scholarly journals Glacier calving: a numerical model of forces in the calving-speed/water-depth relation

2000 ◽  
Vol 46 (153) ◽  
pp. 188-196 ◽  
Author(s):  
Brian Hanson ◽  
Roger LeB. Hooke
Keyword(s):  
Numerical Model ◽  
Numerical Modelling ◽  
Water Depth ◽  
Empirical Data ◽  
Bending Moments ◽  
Physical Explanation ◽  
Differential Flow ◽  
Calving Rate ◽  
Deviatoric Stresses

AbstractEmpirical data suggest that the rate of calving of grounded glaciers terminating in water is directly proportional to the water depth. Important controls on calving may be the extent to which a calving face tends to become oversteepened by differential flow within the ice and the extent to which bending moments promote extrusion and bottom crevassing at the base of a calving face. Numerical modelling suggests that the tendency to become oversteepened increases roughly linearly with water depth. In addition, extending longitudinal deviatoric stresses at the base of a calving face increase with water depth. These processes provide a possible physical explanation for the observed calving-rate/water-depth relation.

Hybrid Verification of a Deepwater FPSO Using Truncated Model Tests and Numerical Simulations

2021 ◽  
Author(s):  
Xiangbo Liu ◽  
Ching Theng Liong ◽  
Nitesh Kumar ◽  
Kie Hian Chua ◽  
Allan Ross Magee ◽  
...  
Keyword(s):  
Numerical Model ◽  
Numerical Modelling ◽  
Water Depth ◽  
Return Period ◽  
Line Length ◽  
Model Tests ◽  
Mooring Line ◽  
Mooring System ◽  
Test Results ◽  
Set Up

Abstract This paper presents verification of a deep water FPSO with a semi-taut mooring system using model tests and numerical modelling commonly referred to as the hybrid method. The vessel under investigation is a FPSO of 310m in length and 47m in beam with an internal turret mooring system of 12 lines in 2000m water depth. Two configurations of the mooring systems i.e. inline and bisecting are investigated for sea-states up to 1000yr return period. A full depth mooring system has been developed for the FPSO and model tests will be carried out to verify the model. Due to limitations to the size of the model basins, the model tests will be carried out for a truncated mooring setup. Non-linear horizontal stiffness of a single mooring line and the complete mooring system with truncation is compared to that of the existing full depth mooring system. Discrepancies in the vertical forces due to truncation of line length will be discussed in the paper. A numerical model of the truncated set-up will be calibrated using model test results.

scholarly journals THE USE OF ARRAY PROCESSORS FOR NUMERICAL MODELLING OF TIDAL ESTUARY DYNAMICS

1980 ◽  
Vol 1 (17) ◽  
pp. 142
Author(s):  
D. Prandle ◽  
E.R. Funke ◽  
N.L. Crookshank ◽  
R. Renner
Keyword(s):  
Numerical Model ◽  
Numerical Modelling ◽  
Hybrid Model ◽  
Numerical Models ◽  
Computer Time ◽  
Scale Model ◽  
Hybrid Modelling ◽  
Tidal Propagation ◽  
Physical Scale ◽  
Array Processors

The use of array processors for the numerical modelling of estuarine systems is discussed here in the context of "hybrid modelling", however, it is shown that array processors may be used to advantage in independent numerical simulations. Hybrid modelling of tidal estuaries was first introduced by fiolz (1977) and later by Funke and Crookshank (1978). In a hybrid model, tidal propagation in an estuary is simulated by dynamically linking an hydraulic (or physical) scale model of part of the estuary to a numerical model of the remaining part in a manner such that a free interchange of flow occurs at the interface(s). Typically, the elevation of the water surface at the boundary of the scale model is measured and transmitted to the numerical model. In return, the flow computed at the boundary of the numerical model is fed directly into the scale model. This approach enables the extent of the scale model to be limited to the area of immediate interest (or to that area where flow conditions are such that they can be most accurately simulated by a scale model). In addition, since the region simulated by the numerical model can be extended almost indefinitely, the problems of spurious reflections from downstream boundaries can be eliminated. In normal use, numerical models are evaluated on the basis of computing requirements, cost and accuracy. The computer time required to simulate one tide cycle is, in itself, seldom of interest except in so far as it affects the above criteria. However in hybrid modelling this parameter is often paramount since concurrent operation of the numerical and scale models requires that the former must keep pace with the latter. The earlier hybrid model of the St. Lawrence (Funke and Crookshank, 1978) involved a one-dimensional numerical model of the upstream regions of the river. However, future applications are likely to involve extensive two-dimensional numerical simulation.

scholarly journals Modeling the transport of radioactive pollution in the Ussuri Gulf during the first days after the nuclear accident in the Chazhma Bay in August 1985

2020 ◽  
Author(s):  
П.А. ФАЙМАН ◽  
М.В. БУДЯНСКИЙ ◽  
М.Ю. УЛЕЙСКИЙ ◽  
С.В. ПРАНЦ ◽  
В.Л. ВЫСОЦКИЙ ◽  
...  
Keyword(s):  
Numerical Model ◽  
Coherent Structures ◽  
Empirical Data ◽  
Radioactive Fallout ◽  
Sea Surface ◽  
Radioactive Pollution ◽  
Nuclear Submarine ◽  
The North ◽  
Lagrangian Modeling ◽  
Hyperbolic Points

Представлены результаты лагранжевого моделирования распространения радиоактивного загрязнения в Уссурийском заливе на различных горизонтах по глубине на основе численной региональной модели циркуляции ROMS с использованием эмпирических данных выпадения радиоактивных осадков из атмосферы на поверхность акватории в день аварии на атомной подводной лодке в бухте Чажма 10 августа 1985 г. Показано, что радиоактивное пятно могло оставаться в Уссурийском заливе в течение первых четырех суток после аварии. Установлено, что эволюция и деформация начального пятна загрязнения на разных горизонтах обусловлены влиянием вихрей разных полярностей и размеров (мезомасштабный циклон в центре залива, субмезомасштабный антициклон на севере и мезомасштабный антициклон на юге) и лагранжевых когерентных структур, связанных с гиперболическими точками в заливе. The results of Lagrangian modeling of the transport of radioactive pollution in the Ussuri Gulf at various depths based on a regional ROMS numerical model of circulation using the empirical data on the radioactive fallout from the atmosphere at the sea surface on the day of the accident at a nuclear submarine in the Chazhma Bay in August 10, 1985. It was shown that the radioactive particles remain in the Ussuri Gulf for the first 4 days after the accident. It has been shown that the evolution and deformation of the initial pollution patch on various horizons was influenced by vortices of different polarity and size in the Ussuri Gulf (a mesoscale cyclone in the center of the Gulf, a sub-mesoscale anticyclone in the north and a mesoscale anticyclone in the south) and by Lagrangian coherent structures connected with hyperbolic points in the Gulf.

scholarly journals Numerical modelling of agglomeration process in a granular bed containing melting particles

2021 ◽  
Vol 2057 (1) ◽  
pp. 012063
Author(s):  
I G Donskoy
Keyword(s):  
Thermal Decomposition ◽  
Porous Medium ◽  
Numerical Model ◽  
Numerical Modelling ◽  
Side Wall ◽  
Low Grade ◽  
Granular Bed ◽  
Agglomeration Process ◽  
Simulation Results ◽  
Implicit Numerical Method

Abstract The paper considers a numerical model of a flow in a porous medium containing particles of a melting component (polymer). For this, an implicit numerical method of splitting in directions is used. Calculations are carried out for two heating methods (through the side wall, or by the input gas). The simulation results qualitatively reproduce some of the experimentally observed features of the thermal decomposition of polymer-containing mixtures. The results obtained are of interest in the study of low-grade fuels processing, often accompanied by agglomeration, as well as in the development of methods by which agglomeration can be prevented.

scholarly journals A unifying framework for iceberg-calving models

2010 ◽  
Vol 56 (199) ◽  
pp. 822-830 ◽  
Author(s):  
Jason M. Amundson ◽  
Martin Truffer
Keyword(s):  
Empirical Relationship ◽  
Ice Thickness ◽  
Ice Shelf ◽  
Physical Explanation ◽  
Positive Feedbacks ◽  
First Order ◽  
External Forcings ◽  
Iceberg Calving ◽  
Calving Rate ◽  
Glacier Flow

AbstractWe propose a general framework for iceberg-calving models that can be applied to any calving margin. The framework is based on mass continuity, the assumption that calving rate and terminus velocity are not independent and the simple idea that terminus thickness following a calving event is larger than terminus thickness at the event onset. The theoretical, near steady-state analysis used to support and analyze the framework indicates that calving rate is governed, to first order, by ice thickness, thickness gradient, strain rate, mass-balance rate and backwards melting of the terminus; the analysis furthermore provides a physical explanation for a previously derived empirical relationship for ice-shelf calving (Alley and others, 2008). In the calving framework the pre- and post-calving terminus thicknesses are given by two unknown but related functions. The functions can vary independently of changes in glacier flow and geometry, and can therefore account for variations in calving behavior due to external forcings and/or self-sustaining calving processes (positive feedbacks). Although the calving framework does not constitute a complete calving model, any thickness-based calving criterion can easily be incorporated into the framework. The framework should be viewed as a guide for future attempts to parameterize calving.

Validation of a Numerical Model for the Investigation of Tension Leg Platforms With Marine Energy Application Using REEF3D

2021 ◽  
Author(s):  
Christian Windt ◽  
Nils Goseberg ◽  
Tobias Martin ◽  
Hans Bihs
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Numerical Model ◽  
Numerical Modelling ◽  
Numerical Data ◽  
Wave Structure ◽  
Offshore Wind ◽  
High Resolution Data ◽  
Marine Energy ◽  
Mooring Dynamics

Abstract Exploiting the offshore wind resources using floating offshore wind systems at sites with deep water depths requires advanced knowledge of the system behaviour, including the hydro-, areo-, and mooring dynamics. To that end, high-fidelity numerical modelling tools, based on Computational Fluid Dynamics, can support the research and development of floating offshore wind systems by providing high-resolution data sets. This paper presents the first steps towards the numerical modelling of tension leg platforms for floating offshore wind applications using the open-source Computational Fluid Dynamics toolbox REEF3D. The numerical model of a taut-moored structure is validated against experimental reference data. Results from wave-only test cases highlight the simplicity and effectiveness of the wave generation method, implemented in REEF3D. For the considered wave-structure interaction cases, deviations between the experimental and numerical data can be observed for the surge and pitch displacements, while the heave displacement and the mooring forces are capture with sufficient accuracy. Overall, the numerical results indicate high potential of REEF3D to be used for the modelling of floating offshore wind systems.

Physical and numerical modelling of sediment guiding walls in an alpine river

2021 ◽  
Author(s):  
Jakob Siedersleben ◽  
Marco Schuster ◽  
Dennis Ties ◽  
Benjamin Zwick ◽  
Markus Aufleger ◽  
...  
Keyword(s):  
Numerical Model ◽  
Numerical Modelling ◽  
Power Plants ◽  
Sediment Management ◽  
Design Flow ◽  
Scale Model ◽  
Surface Measurement ◽  
Management Options ◽  
Erosion And Deposition ◽  
Alpine River

<p>The presented work is part of the optimization of the sediment management at the hydroelectric powerplants in Reutte/Höfen in Austria. The weirs of the two powerplants are situated at the alpine river Lech, located about 3 km upstream of the Lechaschau gauge (A=1012.2 km²). Totally five sluice gates and a fixed overflow weir are controlling the upstream reservoir, being subjected to high rates of coarse bed load material. In frame of a coupled approach of physical and numerical modelling, different options to (i) avoid/minimize sediment deposition and (ii) allow improved sediment flushing were tested and optimized. Besides a lowering of energy losses (reduced spilling times) the reduction of depositions downstream close to the turbine outlet were considered.</p><p>The physical model covers the hydropower and weir system of both power plants within a stretch of 400m / 150m using a model scale of 1:25. Investigated situations covered periods of reservoir sedimentation, flushing of the reservoir and typical flood flow situations (e.g. HQ1 and an unsteady HQ5 event). For model parametrization, sediment samples to quantify size distribution were taken in the field. Sediment inputs to the model were realized dynamically and were required (due to scaling effects) to exclude cohesive fractions having a minimum particle size of 0.5 mm. The full-area surface measurement of the river bed was made by means of airborne laser bathymetry and echo sounding.</p><p>As part of an optimization of the overall sediment management strategy, the focus of the presented research is on the western located runoff power plant Höfen. Via a lateral water intake, a maximum design flow of 15 m³/s is withdrawn causing that the intake structure is subjected to sediment depositions. Within the described scale model (1:25) and a partial scale model (1:15) covering the western side, several management options and configurations of sediment guiding walls were tested. Erosion and deposition as well as the transported material are assessed by 3D laser scanning and permanent monitoring of transported sediment load entering and leaving the scale model.</p><p>Complementary, a 2D hydro numerical model using a layer based multi fraction approach for sediment transport is set up for an extended area to simulate the morpho-dynamic behavior. The numerical model covers the whole weir system and 750 m of the upstream part of the Lech. The simulations made were realized at nature scale and allowed to mimic the erosion and deposition pattern obtained within the physical modelling for different tested options. Regardless of a chosen guiding wall setup, the results showed that each one is compromise between sediment defense and the effectiveness of the subsequent flushing processes.</p>

In-Situ Static and Dynamic Testing and Numerical Modelling of the Dome of the Siena Cathedral (Italy)

2015 ◽  
pp. 85-114
Author(s):  
Gianni Bartoli ◽  
Michele Betti ◽  
Saverio Giordano ◽  
Maurizio Orlando
Keyword(s):  
Numerical Model ◽  
Numerical Modelling ◽  
13Th Century ◽  
Structural Behaviour ◽  
Destructive Testing ◽  
Dynamic Vibration ◽  
Heritage Buildings ◽  
Siena Cathedral ◽  
Vibration Tests

The chapter reports on the in-situ experimental campaign and the numerical modelling that were performed to assess the static and dynamic behaviour of the Cupola of the Siena Cathedral in Italy: an irregular polygonal masonry structure built in the 13th century and composed of two domes. The research was motivated by the failure of some of the stone-trusses which connect the two masonry domes and consists of: a) single and double flat-jack tests in the internal dome, b) dynamic vibration tests on the Cupola under environmental (wind) and artificial (vibrodyne) loads and c) dynamic vibration tests on the double colonnade located below the Cupola (hammer impact tests). Results of tests were employed to identify a numerical model of the Cupola, which allowed to simulate its structural behaviour and to account for the failure of the stone-trusses between the two domes. The numerical model was later extended to the whole Cathedral. Through the discussion of an emblematic case study, the chapter shows a careful application of non-destructive testing (NDT) and numerical modelling in the field of assessment (and rehabilitation) of heritage buildings.

Fronts and shelf-circulation models

1981 ◽  
Vol 302 (1472) ◽  
pp. 597-604 ◽  
Keyword(s):  
Numerical Model ◽  
Numerical Modelling ◽  
Continental Shelf ◽  
Satellite Imagery ◽  
Three Dimensional ◽  
Shelf Circulation ◽  
Eddy Formation ◽  
Coastal Front

Satellite imagery shows that fronts and frontal eddies are widespread on the northwest European continental shelf. The implications for the numerical modelling of transports (for example, of pollutants) are discussed. A brief review of some models of shelf circulation is given. It is argued that to include fronts in models of shelf circulation requires a better understanding of dynamics on the frontal scale. A three-dimensional numerical model of eddy formation in a coastal front is then presented that reproduces many of the observed features.

scholarly journals Testing the effect of water in crevasses on a physically based calving model

2012 ◽  
Vol 53 (60) ◽  
pp. 90-96 ◽  
Author(s):  
S. Cook ◽  
T. Zwinger ◽  
I.C. Rutt ◽  
S. O'Neel ◽  
T. Murray
Keyword(s):  
Finite Element ◽  
Water Depth ◽  
Surface Mass Balance ◽  
Two Dimensional ◽  
Finite Element Code ◽  
Surface Mass ◽  
Starting Point ◽  
Physically Based ◽  
Calving Rate

AbstractA new implementation of a calving model, using the finite-element code Elmer, is presented and used to investigate the effects of surface water within crevasses on calving rate. For this work, we use a two-dimensional flowline model of Columbia Glacier, Alaska. Using the glacier’s 1993 geometry as a starting point, we apply a crevasse-depth calving criterion, which predicts calving at the location where surface crevasses cross the waterline. Crevasse depth is calculated using the Nye formulation. We find that calving rate in such a regime is highly dependent on the depth of water in surface crevasses, with a change of just a few metres in water depth causing the glacier to change from advancing at a rate of 3.5 kma–1 to retreating at a rate of 1.9 km a–1. These results highlight the potential for atmospheric warming and surface meltwater to trigger glacier retreat, but also the difficulty of modelling calving rates, as crevasse water depth is difficult to determine either by measurement in situ or surface mass-balance modelling.

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