Stabilité hydro-mécanique d'un couvert de glace encore solide

1976 ◽  
Vol 3 (1) ◽  
pp. 1-10
Author(s):  
B. Michel ◽  
R. Abdelnour
Keyword(s):  
Froude Number ◽  
Ice Cover ◽  
Water Levels ◽  
Scale Model ◽  
Dimensionless Numbers ◽  
Exponential Relationship ◽  
Retaining Structure ◽  
Break Up ◽  
The Stability ◽  
Hydraulics Laboratory

An experimental study has been made on a scale model of a rectangular canal in the hydraulics laboratory of Laval University in order to simulate the destruction of a solid continuous ice cover under the effect of the tangential forces created by the flow.The canal was 6 ft (1.8 m) wide and 46 ft (14 m) long. At the lower end, an ice retention structure of reticular form was built. The ice was simulated with a wax poured in a continuous and uniform layer; whose properties correspond to that of natural ice at an average scale of 1/25. Ice covers corresponding to thicknesses of 8 to 20 in. (20.3 to 50.8 cm) were simulated at that scale.Tests consisted essentially in increasing progressively the discharge feeding the canal until complete failure of the ice cover and accumulation of the pieces in front of the grid retaining structure.Three important phenomena have been observed and measured. By chronological order the first one is the submersion of the frontal edge of the cover. This happens at a relatively constant Froude number but much higher than the one characterizing the stability of unconsolidated ice jams.An increase in discharge makes the ice cover unstable as it oscillates in the flow. This state is followed closely by the failure of the cover, the movement of the pieces with the flow and their accumulation in front of the retaining structure where they form a dry jam. This phenomenon of failure of the ice cover could be interpreted in the first approximation with two dimensionless numbers one being the Froude number and the other characterizing the ratio of failure forces to gravity forces. We have found that an exponential relationship relates these two numbers and the correlation coefficient for the 25 tests is satisfactory.Finally, we have measured the thrust exerted by the dry jams on the ice retaining structure. There is a very direct hydrostatic relationship between the thrust and flow conditions with a dry jam.These laboratory results are interesting to assess the discharges and water levels required in rivers to break-up ice covers of various resistances. One can estimate these conditions for the case of weakened ice covers before spring break-up. However, more importantly, it is possible to approximate the worst conditions of flooding with an early break-up towards the end of the winter when the ice still has its maximum strength.

Influence of the proposed Site C hydroelectric project on the ice regime of the Peace River

2015 ◽  
Vol 42 (9) ◽  
pp. 645-655 ◽  
Author(s):  
Martin Jasek ◽  
Amy Pryse-Phillips
Keyword(s):  
Clean Energy ◽  
Ice Cover ◽  
Water Levels ◽  
River Ice ◽  
Hydroelectric Project ◽  
Peace River ◽  
Ice Conditions ◽  
Break Up ◽  
Hydro Project ◽  
The Town

The objectives of the study were to describe the existing ice conditions in the Peace River and to predict changes as a result of the proposed Site C Clean Energy Project (the Project). The analyses of changes due to the Project were conducted using the CRISSP and PRTIGM models. Sixteen winters were simulated to provide a representative range of meteorological conditions on which to base the conclusions of the study. Potential changes are described in terms of the following ice characteristics: maximum upstream extent of ice cover; timing of ice cover formation and break-up; freeze-up and break-up water levels at the Town of Peace River; ice thickness; changes in ice conditions relevant for river ice crossings. The analyses also included predicting changes in these ice characteristics due to the combined influence of the Project and the proposed Dunvegan Hydro Project in Alberta. Two future climate scenarios were also considered.

scholarly journals Sea ice and the stability of north and northeast Greenland floating glaciers

2001 ◽  
Vol 33 ◽  
pp. 474-480 ◽  
Author(s):  
Niels Reeh ◽  
Henrik Højmark Thomsen ◽  
Anthony K. Higgins ◽  
Anker Weidick
Keyword(s):  
Sea Ice ◽  
Ice Cover ◽  
Aerial Photographs ◽  
The Arctic ◽  
The North ◽  
Glacier Ice ◽  
Ice Conditions ◽  
Fast Ice ◽  
Break Up ◽  
The Stability

AbstractThe interaction between sea ice and glaciers has been studied for the floating tongue of Nioghalvfjerdsfjorden glacier, northeast Greenland (79°30’N, 22° W). Information from glacial geological studies, expedition reports, aerial photographs and satellite imagery is used to document the glacier front position and fast-ice conditions on millennial to decadal time-scales. The studies indicate that the stability of the floating glacier margin is dependent on the presence of a protecting fast-ice cover in front of the glacier. In periods with a permanent fast-ice cover, no calving occurs, but after fast-ice break-up the glacier responds with a large calving activity, whereby several years of accumulated glacier-ice flux suddenly breaks away. Climate-induced changes of sea-ice conditions in the Arctic Ocean with seasonal break-up of the near-shore fast ice could lead to disintegration of the floating glaciers. The present dominant mass loss by bottom melting would then to a large extent be taken over by grounding-line calving of icebergs. The local influx of fresh water from the north Greenland glaciers to the sea would be reduced and the local iceberg production would increase.

scholarly journals Spatial-Temporal Distribution of the Freeze–Thaw Cycle of the Largest Lake (Qinghai Lake) in China Based on Machine Learning and MODIS from 2000 to 2020

2021 ◽  
Vol 13 (9) ◽  
pp. 1695
Author(s):  
Weixiao Han ◽  
Chunlin Huang ◽  
Juan Gu ◽  
Jinliang Hou ◽  
Ying Zhang
Keyword(s):  
Machine Learning ◽  
Land Surface ◽  
Temporal Dynamics ◽  
Temporal Distribution ◽  
Ice Cover ◽  
Qinghai Lake ◽  
Gap Filling ◽  
Thaw Cycle ◽  
Break Up ◽  
Ice Phenology

The lake ice phenology variations are vital for the land–surface–water cycle. Qinghai Lake is experiencing amplified warming under climate change. Based on the MODIS imagery, the spatio-temporal dynamics of the ice phenology of Qinghai Lake were analyzed using machine learning during the 2000/2001 to 2019/2020 ice season, and cloud gap-filling procedures were applied to reconstruct the result. The results showed that the overall accuracy of the water–ice classification by random forest and cloud gap-filling procedures was 98.36% and 92.56%, respectively. The annual spatial distribution of the freeze-up and break-up dates ranged primarily from DOY 330 to 397 and from DOY 70 to 116. Meanwhile, the decrease rates of freeze-up duration (DFU), full ice cover duration (DFI), and ice cover duration (DI) were 0.37, 0.34, and 0.13 days/yr., respectively, and the duration was shortened by 7.4, 6.8, and 2.6 days over the past 20 years. The increased rate of break-up duration (DBU) was 0.58 days/yr. and the duration was lengthened by 11.6 days. Furthermore, the increase in temperature resulted in an increase in precipitation after two years; the increase in precipitation resulted in the increase in DBU and decrease in DFU in corresponding years, and decreased DI and DFI after one year.

scholarly journals THE BEHAVIOR CHARACTERISTICS OF A RESERVOIR LEVEE SUBJECTED TO INCREASING WATER LEVELS

2017 ◽  
Vol 23 (1) ◽  
pp. 15-27
Author(s):  
Chung-Won LEE ◽  
Yong-Seong KIM ◽  
Sung-Yong PARK ◽  
Dong-Gyun KIM ◽  
Gunn HEO
Keyword(s):  
Hydraulic Fracturing ◽  
Real Time ◽  
Pore Water ◽  
Volumetric Strain ◽  
Water Levels ◽  
The Core ◽  
The Stability ◽  
Centrifugal Model ◽  
Behavior Characteristics ◽  
Plastic Volumetric Strain

Centrifugal model testing has been widely used to study the stability of levees. However, there have been a limited number of physical studies on levees where the velocity of increasing water levels was considered. To investigate the behavior characteristics of reservoir levees with different velocities of increasing water levels, centrifugal model tests and seepage-deformation coupled analyses were conducted. Through this study, it was confirmed that increasing water levels at higher velocities induces dramatic increases in the displacement, plastic volumetric strain and risk of hydraulic fracturing occurring in the core of the levee. Hence, real-time monitoring of the displacement and the pore water pres­sure of a levee is important to ensure levee stability.

scholarly journals Toward continental hydrologic–hydrodynamic modeling in South America

2018 ◽  
Vol 22 (9) ◽  
pp. 4815-4842 ◽  
Author(s):  
Vinícius A. Siqueira ◽  
Rodrigo C. D. Paiva ◽  
Ayan S. Fleischmann ◽  
Fernando M. Fan ◽  
Anderson L. Ruhoff ◽  
...  
Keyword(s):  
South America ◽  
Land Surface ◽  
River Discharge ◽  
Hydrological Modeling ◽  
Water Levels ◽  
Scale Model ◽  
Global Models ◽  
Discharge Data ◽  
Continental Scale ◽  
Terrestrial Water

Abstract. Providing reliable estimates of streamflow and hydrological fluxes is a major challenge for water resources management over national and transnational basins in South America. Global hydrological models and land surface models are a possible solution to simulate the terrestrial water cycle at the continental scale, but issues about parameterization and limitations in representing lowland river systems can place constraints on these models to meet local needs. In an attempt to overcome such limitations, we extended a regional, fully coupled hydrologic–hydrodynamic model (MGB; Modelo hidrológico de Grandes Bacias) to the continental domain of South America and assessed its performance using daily river discharge, water levels from independent sources (in situ, satellite altimetry), estimates of terrestrial water storage (TWS) and evapotranspiration (ET) from remote sensing and other available global datasets. In addition, river discharge was compared with outputs from global models acquired through the eartH2Observe project (HTESSEL/CaMa-Flood, LISFLOOD and WaterGAP3), providing the first cross-scale assessment (regional/continental  ×  global models) that makes use of spatially distributed, daily discharge data. A satisfactory representation of discharge and water levels was obtained (Nash–Sutcliffe efficiency, NSE > 0.6 in 55 % of the cases) and the continental model was able to capture patterns of seasonality and magnitude of TWS and ET, especially over the largest basins of South America. After the comparison with global models, we found that it is possible to obtain considerable improvement on daily river discharge, even by using current global forcing data, just by combining parameterization and better routing physics based on regional experience. Issues about the potential sources of errors related to both global- and continental-scale modeling are discussed, as well as future directions for improving large-scale model applications in this continent. We hope that our study provides important insights to reduce the gap between global and regional hydrological modeling communities.

scholarly journals Scaling for lobe and cleft patterns in particle-laden gravity currents

2013 ◽  
Vol 20 (1) ◽  
pp. 121-130 ◽  
Author(s):  
A. Jackson ◽  
B. Turnbull ◽  
R. Munro
Keyword(s):  
Granular Material ◽  
Froude Number ◽  
Particle Diameter ◽  
Granular Flows ◽  
Leading Edge ◽  
Air Entrainment ◽  
Gravity Currents ◽  
Laboratory Scale ◽  
Scale Model ◽  
Snow Avalanches

Abstract. Lobe and cleft patterns are frequently observed at the leading edge of gravity currents, including non-Boussinesq particle-laden currents such as powder snow avalanches. Despite the importance of the instability in driving air entrainment, little is known about its origin or the mechanisms behind its development. In this paper we seek to gain a better understanding of these mechanisms from a laboratory scale model of powder snow avalanches using lightweight granular material. The instability mechanisms in these flows appear to be a combination of those found in both homogeneous Boussinesq gravity currents and unsuspended granular flows, with the size of the granular particles playing a central role in determining the wavelength of the lobe and cleft pattern. When scaled by particle diameter a relationship between the Froude number and the wavelength of the lobe and cleft pattern is found, where the wavelength increases monotonically with the Froude number.

Lake ice phenology changes in the northern hemisphere

2021 ◽  
Author(s):  
Yubao Qiu ◽  
Xingxing Wang ◽  
Matti Leppäranta ◽  
Bin Cheng ◽  
Yixiao Zhang
Keyword(s):  
Remote Sensing ◽  
North America ◽  
Northern Hemisphere ◽  
Ice Cover ◽  
Passive Microwave ◽  
Lake Area ◽  
Lake Ice ◽  
Northern Tibetan Plateau ◽  
Break Up ◽  
Ice Phenology

<p>Lake-ice phenology is an essential indicator of climate change impact for different regions (Livingstone, 1997; Duguay, 2010), which helps understand the regional characters of synchrony and asynchrony. The observation of lake ice phenology includes ground observation and remote sensing inversion. Although some lakes have been observed for hundreds of years, due to the limitations of the observation station and the experience of the observers, ground observations cannot obtain the lake ice phenology of the entire lake. Remote sensing has been used for the past 40 years, in particular, has provided data covering the high mountain and high latitude regions, where the environment is harsh and ground observations are lacking. Remote sensing also provides a unified data source and monitoring standard, and the possibility of monitoring changes in lake ice in different regions and making comparisons between them. The existing remote sensing retrieval products mainly cover North America and Europe, and data for Eurasia is lacking (Crétaux et al., 2020).</p><p>Based on the passive microwave, the lake ice phenology of 522 lakes in the northern hemisphere during 1978-2020 was obtained, including Freeze-Up Start (FUS), Freeze-Up End (FUE), Break-Up Start (BUS), Break-Up End (BUE), and Ice Cover Duration (ICD). The ICD is the duration from the FUS to the BUE, which can directly reflect the ice cover condition. At latitudes north of 60°N, the average of ICD is approximately 8-9 months in North America and 5-6 months in Eurasia. Limited by the spatial resolution of the passive microwave, lake ice monitoring is mainly in Northern Europe. Therefore, the average of ICD over Eurasia is shorter, while the ICD is more than 6 months for most lakes in Russia. After 2000, the ICD has shown a shrinking trend, except northeastern North America (southeast of the Hudson Bay) and the northern Tibetan Plateau. The reasons for the extension of ice cover duration need to be analyzed with parameters, such as temperature, the lake area, and lake depth, in the two regions.</p>

Stability of Heat Pipes in Vapor-Dominated Systems

1999 ◽  
Author(s):  
Pouya Amili ◽  
Yanis C. Yortsos
Keyword(s):  
Rayleigh Number ◽  
Linear Stability ◽  
Oil Recovery ◽  
Critical Rayleigh Number ◽  
Stability Limit ◽  
Wave Number ◽  
Nuclear Waste Repository ◽  
Geothermal Systems ◽  
Dimensionless Numbers ◽  
The Stability

Abstract We study the linear stability of a two-phase heat pipe zone (vapor-liquid counterflow) in a porous medium, overlying a superheated vapor zone. The competing effects of gravity, condensation and heat transfer on the stability of a planar base state are analyzed in the linear stability limit. The rate of growth of unstable disturbances is expressed in terms of the wave number of the disturbance, and dimensionless numbers, such as the Rayleigh number, a dimensionless heat flux and other parameters. A critical Rayleigh number is identified and shown to be different than in natural convection under single phase conditions. The results find applications to geothermal systems, to enhanced oil recovery using steam injection, as well as to the conditions of the proposed Yucca Mountain nuclear waste repository. This study complements recent work of the stability of boiling by Ramesh and Torrance (1993).

Spraying Experiments with a Model Stern Trawler

1998 ◽  
Vol 42 (04) ◽  
pp. 260-265 ◽  
Author(s):  
K. K. Chung ◽  
E. P. Lozowski ◽  
W. P. Zakrzewski ◽  
R. Gagnon ◽  
T. Thompson
Keyword(s):  
Statistical Analysis ◽  
Froude Number ◽  
Significant Wave Height ◽  
Flux Distribution ◽  
Full Scale ◽  
Scale Model ◽  
Spray Droplet ◽  
Towing Tank ◽  
Ship Speed ◽  
Longitudinal Distance

With a view to formulating vessel spraying and icing models, 22 spraying experiments were performed in the IMD/NRC towing tank using a 1:13 scale model of the stern trawler MT Zandberg. Neglecting the effect of wind drag on the spray droplet trajectories, an empirical spray flux equation for the scale Zandberg was derived, based on a statistical analysis of the spraying data. Using Froude number scaling, this model-scale equation was transformed into a full-scale spray flux equation. This spraying study shows that the total spray flux generated during ship/wave collisions depends on ship speed (Vs) and significant wave height (H1/3) according to V3⅓, H7⅓ while the spray flux distribution over the foredeck varies exponentially with longitudinal distance. Using this full-scale spray flux equation, a spray trajectory model, taking wind drag effects into account, was subsequently developed.

scholarly journals Experimental Study on City Road Collapse under Vibrating Load

2020 ◽  
Vol 2020 ◽  
pp. 1-13
Author(s):  
Yuxiao Wang ◽  
Gang Shi ◽  
Xiaowei Tian ◽  
Chaoyue Li ◽  
Huanyu Cheng
Keyword(s):  
Dynamic Load ◽  
Static Load ◽  
Soil Layer ◽  
Formation Time ◽  
Traffic Load ◽  
Scale Model ◽  
The Road ◽  
Ultimate Failure ◽  
The Stability ◽  
Collapse Process

Underground pipeline seepage and traffic load are the important factors causing city road collapse. In this paper, eight groups of indoor scale model experiments are used to study the road collapse caused by pipeline seepage, taking into account the load type, pipeline buried depth, the distance between pipeline and loss channel, the relative position of pipeline and loss channel, and the formation time of loss channel. The results show that when the erosion channel was formed later, the underlying erosion cavity was ellipsoid, while the other erosion cavities were funnel shaped. When only the static load is applied, the time to reach the ultimate failure is longer than that when only dynamic load is applied. The smaller dynamic load can increase the stability of the soil above the seepage pipeline, while the larger dynamic load can accelerate the collapse process. With the formation time of the erosion channel increasing, the erosion void size is larger and the surface is easier to collapse. With the increase of the distance between the loss passage and the pipeline, the damage time of the road surface is also increased. The larger the thickness of the soil layer above the pipeline, the smaller the size of the underground cavity and the surface subsidence.

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