Station-Keeping Trials in Ice: Ice and Metocean Conditions

2018 ◽  
Author(s):  
Sigurd Henrik Teigen ◽  
Joakim K. Lindvall ◽  
Ilija Samardzija ◽  
Roar I. Hansen
Keyword(s):  
Spatial Data ◽  
Ice Core ◽  
Ocean Current ◽  
Ice Thickness ◽  
Physical Parameters ◽  
Station Keeping ◽  
Sea Bed ◽  
Ice Drift ◽  
Ice Conditions ◽  
Drifting Ice

In March 2017, Statoil performed station-keeping trials in drifting ice in the Bay of Bothnia with the two anchor handling tug supply vessels Magne Viking and Tor Viking. During the trials observations of ice and metocean conditions were performed via a range of platforms and techniques. The purpose of the observations was to document the main physical parameters affecting the station-keeping vessel and ice management vessel, as well as giving tactical information on ice conditions and input to simultaneous numerical simulations. Measurements of meteorological parameters (wind speed, wind direction, air temperature, etc.) were done from the two vessels and supplemented with manual observations. Ice drift was independently measured by drifting ice trackers and ADCPs (also measuring ocean current) moored on the sea bed. Measurements of ice thickness were carried out with moored Ice Profiling Sensors (IPSs) and manual ice core samples, which were also analyzed for salinity and temperature profiles. The IPS ice thickness data was later processed together with the ice drift to provide 2D spatial data. The deepest ice ridge keels ranged from 5.4 m at the site with the most benign ice conditions to 10.9 m at the most severe site. Ridge frequency also increased from 2 ridges km−1 to 16 ridges km−1 at the most severe site (given a keel threshold of 3 m). In the present study, statistical summaries of the different time series collected at the sites of the station-keeping trials are presented, highlighting the variability in the ice conditions. Using the vessel tracks and overall drift of the broken channels, ice thickness and drift measurements are classified as being inside or outside the managed ice zone.

Analysis of tidal sea-ice movement using a drifting ice beacon array in the Barents Sea

2020 ◽  
Author(s):  
Amey Vasulkar ◽  
Lars Kaleschke ◽  
Martin Verlaan ◽  
Cornelis Slobbe
Keyword(s):  
Sea Ice ◽  
Barents Sea ◽  
Global Ocean ◽  
Series Data ◽  
Small Scale ◽  
Ice Thickness ◽  
Drag Coefficients ◽  
The Barents Sea ◽  
Ice Drift ◽  
Drifting Ice

<p>In an experiment to validate an ice forecast and route optimization system, an array of 15 ice drift beacons/buoys were deployed between Edgeøya and Kong Karls Land in the east of Svalbard to measure the sea ice movement. These beacons recorded data at a sampling frequency of 15 minutes in the duration from March 2014 to May 2014 with different start and end dates based on their life. The particularly short time step captures the small scale effect of tides on the drifting ice. In this region of the Barents Sea, the frequency of the inertial motion is very close to the M2 tidal frequency. Hence, it is not possible to extract the tidal motion from the time series data of the buoys by using a Fourier analysis. It is also likely that these effects will interact. Instead, we develop a physics-based <em>free drift</em> ice model that can simulate the drift at all tidal and other frequencies.</p><p>The model is forced by winds obtained from the ERA5 Reanalysis dataset of ECMWF and ocean currents obtained from the Global Ocean Analysis product of CMEMS. Due to the effect of tides, the model is also forced by the tides obtained from the Global Tide and Surge Model (GTSM v3.0) which is built upon Delft3D-FM unstructured mesh code. This free drift model is validated against 8 of the 15 beacon trajectories. The model along with the observed data can be then be used to obtain insights on the relationship between the sea ice velocities and the tides. This will be particularly useful to obtain the effect of ice drift on tides in tidal models.</p><p>The model uncertainty is mainly due to oceanic and atmospheric drag coefficients, C<sub>dw</sub> and C<sub>da</sub>, respectively, and the sea ice thickness, h<sub>i</sub>. This study also focuses on optimizing the ratio of drag coefficients (C<sub>dw</sub>/C<sub>da</sub>) for the different beacon trajectories while varying the ice thickness between 0.1 m - 1.5 m and the ice-air drag coefficient between (0.5-2.5)x10<sup>-3</sup>. This ratio facilitates the evaluation of the frictional drag between the ice-water interface and thus, helps in determining the effect of ice on tides in tidal models.</p>

Station-Keeping Trials in Ice: Overview of Ice Management Support

2018 ◽  
Author(s):  
Mike Neville ◽  
Erik Almkvist ◽  
Francesco Scibilia ◽  
Joakim K. Lindvall ◽  
Pavel Liferov
Keyword(s):  
Management Support ◽  
Station Keeping ◽  
Target Condition ◽  
Management Software ◽  
Sole Purpose ◽  
Planning Phase ◽  
Ice Conditions ◽  
Drifting Ice

In March 2017, Statoil performed station-keeping trials in drifting ice in the Bay of Bothnia. The anchor handling tug supply vessel Magne Viking, performed station keeping operations in various ice conditions, including managed and non-managed ice. Physical ice management was used to manage the approaching ice to a target condition suitable for the station keeping tests, and to enable other essential operations including deployment and retrieval of the mooring spread and other equipment. Given the objective of the trials, physical ice management activities were performed in such a way to allow investigation of various relevant parameters that influence the managed ice condition. Additional tests were also performed for the sole purpose to assist with validation of Aker Arctic’s ice management software “AIMS”, including tests designed to estimate the performance of the vessels under different ice conditions. This paper focuses on the physical ice management operations performed by the ice management vessel Tor Viking (TV) during the Station Keeping Trials in ice (SKT). Also included is a discussion on how AIMS was used in the planning phase and how simulations compared with actual observations.

Station-Keeping Trials in Ice: Numerical Modelling

2018 ◽  
Author(s):  
Nicolas Serre ◽  
Sofien Kerkeni ◽  
Dmitry Sapelnikov ◽  
Cyrille Akuetevi ◽  
Sergiy Sukhorukov ◽  
...  
Keyword(s):  
Data Collection ◽  
Numerical Modelling ◽  
Numerical Simulations ◽  
Single Point ◽  
Station Keeping ◽  
Broken Ice ◽  
Ice Conditions ◽  
Drifting Ice

In March 2017, Statoil performed station-keeping trials in drifting ice in the Bay of Bothnia with two anchor handling supply vessels; Magne Viking and Tor Viking. The data collection included monitoring of ice conditions and response of Magne Viking during ice interaction events. The present paper describes numerical simulations of broken ice and intact ice interaction events with single point moored Magne Viking.

Station-Keeping Trials in Ice: Dynamic Positioning in Ice — Results and Learnings

2018 ◽  
Author(s):  
Sofien Kerkeni ◽  
Pavel Liferov ◽  
Nicolas Serré ◽  
Robert Bridges ◽  
Finn Jorgensen
Keyword(s):  
Full Scale ◽  
Control Algorithms ◽  
Dynamic Positioning ◽  
Station Keeping ◽  
Positioning Systems ◽  
Ice Conditions ◽  
Drifting Ice ◽  
External Loads

Dynamic Positioning Systems are used in numerous types of marine operations. Due to the important differences in the external loads acting on the vessel, standard DP systems may fail to perform in ice conditions. Moreover, specific principles and position keeping philosophies should be applied in ice covered waters. The objective of the paper is to elaborate on these aspects by presenting and analyzing full scale DP tests. These tests were a part of the station-keeping trials performed in March 2017 in drifting ice in the Bay of Bothnia. Control algorithms limitations of Standard DP Systems are presented, showing the necessity of new control principles. The importance of crew training is also demonstrated along with the approaches to keep position in ice.

DP Ice Model Test of Arctic Drillship and Polar Research Vessel

2012 ◽  
Author(s):  
Torbjørn Hals ◽  
Nils Albert Jenssen
Keyword(s):  
Numerical Models ◽  
Offshore Structures ◽  
Model Tests ◽  
Full Scale ◽  
The Arctic ◽  
Research Vessel ◽  
Station Keeping ◽  
Ice Drift ◽  
Ice Conditions ◽  
Ice Model

The paper presents the results from a series of ice model tests performed as part of the DYPIC (Dynamic Positioning in Ice Conditions) research program. DYPIC is a research and development project within the EU’s ERA NET MARTEC project. The major purpose of the DYPIC project is development of equipment and methods for DP Ice Model testing which allows the prediction of station keeping capability of different vessel types and offshore structures under various ice conditions. The first DYPIC model tests performed in 2011 was conducted with two significantly different vessel sizes, a 68.0000 m3 volume displacement arctic drillship and an 8.600 m3 polar research vessel. The model scale was 1/30 for the arctic drillship and 1/18.6 for the Polar Research Vessel. The model tests were performed in the ice model basin at HSVA using vessel models equipped with thruster capacity similar to full scale operation according to DP class 2 / 3 operations. The DP control system was also modified from normal open water DP operations in order to cope with the highly varying ice drift loads acting on the vessel. The test program gave data supporting the development of numerical models of ice loads from managed ice, see reference [6]. The main focus in this paper is on the station keeping performance and associated thrust utilization as a function of varying ice drift loads. The results and data collected in the first year of the DYPIC program demonstrates that DP ice model tests will be a valuable tool for evaluation of vessel performance prior to moving on to full scale arctic DP operations.

A Scalable Framework for Process-Aware Thermal Simulation of Additive Manufacturing Processes

2021 ◽  
pp. 1-16
Author(s):  
Yaqi Zhang ◽  
Vadim Shapiro ◽  
Paul Witherell
Keyword(s):  
Additive Manufacturing ◽  
Heat Source ◽  
Spatial Data ◽  
Manufacturing Process ◽  
Thermal Simulation ◽  
Physical Parameters ◽  
Moving Heat Source ◽  
Time Step ◽  
Fused Deposition ◽  
Am Processes

Abstract Many additive manufacturing (AM) processes are driven by a moving heat source. Thermal field evolution during the manufacturing process plays an important role in determining both geometric and mechanical properties of the fabricated parts. Thermal simulation of AM processes is challenging due to the geometric complexity of the manufacturing process and inherent computational complexity that requires a numerical solution at every time increment of the process. We propose a new general computational framework that supports scalable thermal simulation at path scale of any AM process driven by a moving heat source. The proposed framework has three novel ingredients. First, the path-level discretization is process-aware, which is based on the manufacturing primitives described by the scan path and the thermal model is formulated directly in terms of manufacturing primitives. Second, a spatial data structure, called contact graph, is used to represent the discretized domain and capture all possible thermal interactions during the simulation. Finally, the simulation is localized based on specific physical parameters of the manufacturing process, requiring at most a constant number of updates at each time step. The latter implies that the constructed simulation not only scales to handle three-dimensional (3D) printed components of arbitrary complexity but also can achieve real-time performance. To demonstrate the efficacy and generality of the framework, it has been successfully applied to build thermal simulations of two different AM processes, fused deposition modeling (FDM) and powder bed fusion (PBF).

Arctic Offshore Loading Downtime Due to Variability in Ice Drift Direction

2005 ◽  
Vol 59 (1) ◽  
pp. 9-26
Author(s):  
Basile Bonnemaire
Keyword(s):  
Risk Analysis ◽  
Ice Drift ◽  
Ice Conditions ◽  
Qualitative Risk Analysis ◽  
Drift Direction

Four arctic offshore loading concepts are selected, loading from the corner of a platform, loading in the wake of a loading tower, Submerged Turret Loading (STL) and Single Anchor Loading (SAL). The influence of variations in the ice drift direction on the performance of these concepts is discussed and critical drift events are determined. Ice drift measurements from eight ARGOS/GPS buoys deployed in the Pechora Sea in winters 1995 and 1998 are analysed to estimate downtime rates of these loading systems due to ice drift heading changes. Depending on the location in the Pechora Sea and the chosen concept, downtime rates range from 6 to 72%. A discussion on how these rates will vary with different assumptions, different ice conditions or different ice management is given. Finally the loading concepts are compared through a qualitative risk analysis.

scholarly journals Airborne River-Ice Thickness Profiling with Helicopter-Borne UHF Short-Pulse Radar

1987 ◽  
Vol 33 (115) ◽  
pp. 330-340 ◽  
Author(s):  
Steven A Arcone ◽  
Allan J Delaney
Keyword(s):  
Short Pulse ◽  
Hanging Wall ◽  
Open Water ◽  
High Water ◽  
High Water Content ◽  
Ice Thickness ◽  
Frazil Ice ◽  
Pulse Radar ◽  
Detailed Surface ◽  
Ice Conditions

AbstractThe ice-thickness profiling performance of a helicopter-mounted short-pulse radar operating at approximate center frequencies of 600 and 900 MHz was assessed. The antenna packages were mounted 1.2 m off the skid of a small helicopter whose speed and altitude were varied from about 1.8 to 9 m/s and 3 to 12 m. Clutter from the helicopter offered minimal interference with the ice data. Data were acquired in Alaska over lakes (as a proving exercise) and two rivers, whose conditions varied from open water to over 1.5 m of solid ice with numerous frazil-ice formations. The most readily interpretable data were acquired when the ice or snow surface was smooth. Detailed surface investigations on the Tanana River revealed good correlations of echo delay with solid ice depth, but an insensitivity to frazil-ice depth due to its high water content. On the Yukon River, coinciding temporally coherent surface and bottom reflections were associated with solid ice and smooth surfaces. All cases of incoherent surface returns (scatter) occurred over ice rubble. Rough-surface scattering was always followed by the appearance of bottom scattering but, in many cases, including a hanging-wall formation of solid frazil ice, bottom scattering occurred beneath coherent, smooth-surface reflections. Areas of incoherent bottom scattering investigated by drilling revealed highly variable ice conditions, including frazil ice. The minimum ice thickness that could be resolved from the raw data was about 0.2 m with the 600 MHz antenna and less than 0.15 m with the 900 MHz antenna.

scholarly journals Estimating the Speed of Icegoing Ships by Integrating SAR Imagery and Ship Data From Automatic Identification System

2018 ◽  
Author(s):  
Markku Simila ◽  
Mikko Lensu
Keyword(s):  
Mean Squared Error ◽  
Automatic Identification ◽  
Identification System ◽  
Automatic Identification System ◽  
Squared Error ◽  
Ice Drift ◽  
Gulf Of Bothnia ◽  
Ice Conditions ◽  
Time Gap ◽  
Sar Imagery

Ship speeds extracted from AIS data vary with ice conditions. We extrapolated this variation with SAR data to a chart of expected icegoing speed. The study is for the Gulf of Bothnia in March 2013 and for ships with ice class 1A Super that are able to navigate without icbreaker assistance. The speed was normalized to 0-10 for each ship. As the matching between AIS and SAR was complicated by ice drift during the time gap, from hours to two days, we calculated a set of local SAR statistics over several scales. We used random tree regression to estimate the speed. The accuracy was quantified by mean squared error (MSE), and the fraction of estimates close to the actual speeds. These depended strongly on the route and the day. MSE varied from 0.4 to 2.7 units2 for daily routes. 65 % of the estimates deviated less than one unit and 82 % less than 1.5 units from the AIS speeds. The estimated daily mean speeds were close to the observations. Largest speed decreases were provided by the estimator in a dampened form or not at all. This improved when ice chart thickness was included as one predictor.

scholarly journals Sea-ice drift characteristics revealed by measurement of acoustic Doppler current profiler and ice-profiling sonar off Hokkaido in the Sea of Okhotsk

2011 ◽  
Vol 52 (57) ◽  
pp. 1-8 ◽  
Author(s):  
Yasushi Fukamachi ◽  
Kay I. Ohshima ◽  
Yuji Mukai ◽  
Genta Mizuta ◽  
Masaaki Wakatsuchi
Keyword(s):  
Sea Ice ◽  
Sea Of Okhotsk ◽  
Acoustic Doppler Current Profiler ◽  
Ice Thickness ◽  
Coastal Station ◽  
Turning Angle ◽  
The Sea Of Okhotsk ◽  
Ice Drift ◽  
Current Profiler ◽  
Sea Ice Drift

AbstractIn the southwestern part of the Sea of Okhotsk off Hokkaido, sea-ice drift characteristics are investigated using the ice and water velocities obtained from a moored upward-looking acoustic Doppler current profiler (ADCP) during the winters of 1999–2001. Using hourly-mean values of these data along with the wind data measured at a nearby coastal station, the wind factor and turning angle of the relative velocity between the ice and water velocities with respect to the wind are calculated assuming free drift under various conditions. Since the simultaneous sea-ice draft data are also available from a moored ice-profiling sonar (IPS), we examine the dependence of drift characteristics on ice thickness for the first time. As ice thickness increases and wind decreases, the wind factor decreases and the turning angle increases, as predicted by the theory of free drift. This study clearly shows the utility of the moored ADCP measurement for studying sea-ice drift, especially with the simultaneous IPS measurement for ice thickness, which cannot be obtained by other methods.

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