A Model Study of Powder-Snow Avalanches
Abstract A powder-snow avalanche is a particular type of turbulent gravity current which it is proposed to treat using methods developed in contexts where the Boussinesq approximation is valid. Hence, it is assumed that the air entrainment rate E primarily depends on the internal Froude number (Toch...
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Cambridge University Press (CUP)
1977
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Online Access: | http://dx.doi.org/10.1017/s0022143000029373 https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0022143000029373 |
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crcambridgeupr:10.1017/s0022143000029373 2024-03-03T08:46:05+00:00 A Model Study of Powder-Snow Avalanches Hopfinger, E. J. Tochon-Danguy, J.-C. 1977 http://dx.doi.org/10.1017/s0022143000029373 https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0022143000029373 en eng Cambridge University Press (CUP) Journal of Glaciology volume 19, issue 81, page 343-356 ISSN 0022-1430 1727-5652 Earth-Surface Processes journal-article 1977 crcambridgeupr https://doi.org/10.1017/s0022143000029373 2024-02-08T08:41:37Z Abstract A powder-snow avalanche is a particular type of turbulent gravity current which it is proposed to treat using methods developed in contexts where the Boussinesq approximation is valid. Hence, it is assumed that the air entrainment rate E primarily depends on the internal Froude number (Tochon-Danguy and Hopfinger, [1975]) and that the large density variation in an avalanche reduces only the drag resulting from the air entrainment. In order for this drag to dominate over the wall stress it is necessary that the slope angle be greater than a certain minimum value which depends on the density ratio of the flow. For a low-density flow, for example, a minimum slope angle of about 5° is necessary. The more unusual aspect is that an avalanche may also entrain snow along its path which increases its mass and can produce in certain cases an accelerating flow. This aspect is included in the theoretical treatment. Experiments have been carried out in an inclined water channel using brine as dense fluid. Visual observations as well as measurements of the velocity and density profiles have been made. Various states of flow are proposed depending on whether the avalanche is “long" (having the structure of a usual gravity current) or “short" (having the structure of a thermal) or whether snow is entrained. The practical consequences which can be drawn from these results are discussed, in particular in the context of the design of defence structures, and flow visualizations of a gravity current impinging on an obstacle give an idea of the protected region. Article in Journal/Newspaper Journal of Glaciology Cambridge University Press Journal of Glaciology 19 81 343 356 |
institution |
Open Polar |
collection |
Cambridge University Press |
op_collection_id |
crcambridgeupr |
language |
English |
topic |
Earth-Surface Processes |
spellingShingle |
Earth-Surface Processes Hopfinger, E. J. Tochon-Danguy, J.-C. A Model Study of Powder-Snow Avalanches |
topic_facet |
Earth-Surface Processes |
description |
Abstract A powder-snow avalanche is a particular type of turbulent gravity current which it is proposed to treat using methods developed in contexts where the Boussinesq approximation is valid. Hence, it is assumed that the air entrainment rate E primarily depends on the internal Froude number (Tochon-Danguy and Hopfinger, [1975]) and that the large density variation in an avalanche reduces only the drag resulting from the air entrainment. In order for this drag to dominate over the wall stress it is necessary that the slope angle be greater than a certain minimum value which depends on the density ratio of the flow. For a low-density flow, for example, a minimum slope angle of about 5° is necessary. The more unusual aspect is that an avalanche may also entrain snow along its path which increases its mass and can produce in certain cases an accelerating flow. This aspect is included in the theoretical treatment. Experiments have been carried out in an inclined water channel using brine as dense fluid. Visual observations as well as measurements of the velocity and density profiles have been made. Various states of flow are proposed depending on whether the avalanche is “long" (having the structure of a usual gravity current) or “short" (having the structure of a thermal) or whether snow is entrained. The practical consequences which can be drawn from these results are discussed, in particular in the context of the design of defence structures, and flow visualizations of a gravity current impinging on an obstacle give an idea of the protected region. |
format |
Article in Journal/Newspaper |
author |
Hopfinger, E. J. Tochon-Danguy, J.-C. |
author_facet |
Hopfinger, E. J. Tochon-Danguy, J.-C. |
author_sort |
Hopfinger, E. J. |
title |
A Model Study of Powder-Snow Avalanches |
title_short |
A Model Study of Powder-Snow Avalanches |
title_full |
A Model Study of Powder-Snow Avalanches |
title_fullStr |
A Model Study of Powder-Snow Avalanches |
title_full_unstemmed |
A Model Study of Powder-Snow Avalanches |
title_sort |
model study of powder-snow avalanches |
publisher |
Cambridge University Press (CUP) |
publishDate |
1977 |
url |
http://dx.doi.org/10.1017/s0022143000029373 https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0022143000029373 |
genre |
Journal of Glaciology |
genre_facet |
Journal of Glaciology |
op_source |
Journal of Glaciology volume 19, issue 81, page 343-356 ISSN 0022-1430 1727-5652 |
op_doi |
https://doi.org/10.1017/s0022143000029373 |
container_title |
Journal of Glaciology |
container_volume |
19 |
container_issue |
81 |
container_start_page |
343 |
op_container_end_page |
356 |
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1792501949686349824 |