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Dissertations / Theses on the topic 'Ice mechanics'
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1
Pegler, Samuel Santeri. "The fluid mechanics of ice-shelf buttressing." Thesis, University of Cambridge, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.608122.
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Pervier, Marie-Laure. "Mechanics of ice detachment applied to turbomachinery." Thesis, Cranfield University, 2012. http://dspace.lib.cranfield.ac.uk/handle/1826/11572.
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Flying in icing conditions is a real hazard for aircraft as they can undergo potential disastrous increase in drag, reduction in maximum lift which lead to an
increase in fuel consumption. Additionally pitot tubes and other sensors can
become blocked or their operation compromised. Ice shed from other parts of
the aircraft can enter the engine and lead to blade damage. Whilst ice protection systems are comonly used on propellers, the potential benefit of applying
them to a fan have not, as yet, been considered suffi cient to o set the cost and
energy penalties of such system. As engines become larger, it is more diffi cult
to contain ice and self-shedding becomes an increasing hazard for the nacelle
and other parts downstream of the fan.
The main objectives of the project were to determine the mechanical proper-
ties of ice such as might form on an engine fan, in order to help Rolls-Royce in
building a finite elements model able to simulate ice shedding from fan blades.
Lots were written about ice however only little information about the mechanical properties of impact ice was available in the literature and the values which
were, were generally not applicable in the case of aeroengine in icing conditions. According to the literature and from Rolls-Royce photos and films of
ice shedding from fan blades, self-shedding mechanisms were ruled by adhesive
shear strength and tensile strength. Therefore, the experimental part of the
project consisted of measuring these two mechanical properties as well as the
density, the sti ness and the grain size of ice grown on titanium substrate.
Two test rigs were used to measure the mechanical properties: the \mode I"
and the \shear" test rig. The mode I test rig was already available and was
only modified in order to test more specimens during each run. This test al-
lowed to measure the pressure needed to remove the ice from the substrate in
a running icing tunnel. Using equations from the literature, fracture energy,
fracture toughness and tensile strength were calculated. The influence of ambient total temperature, cloud liquid water content and tunnel wind speed were
investigated. Tensile strength was found to be increasing as the total temperature is decreasing, decreasing as the LWC is increasing and going trough a
maximum as the tunnel wind speed is increasing. Values obtained lied in the range from 0.6 to 1.5 J.m-2 (corresponding to between 2 and 10 MPa) which
is, in general, higher than the ones reported by other authors. This difference
can be explained by the fact that the mode I test was conducted in a running
icing tunnel while the previous authors have conducted the mechanical test
after the tunnel has been stopped. In parallel, finite element models have been
developed and results similar to the experiments were obtained ...[cont.].
3
Fried, Mason. "Grounding Zone Process| Ice Mechanics and Margin Lakes, Kamb Ice Stream and Whillans Ice Stream, West Antarctica." Thesis, Portland State University, 2013. http://pqdtopen.proquest.com/#viewpdf?dispub=1542719.
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The lateral "corners" where Kamb and Whillans Ice Streams (KIS and WIS) discharge into the Ross Ice Shelf share common geometries and ice mechanical settings. At both corners of the now-stagnant KIS outlet, shear margins of apparently different ages confine regions with a relatively flat, smooth surface expression. These features are called the "Duckfoot" on the northern, right-lateral side and the "Goosefoot" on the other. It has been suggested, on evidence found in ice internal layers, that the flat ice terrains on KIS were afloat in the recent past, at a time when the ice stream grounding line was upstream of its present location. The overdeepening in the bed just upstream of the KIS grounding line supports this view of the past geometry.
The right-lateral margin at the outlet of the currently active WIS, the location of Subglacial Lake Englehardt (SLE), appears to have many similarities with the right lateral margin of KIS, though with a less developed looking inboard margin. This paper presents a mechanical analysis using surface and bed topography and velocity datasets comparing the Duckfoot flat ice terrain with the terrain around Subglacial Lake Englehardt. At both locations mechanical thinning along shear margins and lows in the bed topography redirects basal water routing towards the features. Here, I consider the history of these features and their role in ice stream variability by comparison of the relict and modern features and via numerical modeling of ice shelf grounding and ungrounding in response to variations in ice flow.
We propose two scenarios for the development of flat ice terrains/subglacial lakes at the outlets of ice streams. In the first, development of a lake in the hydraulic potential low along a shear margin forces a margin jump as shearing develops along the inboard shore of the margin lake. This thesis presents evidence for an inboard (relative to the main outboard shear margin) zone of shear along the inboard shoreline of SLE, suggesting that subglacial lakes along shear margins are capable of facilitating shear margin jumps. In the second, grounding line advance around a relative low in the bed, creating adjacent margins along the lakeshores, forms a remnant lake. Discerning which of these scenarios is appropriate at the KIS outlet has implications for understanding the history of the ice stream grounding line.
An ice flow model is used to place these local conditions in a regional context by studying the effect of internal perturbations, such as ice rise stagnation or inward margin jumps, on grounding line position. Bathymetry is important in determining ice stream flow in the ways that might not be otherwise realized in 1-D flow model studies. In the numerical modeling experiments, grounding line advance across the KIS outlet is mediated by the overdeepening in the bed and proceeds not in the direction of ice flow but transverse to flow. This finding adds complexity to both a flowline view of grounding line migration and the theory that grounding lines are unstable in the presence of inward sloping bed topography.
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Fried, Mason Joseph. "Grounding Zone Processes: Ice Mechanics and Margin Lakes, Kamb Ice Stream and Whillans Ice Stream, West Antarctica." PDXScholar, 2013. https://pdxscholar.library.pdx.edu/open_access_etds/1112.
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The lateral "corners" where Kamb and Whillans Ice Streams (KIS and WIS) discharge into the Ross Ice Shelf share common geometries and ice mechanical settings. At both corners of the now-stagnant KIS outlet, shear margins of apparently different ages confine regions with a relatively flat, smooth surface expression. These features are called the "Duckfoot" on the northern, right-lateral side and the "Goosefoot" on the other. It has been suggested, on evidence found in ice internal layers, that the flat ice terrains on KIS were afloat in the recent past, at a time when the ice stream grounding line was upstream of its present location. The overdeepening in the bed just upstream of the KIS grounding line supports this view of the past geometry.
The right-lateral margin at the outlet of the currently active WIS, the location of Subglacial Lake Englehardt (SLE), appears to have many similarities with the right lateral margin of KIS, though with a less developed looking inboard margin. This paper presents a mechanical analysis using surface and bed topography and velocity datasets comparing the Duckfoot flat ice terrain with the terrain around Subglacial Lake Englehardt. At both locations mechanical thinning along shear margins and lows in the bed topography redirects basal water routing towards the features. Here, I consider the history of these features and their role in ice stream variability by comparison of the relict and modern features and via numerical modeling of ice shelf grounding and ungrounding in response to variations in ice flow.
We propose two scenarios for the development of flat ice terrains/subglacial lakes at the outlets of ice streams. In the first, development of a lake in the hydraulic potential low along a shear margin forces a margin jump as shearing develops along the inboard shore of the margin lake. This thesis presents evidence for an inboard (relative to the main outboard shear margin) zone of shear along the inboard shoreline of SLE, suggesting that subglacial lakes along shear margins are capable of facilitating shear margin jumps. In the second, grounding line advance around a relative low in the bed, creating adjacent margins along the lakeshores, forms a remnant lake. Discerning which of these scenarios is appropriate at the KIS outlet has implications for understanding the history of the ice stream grounding line.
An ice flow model is used to place these local conditions in a regional context by studying the effect of internal perturbations, such as ice rise stagnation or inward margin jumps, on grounding line position. Bathymetry is important in determining ice stream flow in the ways that might not be otherwise realized in 1-D flow model studies. In the numerical modeling experiments, grounding line advance across the KIS outlet is mediated by the overdeepening in the bed and proceeds not in the direction of ice flow but transverse to flow. This finding adds complexity to both a flowline view of grounding line migration and the theory that grounding lines are unstable in the presence of inward sloping bed topography.
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McDaniel, Shannon M. "New techniques for the investigation of deformation mechanisms in flow of fine-grained ice Ih /." Thesis, Connect to this title online; UW restricted, 2005. http://hdl.handle.net/1773/6747.
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Le, Ngoc Chau. "Force and centre of pressure measurements during ice hockey skating with a regular and a modfied ice hockey skate." Thesis, McGill University, 2013. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=117022.
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Force and centre of pressure (COP) were measured during a forward skating task on ice using a standard hockey skate and a modified skate with an altered tendon guard and eyelet configuration which allows for increased dorsiflexion and plantarflexion. The objective of this study was to determine if those skate design changes would result in biomechanical changes in the skaters during forward skating. Both left and right skates were instrumented with a calibrated strain gauge force transducer system to measure forces and with an insole system used to measure the COP during the forward skating task. The modified skate showed a reduction of 14.5-24.3 mm in total anterior-posterior COP excursion (p < .05). This suggests that the modified skate changes the biomechanics of the skaters. However, a full body kinematic study might be needed in order to study the exact biomechanical changes.La force et le centre de poussée (CDP) ont été mesurés pendant le patinage sur glace en ligne droite en utilisant des patins de hockey standards et des patins de hockey modifiés avec un protecteur du tendon d'Achille plus flexible et une configuration différente des oeillets pour lacets permettant une plus grande dorsiflexion et flexion plantaire de la cheville. Le but de cette étude était de déterminer si ces changements de construction de patins ont une influence sur le mouvement biomécanique des patineurs pendant le patinage sur glace en ligne droite. Les patins gauches et droites ont été instrumentés avec un système d'estimation de la force calibré et avec un système de capteurs de pression en dessous de la semelle pour mesurer le CDP. L'utilisation du patin modifié s'est manifestée par une réduction de 14.5 à 24.3 mm du déplacement total du CDP dans la direction antéro-postérieure (p < .05). Celà suggère que l'utilisation du patin modifié a un effet sur la biomécanique des patineurs. Cependant, une étude cinématique du corps au complet serait peut-être nécéssaire afin d'étudier les changements biomécaniques exacts.
7
Stehn, Lars. "Tensile fracture of ice : test methods and fracture mechanics analysis." Doctoral thesis, Luleå tekniska universitet, Byggkonstruktion och -produktion, 1993. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-18394.
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This thesis is concerned with several aspects of fracture of both brackish (low salinity) sea ice and freshwater ice. The tests and analyses are confined to tensile, or in fracture mechanics language, Mode I, fracture. A large part of this thesis is dedicated to demonstrate that Linear Elastic Fracture Mechanics (LEFM) can be applicable on ice by laboratory and in-situ tests of defined specimens. All interpretations are made using the dicipline of LEFM.First, the development of a field test equipment called FIFT ( a Field Instrument for Fracture toughness Tests on ice) is described. The FIFT is used in both field and laboratory fracture toughness tests on brackish sea ice from the Gulf of Bothnia to describe porosity effects on the apparent fracture toughness, KQ, and estimate crack velocities. An appropriate speciment size, in terms of notch sensitivity, is then provided valid for grain sizes ranging from 1.6 to nearly 100 mm.An augmented use of the FIFT is then described where fracture toughness tests are performed on S1 type freshwater ice to investigate if similarities exist in the local KI fields for three different fracture geometries. The results indicate that, under comparable conditions, KQ is similar for all of the geometries. However, the type of specimen, has a marked influence on the character of the fracture surface.Then, the influence of structural anisotropy on the fracture toughness of S1 ice is investigated by fabricating and testing three different fracture geometries from a single ice core. This approach is suitable for both field and, as in this work, laboratory studies. There is a wide scatter in the KQ values. Possible explanations to the results are discussed in terms of the microstructural influences and specimen size effects.Finally, crack growth resistance measurements on large grained S1 ice is conducted. A new fracture geometry is used which is found to be extremely favorable of promoting stable, stick-slip, crack growth over a large portion of the uncracked ligament. Now a complete characterization of the fracture resistance curve is therefore possible, A negative fracture resistance KR-curve is evaluated for the S1 ice at -16°C.Godkänd; 1993; 20070426 (ysko)
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Tulaczyk, Slawek M. Kamb Barclay. "Basal mechanics and geologic record of ice streaming, West Antarctica /." Diss., Pasadena, Calif. : California Institute of Technology, 1999. http://resolver.caltech.edu/CaltechETD:etd-03092004-155058.
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Millgate, Thomas. "Ice-ocean interactions in north west Greenland." Thesis, University of Oxford, 2015. https://ora.ox.ac.uk/objects/uuid:f5c18faa-c027-4cbb-aa00-4849a323a9a1.
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Ice shelves play an important role in the mass balance of an ice sheet, by providing a link between the ocean and ice. Melting at the base of an ice shelf can play a vital role in its mass balance and stability. Topographic channel features have been found on the base of ice shelves, and have been found to alter melting, however the mechanism behind this alteration is unknown. Petermann Glacier is a major outlet glacier in North West Greenland, draining approximately 6% of Greenland Ice Sheet. It terminates in a long, thin ice shelf, constrained within a high-walled fjord. The ice shelf has pronounced longitudinal channel features on its base, which limited observations suggest direct ocean currents in a mixed layer of ocean and melt waters, focusing melt in these regions. Petermann Glacier underwent two large calving events in 2010 and 2012, and the impact of these events, or possible further calving events, on basal melting is unknown. Using the MITgcm to model the ocean cavity beneath an idealised ice shelf, this thesis discusses the impact of basal channels on interactions at the ice base and circulation within the cavity. This is supplemented with a modelling investigation into the interactions beneath Petermann Glacier, and the impact of recent calving events. The inclusion of channels was found to have a stabilising effect on the ice shelf by decreasing the mean basal melt rate, caused by the refocusing, and decrease in intensity of, the meltwater layer flow beneath the ice shelf. This stabilisation and resulting 'survivor bias' explains why channels are commonly found on the base of warm water ice shelves. The model of Petermann Glacier found similar melt patterns to observational studies, however with a lesser magnitude. The calving events of 2010 and 2012 removed areas of ice shelf with low melt rates, resulting in little impact on the overall volume of ice removed through ocean melting, though further calving would vastly reduce the volume of ice melted. One consequence of calving is the increase in melting-induced undercutting at the ice front, leading to the potential for enhanced secondary calving.
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Williams, Timothy D. C., and n/a. "Reflections on ice : scattering of flexural gravity waves by irregularities in Arctic and Antarctic ice sheets." University of Otago. Department of Mathematics & Statistics, 2006. http://adt.otago.ac.nz./public/adt-NZDU20060907.120444.
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This thesis studies the scattering properties of different types of imperfections in large Arctic and Antarctic ice sheets. Such irregularities include cracks, pressure ridges and both open and refrozen leads. The scattering by a transition region between sea ice and a very thick ice shelf, for example as is found in the Ross Sea in Antarctica, is also treated.
Methods of solution are based on applications of Green�s theorem to the appropriate situation, which leads to either a single integral equation or a pair of coupled integral equations to be solved at the boundary between the ice and the sea water. Those equations over a finite interval are solved using numerical quadrature, while those over semi-infinite ranges are solved using the Wiener-Hopf method. Results calculated using different techniques are able to be checked against each other, giving us great confidence in their accuracy. In particular, the scattering by three ice sheets of different thicknesses is confirmed analytically by mode-matching coupled with the residue calculus technique.
The scattering by the single irregularities is investigated partly for its own sake, and partly with the aim of using it to treat the scattering when large numbers of features are included in a single ice sheet. The principal objective of doing this is to observe the change in the general amounts of reflection and transmission as the background ice thickness is changed. There is enough variation in our results for us to conclude that there is definite potential for using the change in an incident wave spectrum after passing through a given ice field to estimate the background ice thickness.
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Kyrke-Smith, Teresa Marie. "Ice-stream dynamics : the coupled flow of ice sheets and subglacial meltwater." Thesis, University of Oxford, 2014. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.629515.
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Ice sheets are among the key controls on global climate and sea level. A detailed understanding of their dynamics is crucial to make accurate predictions of their future mass balance. Ice streams are the dominant negative component in this balance, accounting for up to 90% of the Antarctic ice flux into ice shelves and ultimately into the sea. Despite their importance, our understanding of ice-stream dynamics is far from complete. A range of observations associate ice streams with meltwater. Meltwater lubricates the ice at its bed, allowing it to slide with less internal deformation. It is believed that ice streams may appear due to a localisation feedback between ice flow, basal melting and water pressure in the underlying sediments. This thesis aims to address the instability of ice-stream formation by considering potential feedbacks between the basal boundary and ice flow. Chapter 2 considers ice-flow models, formulating a model that is capable of capturing the leading-order dynamics of both a slow-moving ice sheet and rapidly flowing ice streams. Chapter 3 investigates the consequences of applying different phenomenological sliding laws as the basal boundary condition in this ice-flow model. Chapter 4 presents a model of subglacial water flow below ice sheets, and particularly below ice streams. This provides a more physical representation of processes occurring at the bed. Chapter 5 then investigates the coupled behaviour of the water with the sediment, and Chapter 6 the coupled behaviour of the water with the ice flow. Under some conditions this coupled system gives rise to ice streams due to instability of the internal dynamics.
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Steinbach, Florian [Verfasser], and Ilka [Akademischer Betreuer] Weikusat. "Numerical modelling of deformation and recrystallisation mechanics in ice and ice-air aggregates / Florian Steinbach ; Betreuer: Ilka Weikusat." Tübingen : Universitätsbibliothek Tübingen, 2017. http://d-nb.info/1165577321/34.
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Garrigues, Laurent. "Statistical analysis and forecasting of sea ice conditions in Canadian waters." Thesis, McGill University, 2001. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=19621.
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Historical data of sea ice concentration in Canadian waters are analysed using projections methods (Principal Component Analysis, Singular Value Decomposition, Canonical Correlation Analysis and Projection on Latent Structures) to identify the main patterns of evolution in the sea ice cover. Three different areas of interest are studied: (1) the Gulf of St Lawrence, (2) the Beaufort Sea and (3) the Labrador Sea down to the east coast of Newfoundland. Forcing parameters that drive the evolution of the sea ice cover such as surface air temperature and wind field are also analysed in order to explain some of the variability observed in the sea ice field. Only qualitative correlations have been identified, essentially because of the singular nature of the sea ice concentration itself and the accuracy of available data. However, several statistical models based on identified patterns have been developed showing forecasting skills far better than those of the persistence assumption, which currently remains one of the best 'model' available. Forecasts are tested over periods of time ranging from a few days to several weeks. Some of these models constitute innovative approaches in the context of statistical sea ice forecasting. Some others models have been developed using a probabilistic approach. These models provide forecasts in terms of sea ice severity (low-medium-high), which is often accurate enough for navigation purposes for the three areas of interest. Forecasting skills of these models are also better than the persistence assumption. Finally, an existing dynamic sea-ice model has been adapted and used to predict sea ice conditions in the Gulf of St Lawrence during the Winter season 1992-1993. Simulations provided by this model are compared to the forecasts of different statistical models over the same period of time.
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Xiao, Jing. "Damage and fracture of brittle viscoelastic solids with application to ice load models." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape11/PQDD_0019/NQ47510.pdf.
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Eskandarian, Mojtaba. "Ice shedding from overhead electrical lines by mechanical breaking : a ductile model for viscoplastic behaviour of atmospheric ice = Délestage de glace des câbles électriques par bris mécaniques : un modèle du comportement ductile viscoplastique de la glace atmosphérique poreuse /." Thèse, Chicoutimi : Université du Québec à Chicoutimi, 2005. http://theses.uqac.ca.
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Jacobson, Herbert Paul. "Folding of stratigraphic layers in ice domes /." Thesis, Connect to this title online; UW restricted, 2001. http://hdl.handle.net/1773/6837.
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Choi, Kyungsik. "A damage mechanics approach to the three dimensional constitutive modelling of ice deformation." Thesis, Massachusetts Institute of Technology, 1989. http://hdl.handle.net/1721.1/51468.
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Zane, Lisa. "Force measures at the hand-stick interface during ice hockey slap and wrist shots." Thesis, McGill University, 2012. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=110526.
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The purpose of this study was to quantify the contact forces between the lower and upper hands to the stick shaft during the ice hockey slap and wrist shot. Four cohorts (male/female x high/low calibre; HC, LC) of ice hockey players were tested using three sticks of different shaft bending stiffnesses (77, 87, 102). Forty-one subjects (21 male, 20 female) performed seven slap and seven wrist shots with each of the three stick types. Force at the stick-hand interface was recorded at 1000 Hz using 32 piezoresistive sensors about the shaft at the upper and lower-hand grip locations. The results demonstrated the feasibility for direct measurement of forces at the hand-stick interface while executing shooting tasks in ice hockey. As anticipated, peak forces acquired during both the slap and wrist shot differed by calibre and by gender, with males exhibiting higher forces than females, and HC players demonstrating higher forces than LC players, within each gender; however, stick type was not a significant factor. Notably, each player displayed unique, repeatable "force signatures". In general, for both slap and wrist shots, grip force patterns demonstrated typical bimanual coordination patterns pertinent to understanding the mechanical dynamic control of the stick for effective performance.Le but de cette étude était d'examiner les forces de contact entre les mains et le baton de hockey pendant l'exécution de lancers frappés et de tirs du poignet. Quatre cohortes (homme/femme x haut / bas calibre; HC, LC) de joueurs de hockey sur glace ont été testés en utilisant trois bâtons de rigidités différentes (77, 87, 102). Quarante et un sujets (21 hommes, 20 femmes) ont effectué sept lancers frappés et sept tirs du poignet avec chacun des trois types de bâton. La force de pression a été enregistrée à 1000 Hz en utilisant 32 capteurs piézorésistifs aux interfaces entre la main et le bâton. Les résultats ont démontré la faisabilité de la mesure directe des forces à l'interface main-bâton lors de l'exécution de tirs au hockey sur glace. Les forces de pointe atteintes au cours de lancers frappés et de tirs du poignet différaient en fonction du calibre et du sexe, les hommes présentant des forces supérieures comparativement aux femmes. De plus, les joueurs de HC ont démontré des forces supérieures par rapport aux joueurs LC. Par contre, le type de bâton ne représentait pas un facteurs significatif pour la production de force qui plus est, chaque joueur a affiché une 'signature' de force reproductible et constante. En général, les modèles de forces pour les lancers frappés et les tirs des poignets ont démontré des pattrons de coordination bimanuelle à la compréhension du contrôle mécanique dynamique du bâton et possiblement a l'évaluation de la performance.
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Forget, Samuel. "Comparisons of player calibers and skate models during an ice hockey explosive transitional maneuver." Thesis, McGill University, 2014. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=123253.
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The ground (ice) reaction force and the plantar foot pressure variables were measured during an explosive transitional maneuver, stop and go, skating task on ice using: 1) regular hockey skate and 2) a modified skate with an altered tendon guard and eyelet configuration which allows for increased dorsiflexion and plantarflexion. The objective of this study was to describe the differences in skating mechanics and kinetics between high and low caliber skaters and between the two different skate models during the specific explosive transitional, stop and go, skating task. Both the left and right skates were instrumented with a calibrated strain gauge force transducer system to measure the ground (ice) reaction force and with an insole system used to measure the plantar foot pressure variables during the stop and go skating task. Similar CoP and vertical force results were observed between the two skate models; however, high caliber skaters showed a reduction of 10.7 (inside skate) and 15.2 (outside skate) mm in total antero-posterior CoP excursion during the stop phase (p<0.05). In conclusion, specific postural control patterns were observed between high and low caliber skaters. However, a full body kinematic study might be needed in order to study the exact biomechanical changes.Les variables de la force de réaction du sol (glace) et de la pression plantaire du pied ont été mesurées pendant une manœuvre de transition explosive, "stop and go", de patinage sur glace. 1) à l'aide de patins de hockey standard et 2) des patins de hockey modifiés avec un protecteur du tendon d'Achille plus flexible et une configuration différente des œillet pour lacets permettant une plus grande flexion dorsale et plantaire de la cheville. Le but de cette étude était d'illustrer les différences de la mécanique du patinage et la cinétique entre les patineurs de haut et bas calibre et entre les deux modèles de patins pendant la tâche de patinage spécifique du "stop and go". Tant les patins de gauches et de droites ont été instrumentés avec un système d'estimation de la force calibré et avec un système de capteurs de pression en dessous de la semelle pour mesurer les variables de la pression plantaire du pied pendant la tâche de patinage du "stop and go". Les deux modèles de patin ont démontré des résultats similaires quant aux variables du Centre de Pression (CdP) et de la force verticale. Toutefois, les patineurs de haut calibre ont démontré une réduction de 10,7 (patin intérieur) et 15.2 (patin extérieur) mm concernant le déplacement total du CdP antéro-postérieur pendant la phase d'arrêt (p <0,05). En conclusion, des modèles spécifiques du contrôle postural ont été observées entre les patineurs de haut et de bas niveau. Néanmoins, une étude cinématique exhaustive du corps humain serait manifestement nécessaire afin d'étudier les changements biomécaniques exacts.
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Ouckama, Ryan. "Time series measurement of force distribution in ice hockey helmets during varying impact conditions." Thesis, McGill University, 2013. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=119435.
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Modern sport helmets have been effective in reducing catastrophic head injuries such as skull fracture and subdural hematoma; yet, the high prevalence of minor traumatic brain injuries (mTBI) is an unresolved public health concern. Consequently, there is a need for greater scrutiny in a helmet's ability to mitigate collision forces that may correspond to mTBI risk. Current safety standards primarily assess a helmet's ability to minimize the whole head's peak acceleration during blunt impacts. Absent are dynamic measures local to the impact site itself due to the technical challenge to spatial map high impact force magnitudes with high temporal resolution. Inclusion of the latter measures may enhance the functional assessment of helmets. Thus, the aim of this research was to develop a localized impact mapping system (LIMS) for placement between the helmet and head interface and then to utilize the LIMS to evaluate the mechanical behaviour of various padding foams and helmets during controlled headform drop and projectile collision tests. Interposed between the helmet shell/padding and head surface, this LIMS consists of an array of discrete, thin force sensors connected to a compact signal conditioner and high speed data acquisition digital recorder. A first study demonstrated the feasibility of the LIMS to accurately capture impact events in terms of both force magnitude and temporal response. The results of this initial study demonstrated that the system could capture impact forces with acceptable error (~5%) and high correlation (0.97) between measures of global force and the sensor array. Furthermore, the LIMS demonstrated the ability to capture impact "footprints" that functionally differentiated material properties of density and temperature. A second study incorporated the LIMS as part of a standard controlled surrogate headform drop test for blunt impacts. The LIMS performed equally well on the curved cranial surface geometry of the headform and was able to differentiate unique impact contact distribution patterns based on the ice hockey helmet model's shell and padding configurations, including identification of high focal force concentrations (>16 MPa) during side impact. Of note, global head impact acceleration measures did not correspond to the magnitude of localized contact forces (R-square=0.22), but did correspond to net global contact force (R-square=0.98). A third study used the LIMS between a Hybrid III surrogate headform and an ice hockey helmet during controlled puck projectile collisions. The LIMS was effective at capturing local force distributions dynamics for short impact events lasting 2-4 ms, and again was able to distinguish between varied helmet model's padding materials and installed configurations. Five helmet models were subject to highly localized puck impact at two different velocities (V1=24.2 m/s, V2=33.3 m/s). At V2, peak contact pressures, averaged across all helmet models, were nearly double (393 N/cm^2) those recorded at the same location during vertical drop testing (201 N/cm^2). Again, linear acceleration data did not discern these differences in localized pressures. In summary, this novel testing approach provides an instrument for the assessment of helmet design and material properties on local impact dynamics, and demonstrates merit as an industrial and research tool to enhance head protection.Les casques de sport modernes ont été efficaces pour réduire les traumatismes crâniens sévères tels que les fractures du crâne et les hématomes sous-duraux. Malgré tout, la prévalence élevée des lésions cérébrales traumatiques mineures reste un problème de santé publique non résolu. Par conséquence, il existe un besoin important pour un examen plus approfondi de la capacité des casques à atténuer les forces de collision qui pourraient correspondre à un risque de traumatisme cérébral mineur. Les normes actuelles évaluent principalement l'efficacité des casques à minimiser les accélérations maximales de la tête lors d'impacts contondants. L'absence de mesures dynamiques locales, plus précisément au site d'impact, est surtout dû au défi technique qui est d'insérer des matrices sensorielles avec une haute résolution temporelle. Le développement de cette dernière technique de mesure pourrait améliorer l'évaluation fonctionnelle des casques en général. Ainsi, l'objectif principal de cette recherche était de développer un système de cartographie d'impact local (CIL) tout en permettant l'insertion de ce système entre le casque et la tête, et ainsi, utiliser le CIL afin d'évaluer les caractéristiques mécaniques de differentes mousses de rembourrage et différents casques au cours de chute et de collision contrôlée sur une fausse tête. Interposé entre la calotte/rembourrage et la surface de la tête, ce CIL est constitué d'un réseau de capteurs de force discrets, minces, connectés à une grande vitesse d'acquisition de données numériques. Une première étude a démontré la faisabilité d'utiliser le CIL pour capturer avec précision des événements d'impact en termes d'amplitude et de force ainsi que la réponse temporelle. Par ailleurs, le CIL a démontré la capacité de capturer les «empreintes» d'impact et de différencier fonctionnellement divers matériaux en mousse et des densités. Une deuxième étude a intégré le CIL dans le cadre d'une norme d'essai contrôlé de fausse tête de substitution lors de chute sur objets contondants. Le CIL s'est révélé tout aussi précis sur la géométrie de la surface crânienne courbe et a été en mesure de différencier les modèles uniques d'impact de contact de distribution basé sur le modèle de coque des casques de hockey et de configurations de remplissage, y compris l'identification de concentrations élevées de force de contact (>16 MPa). Fait à noter, l'impact global des mesures d'accélération de la tête ne correspond pas nécessairement à l'ampleur des forces d'intervention (R-square=0.22). Une troisième étude a utilisé le CIL entre une fausse tête de substitution Hybrid III et un casque de hockey sur glace lors de collisions de projectiles. Le CIL est efficace pour capturer des distributions locales de forces dynamiques lors d'événements de moins de 4 ms, et encore une fois a été en mesure de faire la distinction entre les matériaux de rembourrage des modèles de casques variés. En résumé, cette approche de test innovatrice s'est avérée être un instrument précis pour l'évaluation de la conception du casque et des propriétés des matériaux sur la dynamique d'impact local, et démontre le mérite d'un outil industriel et de recherche visant à améliorer la protection de la tête.
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Melanson, Paul M. "Damage and microstructural change in laboratory grown ice under high pressure zone conditions /." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape17/PQDD_0002/MQ34208.pdf.
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Matbou, Riahi Mehran. "Numerical and experimental studies of the mechanical behaviour at the ice/aluminium interface = Études numérique et expérimentale du comportement mécanique à l'interface glace/aluminium /." Thèse, Chicoutimi : Université du Québec à Chicoutimi, 2007. http://theses.uqac.ca.
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Thèse (M.Eng.) -- Université du Québec à Chicoutimi, 2007.La p. de t. porte en outre: Mémoire présenté à l'Université du Québec à Chicoutimi comme exigence partielle de la maîtrise en ingénierie. CaQCU Bibliogr.: f. 137-143. Document électronique également accessible en format PDF. CaQCU
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Faria, Santos Sérgio Henrique. "Mechanics and thermodynamics of mixtures with continuous diversity from complex media to ice sheets /." [S.l. : s.n.], 2003. http://elib.tu-darmstadt.de/diss/000307.
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Choi, Dong Ho. "Viscoplasticity and damage mechanics models for rate-dependent materials and their application to ice." Thesis, Massachusetts Institute of Technology, 1997. http://hdl.handle.net/1721.1/42583.
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McTaggart, Kevin Andrew. "Hydrodynamics and risk analysis of iceberg impacts with offshore structures." Thesis, University of British Columbia, 1989. http://hdl.handle.net/2429/30733.
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The evaluation of design iceberg impact loads for offshore structures and the influence
of hydrodynamic effects on impact loads are examined. Important hydrodynamic effects include iceberg added mass, wave-induced oscillatory iceberg motions, and the influence of a large structure on the surrounding flow field and subsequent velocities of approaching icebergs. The significance of these phenomena has been investigated using a two-body numerical diffraction model and through a series of experiments modelling the drift of various sized icebergs driven by waves and currents approaching a large offshore structure. Relevant findings from the hydrodynamic studies have been incorporated into two probabilistic models which can be used to determine design iceberg collision events with a structure based on either iceberg kinetic energy upon impact or global sliding force acting on the structure. Load exceedence probabilities from the kinetic energy and sliding force models are evaluated using the second-order reliability method. Output from the probabilistic models can be used to determine design collision parameters and to assess whether more sophisticated modelling of various impact processes is required. The influence of the structure on velocities of approaching icebergs is shown to be significant
when the structure horizontal dimension is greater than twice the iceberg dimension. As expected, wave-induced oscillatory motions dominate the collision velocity for smaller icebergs but have a negligible effect on velocity for larger icebergs.Applied Science, Faculty of
Civil Engineering, Department of
Graduate
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Kermani, Koosheh Majid. "Ice shedding from cables and conductors : a cracking model of atmospheric ice = Délestage de glace des câbles et des conducteurs : un modèle de rupture fragile de la glace atmosphérique /." Thèse, Chicoutimi : Université du Québec à Chicoutimi, 2007. http://theses.uqac.ca.
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Thèse (D.Eng.) -- Université du Québec à Chicoutimi, 2007.La p. de t. porte en outre: Thèse présentée à l'Université du Québec à Chicoutimi comme exigence partielle au doctorat en ingénierie. CaQQUQ Bibliogr.: f. [211]-220. Document électronique également accessible en format PDF. CaQQUQ
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Baig, Zubair. "Functional mechanical assessment of foot and ankle stiffness and work production in ice hockey skate boots." Thesis, McGill University, 2011. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=97258.
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Ice hockey is a sport characterized by high speeds, sharp turns and abrupt stops. As a result of these explosive and agile movements, the interaction of the foot and ankle with the skate boot is fundamental for optimal stability and propulsion. The purpose of this study was to determine the nature of this mechanical coupling in both a conventional and prototype skate models. In phase one, a Biodex System 4 Pro dynamometer was used to isolate the foot and ankle / boot dynamics in sagittal and frontal plane movements. Three footwear conditions were evaluated (control shoe, a skate boot in production and a modified skate boot prototype). In phase two, lower body kinematics were assessed using 3D motion capture to determine if the above skate models would yield different joint movement coordination during skating push-offs using the two skate boot models. When comparing the three foot conditions, there was a significantly greater range of motion observed in the shoe control and modified skate boot than the regular skate boot (65.2 deg vs. 52.4 deg vs. 35.7 deg, p < 0.05). The total work done was only significant in the shoe control over the regular skate boot (16 kJ vs. 8.9 kJ, p < 0.05). In phase two, only the maximum plantar flexion was greater with the modified skate (11.3 deg vs. 1.3 deg, p < 0.05). The biodex dynamometer was able to discern differences between the three types of footwear using the dependent variables selected. Using a combination of the active and passive modes, this system has provided a valuable measurement of quantifying boot stiffness characteristics.Une vitesse de jeu rapide, les virages brusques ainsi que les arrêts soudains sont des caractéristiques bien particulières au hockey sur glace. Considérant ces mouvements explosifs et agiles, l'interaction entre le pied, la cheville ainsi que la botte du patin devient fondamentale pour obtenir une propulsion et une stabilité optimale. Le but de cette études était de déterminer la nature cette interaction mécanique pour un modèle de patin a glace conventionnel ainsi que pour un prototype. Dans un premier temps, un dynamomètre Biodex System 4 a été utilisé pour isoler de façon dynamique le pied et la cheville/patin dans les plans sagittal et frontal. Trois conditions expérimentales ont été évaluées (soulier contrôle, patin commercialisé ainsi qu'un patin modifié). Par la suite, la cinématique des membres inférieurs fut mesurée en utilisant une système de capture du mouvement pour déterminer si les différentes botte de patin affecteraient la coordination motrice lors d'un départ.En comparant les trois conditions de botte, une différence significative a été observée pour l'amplitude de mouvement entre le soulier et le patin modifié et le patin commercial (65.2° vs. 52.4° vs. 35.7°, p < 0.05). Le travail total était seulement significatif entre le soulier et le patin commercial (16 kJ vs 8.9 kJ, p < 0.05). Pour la deuxième phase, seulement la flexion plantaire maximale était plus grande avec le patin modifié 11.3° vs. 1.3°, p < 0.05).Le dynamomètre Biodex a pu clairement discerner des différences entre les différentes conditions de botte pour les variables dépendantes sélectionnées. En utilisant les modes passifs et actifs, le système a permis de générer une méthode de quantification caractéristique de la rigidité de bottes.
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Magee, Patrick. "Whole-body predictors of wrist shot accuracy in ice hockey: a kinematic analysis by way of motion capture." Thesis, McGill University, 2009. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=67030.
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Abstract The purpose of this study was to identify joint angular kinematics that correspond to shooting accuracy in the stationary ice hockey wrist shot. Twenty-four subjects participated in this study, each performing 10 successful shots to four shooting targets. An eight-camera infra-red motion capture system (240 Hz), using passive reflective markers, was used to record motion of the joints, hockey stick, and puck throughout the performance of the wrist shot. A multiple regression analysis was carried out to examine whole-body kinematic variables with accuracy scores as the dependent variable. Results indicate that no one body region predominated as a predictor of accuracy across all four shooting targets since the wrist shot's general movement pattern required that one or more of the body's joints modulate its movement amplitude, rate and timing to achieve an accurate outcome. Significant accuracy predictors were identified in the lower limbs, torso and upper limbs. An accurate outcome was associated with the following characteristics: The lower body seemed to provide a stable base for support, but also contributed to initiation of movement in the form of weight transfer towards the intended target. We propose that the trail leg seemed to offset rotational motion that could potentially upset the stability of the system if not properly managed. Additionally, angular kinematics at the pelvis, spine and thorax appeared to orient the trunk such that the upper limbs can optimally function to achieve an accurate outcome, and also undoubtedly contributed to force production. And finally, accuracy was associated with more dynamic use of the lead arm specifically at the wrist and shoulder.AbrégéL'objectif premier de cette étude était d'identifier les mouvements caractéristiques du corps des joueurs de hockey correspondant à la précision de tirs du poignet stationnaire à travers différents niveaux d'habiletés. Un total de vingt-quatre sujets ont fait partie de l'échantillon. Chacun d'eux ont dû réussir correctement dix lancers dans chacune des quatre différentes cibles. La performance des sujets a été évaluée en mesurant la cinématique du corps, du bâton et de la rondelle à l'aide de marqueur réfléchissants qui ont été filmé à l'aide d'un système d'analyse du mouvement composé de huit caméra infrarouge (Vicon®), le tout étant enregistré à 240 Hz. Avec le niveau de précision comme variable dépendante, une analyse de régression multiple a été effectuée avec les variables cinématiques de toutes les articulations. Les résultats ont démontrés qu'il n'y a pas de prédicteurs universels à travers les différentes cibles considérant qu'une ou plusieurs articulations peuvent ajuster leurs vitesses, amplitudes et séquences pour effectuer un lancer précis. Des prédicteurs important ont été identifiés dans les membres inférieurs, le tronc ainsi que dans les membres supérieur. Les membres inférieurs semblent permettent une base de support stable ainsi qu'un transfert de poids efficace en direction de la cible visée. De plus, la jambe arrière permettrait de contrer le momentum angulaire qui pourrait débalancé le système en équilibre. Le déplacement angulaire du tronc (pelvis, thorax et colonne lombaire) permet d'orienter de façon à ce que les membres supérieurs puissent bouger de façon optimale en plus de contribuer à la production de force transmisse à la rondelle. Pour terminer, la précision semble être associée à un contrôle plus dynamique du poignet et de l'épaule du membre supérieur contrôlant le haut du bâton.
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Price, Stephen F. "Development and applications of a full-stress flowband model for ice using the finite volume method /." Thesis, Connect to this title online; UW restricted, 2006. http://hdl.handle.net/1773/6797.
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Knight, Christopher J. "Hydrogen bond topology order/disorder transitions in ice and the behavior of defects in a disordered ice lattice /." Columbus, Ohio : Ohio State University, 2009. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1236788109.
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Javan-Mashmool, Mandana. "Theoretical and experimental investigations for measuring interfacial bonding strength between ice and substrate." Thèse, Chicoutimi : Université du Québec à Chicoutimi, 2005. http://theses.uqac.ca.
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Levis, Demian. "Two-dimensional Spin Ice and the Sixteen-Vertex Model." Phd thesis, Université Pierre et Marie Curie - Paris VI, 2012. http://tel.archives-ouvertes.fr/tel-00763350.
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Cette thèse présente une étude complète des propriétés statiques et dynamiques du modèle à seize vertex en 2D, une version simplifiée de la glace de spin avec interactions dipolaires. Après une discussion générale sur le magnétisme frustré, et la glace de spin en particulier, on justifie l'introduction de notre modèle pour étudier le comportement collectif de la glace de spin. On utilise un algorithme de Monte Carlo à temps continu avec une dynamique locale qui nous permet d'analyser les phases d'équilibre et les propriétés critiques du modèle 2D. On compare nos résutats avec les resultats obtenus dans les cas où le système est intégrable. On définit ensuite le modèle sur des arbres orientés et on applique une approximation du type Bethe-Peierls. Afin de discuter le domaine de validité de cette approche, on compare les résultats ainsi obtenus avec les résultats exacts et numériques obtenus pour le modèle 2D. L'apparition récente des glaces de spin artificielles suggère un certain choix des paramètres du modèle. On montre que le modèle à seize vertex décrit de façon précise la thermodynamique de la glace de spin artificielle. On présente en détail le diagramme de phase et la nature des phases d'équilibre du modèle à seize vertex. Afin d' inclure l'effet des fluctuations thermiques responsables de apparaition de défauts ponc- tuels dans la glace de spin, on construit une extension stochastique du modèle intégrable à six vertex. On étudie, par l'intermédiaire de simulations Monte Carlo, comment le système s'ordonne dans le temps après différentes trempes. On analyse l'évolution de la densité de défauts et on iden- tifie les mécanismes dynamiques qui pilotent la relaxation vers ses différentes phases d'équilibre. On montre ainsi que la dynamique donne lieu à du "coarsening" et qu'elle vérifie l'hypothèse de "scaling" dynamique. On discute le rôle des défauts topologiques étendus et ponctuels présents dans le système au cours de l'évolution. Finalement, on étudie la présence d'un régime dynamique où le système reste gelé pendant de longues périodes de temps, ce qui à été observé dans la glace de spin dipolaire en 3D.
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Levis, Demian. "Two-dimensional spin ice and the sixteen-vertex model." Phd thesis, Paris 6, 2012. http://www.theses.fr/2012PA066414.
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Cette thèse présente une étude détaillée des propriétés statiques et dynamiques du modèle à seize vertex en 2D, une version simplifiée de la glace de spin avec interactions dipolaires. Après une discussion générale sur le magnétisme frustré, et la glace de spin en particulier, on justifie l'introduction de notre modèle afin d'étudier le comportement collectif de la glace de spin. On utilise un algorithme de Monte Carlo à temps continu avec une dynamique locale afin d' analyser les phases d'équilibre et les propriétés critiques du modèle 2D. On compare nos résultats avec les résultats obtenus dans les cas o`u le système est intégrable. On définit ensuite le modèle dans sur des arbres orientés définis de façon adéquate, puis on applique une approximation du type Bethe-Peierls pour l'étude des phases d' équilibre du modèle. On discute le domaine de validité de cette approche et on compare les résultats ainsi obtenus avec les résultats exacts et numériques obtenus pour le modèle 2D. L'apparition récente des glaces de spin artificielles suggèrent un certain choix des paramètres du modèle. On montre que le modèle à seize vertex décrit de façon précise la thermodynamique de la glace de spin artificielle. Nos résultats théoriques sont quasi-qualitativement en accord avec les données expérimentales en dehors du point critique. On présente en détail le diagramme de phases et la nature des phases d'équilibre du modèle à seize vertex. Notre modèle est construit comme une extension stochastique du modèle intégrable à six vertex pour ainsi inclure l'effet des fluctuations thermiques qui font naturellement apparaitre des défauts. On étudie, par l'intermédiaire de simulations Monte Carlo, comment le système s'ordonne dans le temps après différentes trempes. On analyse l'évolution de la densité de défauts et on identifie les mécanismes dynamiques qui pilotent les différents types d'ordres vers lesquels le système évolue. On montre que la dynamique donne lieu à du ``coarsening" et elle vérifie l'hypothèse de ``scaling" dynamique. On discute le rôle dans la dynamique des défauts topologiques étendus et ponctuels présents dans le système. Finalement, on étudie la présence d'un régime dynamique où le système reste gelé pendant de longues périodes de temps, ce qui a été observe dans la glace de spin dipolaire en 3DIn this thesis we present a thorough study of the static and dynamic properties of the 2D sixteen-vertex model or, in other words, a simplified version of the dipolar spin-ice model. After a general discussion on frustrated magnets, and spin-ice in particular, we motivate the introduction of our sixteen-vertex model in order to study the collective behaviour of spin-ice. We use a rejection-free continuous-time Monte Carlo algorithm with local spin-flip updates to analyse the equilibrium phases and the critical properties of the 2D model. We compare our results with the integrable cases. We extend the model to be defined on carefully chosen trees and employ a Bethe-Peierls approximation to study the equilibrium properties of generic vertex models. The range of validity of the approximation is discussed by comparing the results obtained analytically for the model defined on trees with the exact and numerical results obtained for the 2D model. Motivated by advent of artificial spin-ice realisations, we set the parameters of the model in order to reproduce the experimental situation. We show that the sixteen-vertex model gives an accurate description of the thermodynamics of artificial spin-ice samples. Our theoretical results are in quasi-quantitative agreement with experimental data obtained in as-grown samples away from the critical point. The phase diagram of the sixteen-vertex model and the nature of the equilibrium phases is presented in detail. Our vertex model is build as a stochastic extension of the integrable six-vertex model in order to include thermal fluctuations in the form of defects. We study the ordering dynamics of the system following different kind of quenches by means of Monte Carlo simulations. We analyse the evolution of the density of defects and we identify the dynamical mechanisms leading the different ordering processes. We show that the dynamics proceed through coarsening accordingly to the dynamical scaling picture. The interplay between localised and extended topological defects is discussed. We study in detail the existence of a dynamical arrest following a quench as observed in 3D dipolar spin-ice
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Kálmán, Tamás. "Dynamic behavior of iced cables subjected to mechanical shocks = Comportement dynamique des câbles recouverts de glace et soumis à des chocs mécaniques /." Thèse, Chicoutimi : Université du Québec à Chicoutimi, 2007. http://theses.uqac.ca.
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Thèse (D.Eng.) -- Université du Québec à Chicoutimi, 2007.La p. de t. porte en outre: Thèse présentée à l'Université du Québec à Chicoutimi comme exigence partielle du doctorat en ingénierie. Bibliogr.: f. 150-155. Document électronique également accessible en format PDF. CaQQUQ
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Bravo, Jimenez Ismael. "Detection and removal of wind turbine ice : Method review and a CFD simulation test." Thesis, Högskolan i Gävle, Energisystem, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:hig:diva-27798.
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Nowadays, the energy sector is facing a huge demand that needs to be covered. Wind energy is one of the most promising energy resources as it is free from pollution, clean and probably will arise as one of the main energy sources to prevent global warming from happening. Almost 10% of the global energy demand is coming from renewable resources. By 2050 this percentage is expected to grow to 60%. Therefore, efforts on wind turbine technology (i.e. reliability, design…) need to be coped with this growth. Currently, large wind energy projects are usually carried out in higher altitudes and cold climates. This is because almost all of the cold climates worldwide offer profitable wind power resources and great wind energy potential. Operating with wind turbines in cold climates bring interesting advantages as a result of higher air density and consequently stronger winds (wind power is around 10% higher in the Nordic regions). Not only benefits can be obtained but extreme conditions force to follow harsh conditions. Low temperatures and ice accretion present an important issue to solve as can cause several problems in fatigue loads, the balance of the rotor and aerodynamics, safety risks, turbine performance, among others. As wind energy is growing steadily on icy climates is crucial that wind turbines can be managed efficiently and harmlessly during the time they operate. The collected data for the ice detection, de-icing and anti-icing systems parts was obtained through the company Arvato Bertelsmann and is also based on scientific papers. In addition, computer simulations were performed, involving the creation of a wind tunnel under certain conditions in order to be able to carry out the simulations (1st at 0ºC, 2nd at -10ºC) with the turbine blades rotating in cold regions as a standard operation. In this project, Computational Fluids Dynamics (CFD) simulation on a 5MW wind turbine prototype with ice accretion on the blades to study how CL and CD can change, also different measures of ice detection, deicing and anti-icing systems for avoiding ice accumulation will be discussed. Simulation results showed a logical correlation as expected, increasing the drag force about 5.7% and lowering the lift force 17,5% thus worsening the turbine's efficiency.
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Bourbonnais, Martin. "Étude de la perte de portance due à la contamination des fluides antigivres par la dilution de la bruine verglacante /." Thèse, Chicoutimi : Université du Québec à Chicoutimi, 1997. http://theses.uqac.ca.
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Wang, Xiaofei. "Évaluation aérodynamique des fluides dégivrants et antigivre dilués et contaminés par la glace et la neige /." Thèse, Chicoutimi : Université du Québec à Chicoutimi, 1999. http://theses.uqac.ca.
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Yao, Lan. "Experimental and numerical study of dynamic crack propagation in ice under impact loading." Thesis, Lyon, 2016. http://www.theses.fr/2016LYSEI043/document.
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Les phénomènes liés au comportement à la rupture de la glace sous impact sont fréquents dans le génie civil, pour les structures offshore, et les processus de dégivrage. Pour réduire les dommages causés par l'impact de la glace et optimiser la conception des structures ou des machines, l'étude sur le comportement à la rupture dynamique de la glace sous impact est nécessaire. Ces travaux de thèse portent donc sur la propagation dynamique des fissures dans la glace sous impact. Une série d'expériences d'impact est réalisée avec un dispositif de barres de Hopkinson. La température est contrôlée par une chambre de refroidissement. Le processus dynamique de la rupture de la glace est enregistré avec une caméra à grande vitesse et ensuite analysé par des méthodes d'analyse d'images. La méthode des éléments finis étendus complète cette analyse pour évaluer la ténacité dynamique. Au premier abord, le comportement dynamique de la glace sous impact est étudié avec des échantillons cylindriques afin d'établir la relation contrainte-déformation dynamique qui sera utilisée dans les simulations numériques plus tard. Nous avons observé de multi-fissuration dans les expériences sur les échantillons cylindriques mais son étude est trop difficile à mener. Pour mieux comprendre la propagation des fissures dans la glace, des échantillons rectangulaires avec une pré-fissure sont employés. En ajustant la vitesse d'impact on aboutit à la rupture des spécimens avec une fissure principale à partir de la pré-fissure. L'histoire de la propagation de fissure et de sa vitesse sont évaluées par analyse d'images basée sur les niveaux de gris et par corrélation d'images. La vitesse de propagation de la fissure principale est identifiée dans la plage de 450 à 610 m/s ce qui confirme les résultats précédents. Elle varie légèrement au cours de la propagation, dans un premier temps elle augmente et se maintient constante ensuite et diminue à la fin. Les paramètres obtenus expérimentalement, tels que la vitesse d'impact et la vitesse de propagation de fissure, sont utilisés pour la simulation avec la méthode des éléments finis étendus. La ténacité d'initiation dynamique et la ténacité dynamique en propagation de fissure sont déterminées lorsque la simulation correspond aux expériences. Les résultats indiquent que la ténacité dynamique en propagation de fissure est linéaire vis à vis de la vitesse de propagation et semble indépendante de la température dans l'intervalle -15 à -1 degrésThe phenomena relating to the fracture behaviour of ice under impact loading are common in civil engineering, for offshore structures, and de-ice processes. To reduce the damage caused by ice impact and to optimize the design of structures or machines, the investigation on the dynamic fracture behaviour of ice under impact loading is needed. This work focuses on the dynamic crack propagation in ice under impact loading. A series of impact experiments is conducted with the Split Hopkinson Pressure Bar. The temperature is controlled by a cooling chamber. The dynamic process of the ice fracture is recorded with a high speed camera and then analysed by image methods. The extended finite element method is complementary to evaluate dynamic fracture toughness at the onset and during the propagation. The dynamic behaviour of ice under impact loading is firstly investigated with cylindrical specimen in order to obtain the dynamic stress-strain relation which will be used in later simulation. We observed multiple cracks in the experiments on the cylindrical specimens but their study is too complicated. To better understand the crack propagation in ice, a rectangular specimen with a pre-crack is employed. By controlling the impact velocity, the specimen fractures with a main crack starting from the pre-crack. The crack propagation history and velocity are evaluated by image analysis based on grey-scale and digital image correlation. The main crack propagation velocity is identified in the range of 450 to 610 m/s which confirms the previous results. It slightly varies during the propagation, first increases and keeps constant and then decreases. The experimentally obtained parameters, such as impact velocity and crack propagation velocity, are used for simulations with the extended finite element method. The dynamic crack initiation toughness and dynamic crack growth toughness are determined when the simulation fits the experiments. The results indicate that the dynamic crack growth toughness is linearly associated with crack propagation velocity and seems temperature independent in the range -15 to -1 degrees
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Bennani, Lokman. "Modélisation bidimensionnelle de systèmes électrothermiques de protection contre le givre." Thesis, Toulouse, ISAE, 2014. http://www.theses.fr/2014ESAE0037/document.
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Icing has since long been identified as a serious issue in the aeronautical world. Ice build up, due to the presence of supercooled water droplets in clouds, leads to degradation of aerodynamic and/or air intake performances, among other undesirable consequences. Hence aircraft manufacturers must comply with certifications and regulations regarding flight safety in icing conditions. In order to do so, ice protection systems are used. Due to the multi-physical context within which these systems operate, numerical simulation can be a valuable asset. The present work deals with the numerical modelling of electro-thermal ice protection systems. It is built around the development of three modules. Two of them are dedicated to modelling heat transfer in the system and in the ice block. The other one models the mechanical behaviour of ice and fracture. Hence, the mechanical properties of atmospheric ice are reviewed in order to identify some mechanical parameters relevant to the fracture model. The fracture mechanics numerical method is used to investigate possible ice shedding mechanisms, that is to say the mechanisms leading to the detachement of ice, which are not yet well understood. The final goal of this work is to propose a completely coupled 2nd generation simulation methodology for electro-thermal ice protection systems. Hence the feasibility of a coupled thermal computation with ice shedding prediction based on the developed modules is shownLe givrage a depuis longtemps été identifié comme une problématique sérieuse dans le monde aéronautique.L’accrétion de givre, due à la présence de gouttelettes d’eau surfondue dans les nuages, dégrade les performances aérodynamiques et le rendement des entrées d’air parmi d’autres conséquences néfastes. Ainsi, les avionneurs sont sujets à des règles de certifications concernant la capacité à voler en conditions givrantes. Pour se faire, des systèmes de protection contre le givre sont utilisés. En raison de la complexité des phénomènes physiques mis en jeux, la simulation numérique constitue un atout lors de la phase de conception. Ce travail de thèse porte sur la modélisation et la simulation numérique des systèmes électrothermiques de protection contre le givre. Il s’articule autour de trois approches de modélisation, qui ont donné lieu au développement de trois modules. Deux d’entre eux sont dédiés à la simulation du transfert de chaleur dans le système et dans la glace (changement de phase). Le troisième est lié à la modélisation du comportement mécanique du givre atmosphérique avec fissuration. Ainsi, les propriétés mécaniques du givre atmosphérique sont revues de façon à pouvoir identifier les paramètres intervenant dans le modèle de fissuration. Ce modèle est ensuite utilisé pour étudier les mécanismes possibles de détachement du givre, qui ne sont à l’heure actuelle pas encore bien compris. Le but final de ce travail est de proposer une méthodologie de simulation couplée pour les systèmes électrothermiques de protection contre le givre. Ainsi, la faisabilité d’un calcul couplé thermique-fissuration avec prédiction de détachement de givre est présentée
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Perron, Éric. "Modélisation du développement de la couche limité sur un film fluide /." Thèse, Chicoutimi : Université du Québec à Chicoutimi, 1993. http://theses.uqac.ca.
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El, Akkad Adil. "Étude comparative des perturbations de la couche limite et de la portance, sur la plaque plane et sur modèle d'aile, en présence de fluides dégivrants /." Thèse, Chicoutimi : Université du Québec à Chicoutimi, 1993. http://theses.uqac.ca.
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Dagli, Deniz. "Laboratory Investigations of Frost Action Mechanisms in Soils." Licentiate thesis, Luleå tekniska universitet, Geoteknologi, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-64184.
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Phase change of the water in the soil skeleton under cold climate conditions (also known as frost action in soils) affects soil properties and can be responsible for serious alterations in a soil body; causing damages (due to the volumetric expansion known as frost heave) to structures on or below the ground surface such as foundations, roads, railways, retaining walls and pipelines, etc. In order to improve the current design methods for roads against frost action, the Swedish Transport Administration (Trafikverket) has initiated a research program. The main goals of the program are to revise the existing frost heave estimation methods and improve the frost susceptibility classification system for subgrade soils. Literature was reviewed to gather the details of different freezing test equipment around the world and to identify common trends and practices for laboratory freezing tests. Based on the literature review and the collaboration with the University of Oulu, Finland an experimental apparatus was assembled for studying frost action in the laboratory. A detailed description of the experimental apparatus is given. Top to down freezing of specimens (of 10cm height and diameter) can be monitored while keeping track of water intake, vertical displacements (heave) and the temperature profile within the sample. Loads can be applied at the top of the sample to study the effects of overburden. Moreover, the test setup was modified with a camera system to have the option of recording the experiments. Disturbed samples of two different soil types were tested. Experiments with fixed and varying temperature boundary conditions were conducted to assess the validity of the assumptions for the frost heave estimation methods currently in use in Sweden. To this end, a qualitative relationship between frost heave and heat extraction rates based on theoretical equations was established. It was shown that there is a significant difference between the preliminary findings of the experimental work and the current system being used in Sweden to quantify heave. Image analysis techniques were used on two experiments that were recorded by the camera system. Image recording and correlation analyses provided detailed information about frost front penetration and ice lens formation(s) under varying temperature boundary conditions. Thawing has also been regarded in further studies. Results of the image analyses were compared to readings from conventional displacement measurements during the same test. Significant agreement between the results of image analyses and displacement measurements has been found. Image analysis was shown to be a viable method in further understanding of frost heave mechanisms. Shortcomings and disadvantages of utilizing the theoretical equations as well as the image analysis techniques were discussed. Potential remedies for overcoming the drawbacks associated with each approach are suggested. The work is concluded by discussing the potential improvements, planned upgrades (addition of pore pressure transducers) and the future experiments to be conducted.
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Wang, Yaohua 1959. "Heat transfer from open channel flow to an ice block and an array of ice blocks." Thesis, McGill University, 1991. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=60689.
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Two series of experiments were conducted to investigate the heat transfer processes from open channel flow to an ice block and an array of ice blocks. The first series of twelve tests were conducted to determine the heat transfer rate from the open channel crossflow to a single isolated ice block. During the experiment the ice block was gradually lowered into the crossflow while maintaining a constant volume of submergence. The ice block which initially had the shape of a circular cylinder, changed gradually to the shape of a cone yielding to the thermal erosion by the crossflow. The heat-transfer rate from the crossflow to the ice cone was greater than the rate to a hemisphere and also the rate to a circular cylinder. This higher heat transfer rate associated with the cone is explained by a 'heat-transfer concentration' phenomenon associated with the tip of the ice cone.In the second series of experiments, a packed array of ice blocks in the tightest arrangement was used to simulate a brash ice cover in the open channel flow. Six tests were conducted. The heat transfer rate from the open-channel flow to the brash ice cover was significantly higher than the rate to a smooth surface. The increase in heat transfer rate due to the 'roughness effect' was as high as 300 percent. However, due to the 'sheltering effect', the heat transfer rate from the flow to each of the ice cone in the array was only 35 percent of the rate to a single isolated ice cone with the same volume of submergence.
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Jaiswal, Vinay Kumar. "Finite element modeling of electric field distributions around a resistive glazed post station insulator covered with ice = Modélisation par éléments finis de la distribution du champ électrique autour d'un isolateur de poste avec une couche semi-conductrice recouvert de glace /." Thèse, Chicoutimi : Université du Québec à Chicoutimi, 2005. http://theses.uqac.ca.
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Safa, Niloufar. "Designing of frazil ice test rig." Thesis, Högskolan i Skövde, Institutionen för ingenjörsvetenskap, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:his:diva-14583.
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A large part of electricity in Sweden is produced by hydropower plants, which are a safe and pollution-free source for electricity production. In the cold season, when the temperature of water decreases to below zero, water can be frozen and different types of ice will be generated. Frazil Ice is one type of ice that is made by turbulent water. This type of ice flows into rivers and blocks trash racks. Trash racks prevent the entrance of different things such as leaves, woods, stones and fishes into the turbines, but when they are blocked by the ice, water cannot go through them, thus turbines cannot work. Träbena is a hydropower station located at the Ätran River in south Sweden, and it suffers from frazil ice problems during the winter. To solve this problem, a heating system has been installed on the trash rack to melt frazil ice. Currently, the heating system works manually, but for energy saving, an automatic switch has been designed with a capacity sensor to detect the frazil ice thus turning the heating system either on or off. A test rig should be designed to test the sensor’s performance as well as to discover the best program for that sensor. In this research, following certain constraints such as cold store and trash rack dimensions, a test rig has been designed to test the frazil ice detector, using different variables such as temperature and water flow. The model of the test rig has been evaluated by static analysis, and water flow has been simulated to show how the water becomes turbulent in the test rig.
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Kaya, Roni. "Energy Usage in Ice Rink Resurfacing." Thesis, KTH, Energiteknik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-212928.
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Ishallar kräver stora mängder energi för sin verksamhet. Undersökningar har visat att en typisk ishall i Sverige använder ca 1 000 MWh per år. Data från de mest effektiva ishallarna har visat att en väl utformad ishall kan nå en energiförbrukning på mindre än 500 MWh per år, vilket ger en stor potential för energisparande åtgärder. En statistisk studie av ett stort antal ishallar i Sverige har visat att kylsystemet har den största andelen av den totala energianvändningen i en ishall, motsvarande 43% i genomsnitt. Kylsystemets energianvändning är kraftigt beroende av olika värmebelastningar på isytan. Tidigare studier har fastställt andelarna i den totala värmebelastningen i ishallar som visat att de värmelaster som uppstår vid avspolning av isytan motsvarar mellan 14-17% av den totala värmelasten. I denna undersökning har spolvattnets volym och temperatur utvärderats med insamlad data genom experimentella mätningar och analyserats vidare med målet att bestämma andelen i totala värmbelastningen och föreslå energisparande åtgärder. Resultaten av studien bygger på data som samlats in i fem olika ishallar i Stockholm, och visar att de flesta fyllningar har en volym mellan 300-500 liter vid en temperatur mellan 30-50°C. Större volymer och högre temperaturer ökar värmebelastningen på isen genom latent och sensibel värme, vilket innebär att mindre volymer och lägre temperaturer minskar värmebelastningen och i sin tur energianvändningen. Undersökningen visar också att energiförbrukningen vid laddning av ismaskinerna varierar och pekar åt att förbrukningen ökar med äldre maskiner. Studien visar att genomsnittliga energiförbrukningen för de fem ishallarna vid en avspolning är 18 kWh i en hall med 100% värmeåtervinning (18% till laddning av ismaskin och 82% till kylsystemets kompressor) och 36 kWh utan värmeåtervinning (9% till laddning av ismaskin, 49% uppvärmning av spolvatten och 42% till kylsystemets kompressor), vilket indikerar en besparing i energiförbrukning genom integrerat värmeåtervinningssystem. Andelen av den totala värmelasten från mätningar visar att i genomsnitt 11% av totala värmebelastningen uppstår på grund av avspolningar. Resultaten har visat att vattentemperaturen vid utloppet av tanken skiljer sig avsevärt från fyllningstemperaturen. Detta innebär att den önskade spolvattentemperaturen skiljer sig från vad som faktiskt läggs på isen. I sin tur innebär det en stor energiförlust mellan 7 000-14 000 kWh / säsong för de undersökta ishallarna.Ice rink operations require significant amounts of energy. It has been concluded that a typical single sheet ice rink in Sweden uses around 1 000 MWh per year. Data from the most efficient ice rinks has shown that a well-designed ice rink could reach an energy usage of less than 500 MWh per year, which leaves a great potential for energy saving actions. A statistical study of a large number of ice rinks in Sweden has shown that the refrigeration system has the largest share of the total energy usage in an ice rink, corresponding to 43% in average. The energy consumption of the refrigeration system is depending on various heat loads on the ice surface. Previous studies has determined the shares of the total heat load in ice rinks, concluding that one of the four largest heat loads in an ice rink comes from the ice resurfacing, corresponding to 14-17%. Floodwater volume and temperature has been evaluated by collecting data through experimental measurements and further analysed with the goal to find energy saving actions. The results of the study are based on data collected in five different ice rinks in Stockholm, Sweden and shows that most fillings of resurfacing machines has a volume between 300-500 litres at a temperature between 30-50°C. Larger volumes and higher temperatures increase the heat load on the ice surface through latent and sensible heat, which means that smaller volumes and lower temperatures decrease the energy consumption. It has also been concluded that older resurfacing machines are larger energy consumers compared with newer models. The study shows that the energy consumption for an average resurfacing process 18 kWh with 100% heat recovery (18% from charging and 82% compressor electricity) and 36 kWh without heat recovery (9% from charging, 49% heating electricity and 42% compressor electricity), which indicates a decrease in energy consumption in ice rinks with heat recovery. The resurfacing share of the total heat loads from the measurements show that in average 11% of the heat load occurs by ice resurfacings. The results have shown that the water temperature at the outlet of the tank differs substantially from the filling temperature. This means that the desired floodwater temperature is different from what you actually get and there is a large waste in energy consumption for heating as the desired resurfacing temperature is rarely achieved. Studies show an approximate waste in energy consumption between 7 000 - 14 000 kWh/season.
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Sherburn, Jesse Andrew. "HYDRODYNAMIC MODELING OF IMPACT CRATERS IN ICE." MSSTATE, 2008. http://sun.library.msstate.edu/ETD-db/theses/available/etd-11052007-091023/.
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In this study, impact craters in water ice are modeled using the hydrodynamic code CTH. In order to capture impact craters in ice an equation of state and a material model are created and validated. The validation of the material model required simulating the Split Pressure Hopkinson Bar (SPHB) experimental apparatus. The SPHB simulation was first compared to experiments completed on Al 6061-T6, then the ice material model was validated. After validation, the cratering simulations modeled known experiments found in the literature. The cratering simulations captured the bulk physical aspects of the experimental craters, and the differences are described. Analysis of the crater simulations showed the damaged volume produced by the projectile was proportional to the projectiles momentum. Also, the identification of four different stages in the crater development of ice (contact and compression, initial damage progression, crater shaping, and ejected damaged material) are described.
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Palmer, Michael. "Mechanisms of natural climate change : the little ice age." Thesis, University of Oxford, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.289120.
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Cook, Andrea. "Modelling of brine transport mechanisms in Antarctic sea ice." Master's thesis, Faculty of Engineering and the Built Environment, 2021. http://hdl.handle.net/11427/33605.
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It is evident that the sea ice cycle, from its formation to its melt, is governed by a complex interaction of the ocean, atmosphere and surrounding continents. Once sea water begins to freeze, physical, biological and chemical processes have implications on the evolution of the sea ice morphology [38]. The distinguishing factor between fresh and sea water ice is brine inclusions that get trapped within the ice pores during freezing. Salt inclusions within frozen ice influence the salinity as well as the physical properties of the sea ice [23]. These brine inclusions form part of a dynamic process within the ice characterized by the movement of brine and phase transition which are the foundation of many of its physical properties [23]. Brine removal subsequently begins to occur due to vertical gravity drainage into the underlying ocean water. This study introduces the application of a biphasic model based on the Theory of Porous Media (TPM) which considers a solid phase for the pore structure of the ice matrix as well as a liquid phase for the brine inclusions, respectively. This work explores the use of the TPM framework towards advancing the description and study of the various desalination mechanisms that are significant in aiding the salt flux into the Southern Ocean. This will foster understanding of brine rejection and how it is linked to the porous microstructure of Antarctic sea ice
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Zhang, Shiping. "FEM analysis of in-flight ice break-up." Thesis, McGill University, 2013. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=114560.
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Using a fracture mechanics framework, we present a finite element method to simulate the break-up of 2D ice accreted on the wings of aircraft and the shedding of 3D ice accreted on blades of helicopter. The fully automated ice break-up module is integrated in FENSAP-ICE [1-2], which is an in-flight ice accretion simulation code that solves flow, droplet impingement and ice accretion, in sequence. The 2D and 3D crack propagation packages are developed and validated by comparing with published results for a single edge cracked plate test case and a single edge-notched specimen with three points bending load, respectively. Numerous complicated ice-shapes are analyzed and comparisons are performed with a contemporary fracture mechanics code. Under typical icing and flow conditions, linear elasticity is found to be adequate for ice break-up analysis. For ice accreted on wings, an important finding of this study is that the breaking of ice has a strong dependence on its shape, i.e. under similar aerodynamic loading, some ice shapes fail while others do not. For ice accreted on helicopters, the finding is that the rotational speed of the blade and interface strength between ice and blade material are the major factors governing the ice break-up. The main objective of this work is to analyze complex multi-physics phenomenon and provide a simplified ice break-up model for the industrial users and aerodynamic designers. The potential use of this tool, however, is not limited to aerodynamics; it can be applied in areas of environmental science, material science, glaciology, earthquake and rupture analysis.Dans le cadre de la mécanique des fractures, nous présentons une méthode d'éléments finis qui simule le bris de la glace accumulée sur les ailes d'avions, en deux dimensions, ainsi que le délestage du givre accumulé sur les pales de l'hélicoptère, en trois dimensions. Le module de bris de glace, entièrement automatisé, est intégré en FENSAP-ICE [1-2], un logiciel de simulation qui résout séquenciellement le flux, l'impact des gouttelettes et le cumul de glace. Les modules bidimensionnels et tridimensionnels de propagation de fissures sont développés et validés par comparaison avec des résultats expérimentaux sur une plaque fissurée d'un seul côté, ainsi que pour un spécimen entaillé d'un seul côté avec une charge de flexion en trois points. Plusieurs formes de glace sont analysées et des comparaisons faites avec un autre code traitant la mécanique des fractures. Dans des conditions typiques de givrage et d'écoulement, l'élasticité linéaire s'est avérée adéquate pour une analyse du bris de glace. Pour la glace accumulée sur les ailes, une conclusion importante de cette étude est que le bris de glace dépend fortement de sa forme, c'est-à-dire que pour des charges aérodynamiques similaires, certaines formes de glace briseront, tandis que d'autres ne le feront pas. En ce qui concerne la glace accumulée sur les hélicoptères, il a été conclu que les facteurs les plus importants pour le bris de glace sont la vitesse rotationnelle de la pale et la force d'adhésion entre la glace et la pale. L'objectif principal de cet ouvrage est d'analyser des phénomènes multi-physiques complexes et de fournir un modèle simplifié du bris de la glace pour les utilisateurs industriels et les concepteurs en aéronautique. L'utilisation de cet outil n'est toutefois pas limitée à l'aérodynamique, puisqu'il peut être employé dans des domaines tels que les sciences environnementales, les sciences des matériaux, la glaciologie et l'analyse des tremblements de terre et de rupture.