamic Response Amplitude Operator (RAO) of the floater. It can diminish the RAOs in some degree of freedom while enhancing the RAOs in other degree of freedoms. This study identifies the wave direction, ice floe distance, ice floe orientation as the most important parameters. Sway and pitch motion of the floater experienced the most enhancements due to the presence of level ice floe along the incoming wave direction. Additionally, this study proposes some initial upper bound values to account for the effect of level ice floes on the RAOs generated from a single body hydrodynamic analysis.

Numerical Simulation of Icebreaking Process and Parameters Sensitivity Analysis

2016 ◽  
Author(s):  
Yue Qiao ◽  
Duanfeng Han ◽  
Mange Teng ◽  
Guoliang Wang ◽  
Feng Liu
Keyword(s):  
Ice Sheet ◽  
Element Model ◽  
Total Force ◽  
Load History ◽  
Technological Support ◽  
Ice Load ◽  
Force Direction ◽  
The Impact ◽  
Ship Speed ◽  
Variation Tendency

The interdependence exists between ship response and ice load during the ship-ice interaction process. According to the ice properties and the velocity between a ship and ice can make influences on ice load, taking a Russian icebreaker as model, a series of numerical simulations were performed to research the ice load variation tendency rules in 3 axial directions and the total force direction. On the basis of regarding ice elements as elastic materials, the theory of a semi-infinite elastic plate resting on an elastic foundation was used to simulate ice sheet. By means of finite element model, stress and strain contours of typical moment and ice load history curve in four directions were obtained. Furthermore, the effect of important parameters such as elasticity modulus of ice, ice thickness and ship speed on the impact force were also analyzed. The results indicate that ice sheet will crack in the form of a circle centered on the collision point which accord with actual circumstance, and there are some certain variation relationships between each calculation parameters and ice load values. At the same time, the study can also provide technological support for ice load research.

scholarly journals Arctic warming induced by the Laurentide Ice Sheet topography

2018 ◽  
Vol 14 (6) ◽  
pp. 887-900 ◽  
Author(s):  
Johan Liakka ◽  
Marcus Lofverstrom
Keyword(s):  
Ice Sheets ◽  
Ice Sheet ◽  
Sheet Thickness ◽  
Temperature Response ◽  
Circulation Model ◽  
Ocean Model ◽  
The Arctic ◽  
Laurentide Ice Sheet ◽  
Stationary Waves ◽  
Continental Scale

Abstract. It is well known that ice sheet–climate feedbacks are essential for realistically simulating the spatiotemporal evolution of continental ice sheets over glacial–interglacial cycles. However, many of these feedbacks are dependent on the ice sheet thickness, which is poorly constrained by proxy data records. For example, height estimates of the Laurentide Ice Sheet (LIS) topography at the Last Glacial Maximum (LGM; ∼ 21 000 years ago) vary by more than 1 km among different ice sheet reconstructions. In order to better constrain the LIS elevation it is therefore important to understand how the mean climate is influenced by elevation discrepancies of this magnitude. Here we use an atmospheric circulation model coupled to a slab-ocean model to analyze the LGM surface temperature response to a broad range of LIS elevations (from 0 to over 4 km). We find that raising the LIS topography induces a widespread surface warming in the Arctic region, amounting to approximately 1.5 ∘C per km of elevation increase, or about 6.5 ∘C for the highest LIS. The warming is attributed to an increased poleward energy flux by atmospheric stationary waves, amplified by surface albedo and water vapor feedbacks, which account for about two-thirds of the total temperature response. These results suggest a strong feedback between continental-scale ice sheets and the Arctic temperatures that may help constrain LIS elevation estimates for the LGM and explain differences in ice distribution between the LGM and earlier glacial periods.

Ice load-bedrock uplift feedback leads to self-sustained oscillations in the Greenland Ice Sheet on long time scales

2020 ◽  
Author(s):  
Maria Zeitz ◽  
Jan Haacker ◽  
Ricarda Winkelmann
Keyword(s):  
Large Scale ◽  
Ice Sheet ◽  
Sheet Thickness ◽  
Greenland Ice Sheet ◽  
Partial Recovery ◽  
Positive Feedbacks ◽  
Linear Evolution ◽  
Ice Load ◽  
Sustained Oscillations ◽  
Long Time

<p>The Greenland ice sheet loses substantial amounts of mass, due to accelerating outlet glaciers and longer melting periods. Different positive feedback mechanisms, as the melt-elevation feedback and the ice-albedo feedback, introduce a non-linear evolution and may further accelerate mass loss. Negative feedbacks, such as the feedback between receding ice load and subsequent bedrock uplift, might counteract the accelerating positive feedbacks on long timescales. Roughly, the bedrock uplift amounts to 1/3 of the change in the ice sheet thickness on a timescale of millennia.</p><p>To explore the interplay of those feedbacks, we use simulations of the Greenland Ice Sheet with the Parallel Ice Sheet Model (PISM) including an Elastic Lithosphere Relaxing Asthenosphere (ELRA) model in an idealized warming scenario. In particular, we observe that depending on the temperature anomaly (and thus the retreat time) and the asthenosphere viscosity, three distinct responses of the ice sheet are possible:</p><ol><li>The full or partial retreat of the ice sheet.</li> <li>The full or partial recovery of the ice sheet after an initial retreat.</li> <li>Large-scale self-sustained oscillations of the volume of the ice sheet on multi-millennial timescales.</li> </ol>

Long-term ice loss from Greenland mediated by ice-load bedrock uplift feedback

2021 ◽  
Author(s):  
Maria Zeitz ◽  
Jan Haacker ◽  
Jonathan Donges ◽  
Ricarda Winkelmann
Keyword(s):  
Mass Loss ◽  
Large Scale ◽  
Ice Sheet ◽  
Sheet Thickness ◽  
Greenland Ice Sheet ◽  
Partial Recovery ◽  
Positive Feedbacks ◽  
Linear Evolution ◽  
Ice Load ◽  
Negative Feedbacks

<p>Mass loss from the Greenland Ice Sheet has significantly accelerated over the past decades, both through enhanced melting as well as the acceleration of outlet glaciers. Positive feedback mechanisms, including the melt-elevation feedback and the ice-albedo feedback, introduce a non- linear evolution and may further accelerate mass loss. Negative feedbacks, such as the feedback between receding ice load and subsequent bedrock uplift, might counteract these accelerating positive feedbacks on long timescales. Bedrock uplift can amount to roughly one third of the change in the ice sheet thickness on a timescale of millennia. Here we explore the interplay of both positive and negative feedbacks, using simulations of the Greenland Ice Sheet with the Parallel Ice Sheet Model (PISM) including an Elastic Lithosphere Relaxing Asthenosphere (ELRA) model in an idealized warming scenario. In particular, we find that depending on the temperature anomaly (and thus the ice retreat rate) and the asthenosphere viscosity, distinct responses of the ice sheet are possible, ranging from the full or partial retreat of the ice sheet to the full or partial recovery of the ice sheet after an initial retreat, and potential large-scale self-sustained oscillations of ice volume on multi- millennial timescales.</p>

scholarly journals Arctic warming induced by the Laurentide ice sheet topography

2018 ◽  
Author(s):  
Johan Liakka ◽  
Marcus Lofverstrom
Keyword(s):  
Ice Sheet ◽  
Sheet Thickness ◽  
Temperature Response ◽  
Arctic Region ◽  
Atmospheric Model ◽  
Ocean Model ◽  
The Arctic ◽  
Laurentide Ice Sheet ◽  
Stationary Waves ◽  
Continental Scale

Abstract. It is well known that ice sheet-climate feedbacks are essential for realistically simulating the spatio-temporal evolution of continental ice sheet over glacial-interglacial cycles. However, many of these feedbacks are dependent on the ice sheet thickness, which is poorly constrained by proxy data records. For example, height estimates of the Laurentide Ice Sheet (LIS) topography at the Last Glacial Maximum (LGM; ~ 21,000 years ago) vary by more than 1 km between different ice-sheet reconstructions. In order to better constrain the LIS elevation it is therefore important to understand how the mean climate is influenced by elevation discrepancies of this magnitude. Here we use an atmospheric model coupled to a slab-ocean model to analyze the LGM surface temperature response to a broad range of LIS elevations (from 0 to over 4 km). We find that raising the LIS topography induces a widespread surface warming in the Arctic region, amounting to approximately 1.5 °C per km elevation increase, or about 6.5 °C for the highest LIS. The warming is attributed to an increased northward energy flux by atmospheric stationary waves, reinforced by surface albedo and water vapor feedbacks, which account for about two-thirds of the total temperature response. These results suggest a positive feedback between continental-scale ice sheets and the Arctic temperatures that may help constrain LIS elevation estimates for the LGM and explain differences in ice distribution between the LGM and earlier glacial periods.

Consideration of Geopolitical Challenges within the Analysis of Geoenvironmental Risks for Oil and Gas Development of the Russian Arctic

2019 ◽  
Vol 16 (6) ◽  
pp. 50-59
Author(s):  
O. P. Trubitsina ◽  
V. N. Bashkin
Keyword(s):  
Oil And Gas ◽  
Oil And Gas Industry ◽  
Optimal Operation ◽  
The Arctic ◽  
Stage Model ◽  
Oil And Gas Development ◽  
Gas Industry ◽  
The Impact ◽  
Further Development ◽  
Geopolitical Risks

The article is devoted to the consideration of geopolitical challenges for the analysis of geoenvironmental risks (GERs) in the hydrocarbon development of the Arctic territory. Geopolitical risks (GPRs), like GERs, can be transformed into opposite external environment factors of oil and gas industry facilities in the form of additional opportunities or threats, which the authors identify in detail for each type of risk. This is necessary for further development of methodological base of expert methods for GER management in the context of the implementational proposed two-stage model of the GER analysis taking to account GPR for the improvement of effectiveness making decisions to ensure optimal operation of the facility oil and gas industry and minimize the impact on the environment in the geopolitical conditions of the Arctic.The authors declare no conflict of interest

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