Eloïse Bovet - Academia.edu (original) (raw)
Papers by Eloïse Bovet
The purpose of this paper is to describe the snow avalanche dynamics empha-sizing the phenomenon ... more The purpose of this paper is to describe the snow avalanche dynamics empha-sizing the phenomenon of entrainment, the shape variation and the velocity profile thank to the peculiar features of the Non-Newtonian fluids, in par-ticular those showing shear thinning and Bingham constitutive behaviour. The model is general in its present form, and could eventually be extended to specific granular flow. Two different approaches are proposed to simulate the avalanches numerically: the determination of the relations to transform the avalanche domain in a simple shape domain that doesn't change in time and the level set method, suitable for the free boundary problems. Finally, the characteristics of the variation of the interface between avalanche and snowcover under a similarity hypothesis is put forward. A further refinement of those methodologies, coupled with experimental data, will eventually allow to validate the model proposed.
TO) – Italy; 3 Fondazione Montagna Sicura -Montagne Sûre, Courmayeur (AO) – Italy; 4 Struttura as... more TO) – Italy; 3 Fondazione Montagna Sicura -Montagne Sûre, Courmayeur (AO) – Italy; 4 Struttura assetto idrogeologico dei bacini montani – Ufficio Neve e Valanghe, Regione Autonoma Valle d'Aosta, Quart (AO) -Italy; . ABSTRACT: A new test site devoted to the measurement of the effects of snow-gliding on active de-fense structures has been conceived and built in Aosta Valley, north-western Italian Alps. The core of the experimental test site is represented by an instrumented snow-umbrella, a semi-flexible snow retaining device composed of a flexible net panel supported by a rigid metallic frame, and by a set of instrumented glide shoes for the evaluation of downhill snowpack motion. Snow/soil interface temperature and moisture sensors and an automatic weather station, surround the main apparatus allowing the recording of the environmental conditions onsite. After a detailed description of the instrumentation, the paper stresses on the integrated approach, which presupposes to combi...
5 Assetto idrogeologico dei bacini montani – Ufficio Neve e Valanghe della Regione autonoma Valle... more 5 Assetto idrogeologico dei bacini montani – Ufficio Neve e Valanghe della Regione autonoma Valle d'Aosta, Quart (AO) – Italy Numerical avalanche dynamics models are widely used to calculate extreme avalanches for hazard mapping and mitigation measure planning. A basic model input is the terrain represented by Digital Elevation Models (DEM). Usually summer topography is used as model input, even though most ava-lanches run on snow-covered terrain with filled gullies and smoothed roughness. Moreover, the depos-its of previous avalanche events can significantly influence the dynamics of following events, espe-cially considering frequent avalanches on the same path. The aim of this paper is to analyze the outputs of the avalanche dynamics model RAMMS obtained using DEM input from summer compared to Digital Surface Model (DSM) generated in winter by laser scanning and digital photogrammetry. We use the 2D model RAMMS to calculate avalanches in two study areas: Seehore test site in A...
ABSTRACT Within the Operational programme 'Italy -France (Alps -ALCOTRA) &#39... more ABSTRACT Within the Operational programme 'Italy -France (Alps -ALCOTRA) 'Project "DynAval -Dynamique des avalanches: départ et interactions écoulement/obstacles" the experimental avalanche test site "P.ta Seehore" is operative within the Monterosa Ski resort in the Aosta Valley (northwestern Italian Alps). The main goal of the project in 2010 was calibrating in laboratory, installing and testing on site the instrumented obstacle previously designed, to measure impact forces of the avalanches, and going on to survey on site the artificially triggered avalanches. The correct position of the obstacle was determined thanks to the experiments carried out during winter 2009/2010 and the available historical data; therefore in summer 2010 the concrete foundation of the mast was built, above which the instrumented obstacle was installed in autumn 2010. The galvanized steel obstacle is composed of two masts of about 4 m of height supporting 5 instrumented hori-zontal plates that measure the impact forces of the avalanches; in particular, the data are registered by 10 loading cells, 4 accelerometers, 4 thermocouples and a pressure transducer. The on-board transducers and data logger are remotely operated via an optical fiber connection with a computer located in a control room located in a safe and comfortable location accessible in all weather conditions. Even if most of the avalanches are artificially triggered (Daisy-bell and Carica Vassale), the system records also natural events. Previously, for the structural identification of the mast, many dynamic and static laboratory tests were performed in order to calibrate FEM numerical models. To evaluate the erosion, deposition and the front velocity, laser scanner measurements and multi-picture analysis are performed. In order to define a benchmark network, three reference points were installed in the site and several natural benchmarks were located and measured on the slope by a GPS-RTK survey, assuring centimetric precision in positioning. To detect physical and mechanical snow properties in the release, track and deposition zones, filed surveys are performed. The perimeter of the avalanche is outlined by using GPS devices coupled with snow depth measurements. Thanks to the installed instrumentation and surveys performed during Winter 2010/2011, the first available data are presented.
The purpose of this work, within the Project "DynAval-Dynamique des avalanches: départ et interac... more The purpose of this work, within the Project "DynAval-Dynamique des avalanches: départ et interactions écoulement/obstacles"-European Territorial Cooperation objective Italy-France (Alps), is to analyse the effects of the snow avalanche impact against structures by the comparison of a real case study with simulations. By a back analysis of the damages occurred on 15 December 2008 in Aosta Valley (North West of Italy), and more precisely in the village Les Thoules in Valsavaranche, the impact pressure is estimated. In this event 12 houses are destroyed or damaged, as well as electric poles, trees and an high voltage pylon. A first simplified attempt of simulation of the impact area is consequently proposed. The avalanche behaviour, considered as an incompressible fluid, is described by a twodimensional, in the avalanche slope, Navier-Stokes equations to which an advection equation is coupled to take into account the shape variation. A two dimensional and a three dimensional stationary models are implemented too. The models allow to describe the velocity and the pressure at every point. The role played by the natural dam localised in the site of protecting the down-wind structures is analysed. In addition, the pressure acting on the different parts of the houses is investigated, proposing different Cp coefficients, in order to evaluate which parts should have been more resistant. Finally, since the objects involved had different shapes and dimensions, an investigation into the Cd coefficient is made. Finally, the capabilities and the deficiencies of the models proposed are shown.
ABSTRACT In this paper, the level set method, suitable for free boundary problems, is applied to ... more ABSTRACT In this paper, the level set method, suitable for free boundary problems, is applied to snow avalanches. To this aim, the system constituted by air and avalanche is considered as a domain composed by two fluids having different densities and viscosities. In particular a shear thinning fluid-like constitutive behavior is assumed for snow as well as a Newtonian one. Simulations show, for instance, the transport of avalanche mass towards the head and that the head of the avalanche is faster than its tail, as confirmed by experimental observations. An important aspect is that this model allows to describe the shape variation, the velocity and the pressure, outputs of fundamental importance to describe correctly the interaction between the avalanches and the structures located along the avalanche path. In conclusion, although these results are still qualitative, they confirm that the proposed method can be adequately refined to describe the real behaviour of avalanches.
Meccanica, 2009
The purpose of this paper is to develop a model to describe the snow avalanche dynamics emphasizi... more The purpose of this paper is to develop a model to describe the snow avalanche dynamics emphasizing the phenomenon of entrainment, the shape variation and the velocity profile thanks to the peculiar features of non-Newtonian fluids, in particular those showing shear thinning and Bingham-like constitutive behaviours. Two different approaches are proposed to simulate the avalanches numerically. The first considers the transformation of the avalanche domain into a simple shape domain that does not change in time. The second is based on the level set method, which is suitable for free boundary problems. Finally, the characteristics of the variation of the interface between avalanche and snowcover under a similarity hypothesis is put forward. The model is validated through the comparison with some experimental data.
Cold Regions Science and Technology, 2013
(AAM) is copyrighted and published by Elsevier. It is posted here by agreement between Elsevier a... more (AAM) is copyrighted and published by Elsevier. It is posted here by agreement between Elsevier and the University of Turin. Changes resulting from the publishing process-such as editing, corrections, structural formatting, and other quality control mechanisms-may not be reflected in this version of the text. The definitive version of the text was subsequently published in COLD REGIONS SCIENCE AND TECHNOLOGY, 86, 2013, 10.1016/j.coldregions.2012.10.014. You may download, copy and otherwise use the AAM for non-commercial purposes provided that your license is limited by the following restrictions: (1) You may use this AAM for non-commercial purposes only under the terms of the CC-BY-NC-ND license. (2) The integrity of the work and identification of the author, copyright owner, and publisher must be preserved in any copy.
Applied Mechanics and Materials, 2011
The paper aims to analyse the e ects of topography and building position on themagnitude of press... more The paper aims to analyse the e ects of topography and building position on themagnitude of pressure exerted by snow avalanches against buildings, through a structural backanalysis and numerical uid-dynamics. Studying a real snow avalanche impact occurred in2008 which destroyed a village in Valsavarenche (Aosta Valley - IT), the attention is focused onthe avalanche ow deviation caused by the destructive interaction with a rst building, whichprotected part of a second building beyond it. By means of photographical and in situ survey,a detailed description of avalanche geometrical, dynamical and physical properties is outlined.A structural investigation, based both on debris arrangement and on measurements on theundamaged parts of buildings is also carried out.Thus, a back analysis is carried out in order to de ne collapse dynamics and to estimate theupper and the lower bound of impact pressure. Afterwards, numerical uid-dynamical analysesare performed to simulate di erent impact scen...
Avalanche risk management assumes an in-depth knowledge of the nivometeorological situation to wh... more Avalanche risk management assumes an in-depth knowledge of the nivometeorological situation to which tools for the definition of avalanche potential release can be associated. The application of the PRA tool, developed by the SLF, on 600 real cases in Aosta Valley showed the important role played by the wind direction in determining scenarios of avalanche detachment. On those basis a rapid method has been developed, using the 10m wind intensity and direction data provided by the Cosmoi2 predictive model. The wind direction input was calculated by averaging vectorially the wind directions over the 24h, weighted with the cube of the intensity. In order to validate this procedure, the data elaborated with our procedure were compared with 1) the data of 52 automatic stations and 2) the observations contained in the Models 1 A.I.NE.VA. Scenarios of possible snow eroded / loaded areas are realized according to the wind direction at both valley and single-basin scales. Daily, after 40 minu...
The purpose of this paper is to describe the snow avalanche dynamics empha-sizing the phenomenon ... more The purpose of this paper is to describe the snow avalanche dynamics empha-sizing the phenomenon of entrainment, the shape variation and the velocity profile thank to the peculiar features of the Non-Newtonian fluids, in par-ticular those showing shear thinning and Bingham constitutive behaviour. The model is general in its present form, and could eventually be extended to specific granular flow. Two different approaches are proposed to simulate the avalanches numerically: the determination of the relations to transform the avalanche domain in a simple shape domain that doesn't change in time and the level set method, suitable for the free boundary problems. Finally, the characteristics of the variation of the interface between avalanche and snowcover under a similarity hypothesis is put forward. A further refinement of those methodologies, coupled with experimental data, will eventually allow to validate the model proposed.
TO) – Italy; 3 Fondazione Montagna Sicura -Montagne Sûre, Courmayeur (AO) – Italy; 4 Struttura as... more TO) – Italy; 3 Fondazione Montagna Sicura -Montagne Sûre, Courmayeur (AO) – Italy; 4 Struttura assetto idrogeologico dei bacini montani – Ufficio Neve e Valanghe, Regione Autonoma Valle d'Aosta, Quart (AO) -Italy; . ABSTRACT: A new test site devoted to the measurement of the effects of snow-gliding on active de-fense structures has been conceived and built in Aosta Valley, north-western Italian Alps. The core of the experimental test site is represented by an instrumented snow-umbrella, a semi-flexible snow retaining device composed of a flexible net panel supported by a rigid metallic frame, and by a set of instrumented glide shoes for the evaluation of downhill snowpack motion. Snow/soil interface temperature and moisture sensors and an automatic weather station, surround the main apparatus allowing the recording of the environmental conditions onsite. After a detailed description of the instrumentation, the paper stresses on the integrated approach, which presupposes to combi...
5 Assetto idrogeologico dei bacini montani – Ufficio Neve e Valanghe della Regione autonoma Valle... more 5 Assetto idrogeologico dei bacini montani – Ufficio Neve e Valanghe della Regione autonoma Valle d'Aosta, Quart (AO) – Italy Numerical avalanche dynamics models are widely used to calculate extreme avalanches for hazard mapping and mitigation measure planning. A basic model input is the terrain represented by Digital Elevation Models (DEM). Usually summer topography is used as model input, even though most ava-lanches run on snow-covered terrain with filled gullies and smoothed roughness. Moreover, the depos-its of previous avalanche events can significantly influence the dynamics of following events, espe-cially considering frequent avalanches on the same path. The aim of this paper is to analyze the outputs of the avalanche dynamics model RAMMS obtained using DEM input from summer compared to Digital Surface Model (DSM) generated in winter by laser scanning and digital photogrammetry. We use the 2D model RAMMS to calculate avalanches in two study areas: Seehore test site in A...
ABSTRACT Within the Operational programme 'Italy -France (Alps -ALCOTRA) &#39... more ABSTRACT Within the Operational programme 'Italy -France (Alps -ALCOTRA) 'Project "DynAval -Dynamique des avalanches: départ et interactions écoulement/obstacles" the experimental avalanche test site "P.ta Seehore" is operative within the Monterosa Ski resort in the Aosta Valley (northwestern Italian Alps). The main goal of the project in 2010 was calibrating in laboratory, installing and testing on site the instrumented obstacle previously designed, to measure impact forces of the avalanches, and going on to survey on site the artificially triggered avalanches. The correct position of the obstacle was determined thanks to the experiments carried out during winter 2009/2010 and the available historical data; therefore in summer 2010 the concrete foundation of the mast was built, above which the instrumented obstacle was installed in autumn 2010. The galvanized steel obstacle is composed of two masts of about 4 m of height supporting 5 instrumented hori-zontal plates that measure the impact forces of the avalanches; in particular, the data are registered by 10 loading cells, 4 accelerometers, 4 thermocouples and a pressure transducer. The on-board transducers and data logger are remotely operated via an optical fiber connection with a computer located in a control room located in a safe and comfortable location accessible in all weather conditions. Even if most of the avalanches are artificially triggered (Daisy-bell and Carica Vassale), the system records also natural events. Previously, for the structural identification of the mast, many dynamic and static laboratory tests were performed in order to calibrate FEM numerical models. To evaluate the erosion, deposition and the front velocity, laser scanner measurements and multi-picture analysis are performed. In order to define a benchmark network, three reference points were installed in the site and several natural benchmarks were located and measured on the slope by a GPS-RTK survey, assuring centimetric precision in positioning. To detect physical and mechanical snow properties in the release, track and deposition zones, filed surveys are performed. The perimeter of the avalanche is outlined by using GPS devices coupled with snow depth measurements. Thanks to the installed instrumentation and surveys performed during Winter 2010/2011, the first available data are presented.
The purpose of this work, within the Project "DynAval-Dynamique des avalanches: départ et interac... more The purpose of this work, within the Project "DynAval-Dynamique des avalanches: départ et interactions écoulement/obstacles"-European Territorial Cooperation objective Italy-France (Alps), is to analyse the effects of the snow avalanche impact against structures by the comparison of a real case study with simulations. By a back analysis of the damages occurred on 15 December 2008 in Aosta Valley (North West of Italy), and more precisely in the village Les Thoules in Valsavaranche, the impact pressure is estimated. In this event 12 houses are destroyed or damaged, as well as electric poles, trees and an high voltage pylon. A first simplified attempt of simulation of the impact area is consequently proposed. The avalanche behaviour, considered as an incompressible fluid, is described by a twodimensional, in the avalanche slope, Navier-Stokes equations to which an advection equation is coupled to take into account the shape variation. A two dimensional and a three dimensional stationary models are implemented too. The models allow to describe the velocity and the pressure at every point. The role played by the natural dam localised in the site of protecting the down-wind structures is analysed. In addition, the pressure acting on the different parts of the houses is investigated, proposing different Cp coefficients, in order to evaluate which parts should have been more resistant. Finally, since the objects involved had different shapes and dimensions, an investigation into the Cd coefficient is made. Finally, the capabilities and the deficiencies of the models proposed are shown.
ABSTRACT In this paper, the level set method, suitable for free boundary problems, is applied to ... more ABSTRACT In this paper, the level set method, suitable for free boundary problems, is applied to snow avalanches. To this aim, the system constituted by air and avalanche is considered as a domain composed by two fluids having different densities and viscosities. In particular a shear thinning fluid-like constitutive behavior is assumed for snow as well as a Newtonian one. Simulations show, for instance, the transport of avalanche mass towards the head and that the head of the avalanche is faster than its tail, as confirmed by experimental observations. An important aspect is that this model allows to describe the shape variation, the velocity and the pressure, outputs of fundamental importance to describe correctly the interaction between the avalanches and the structures located along the avalanche path. In conclusion, although these results are still qualitative, they confirm that the proposed method can be adequately refined to describe the real behaviour of avalanches.
Meccanica, 2009
The purpose of this paper is to develop a model to describe the snow avalanche dynamics emphasizi... more The purpose of this paper is to develop a model to describe the snow avalanche dynamics emphasizing the phenomenon of entrainment, the shape variation and the velocity profile thanks to the peculiar features of non-Newtonian fluids, in particular those showing shear thinning and Bingham-like constitutive behaviours. Two different approaches are proposed to simulate the avalanches numerically. The first considers the transformation of the avalanche domain into a simple shape domain that does not change in time. The second is based on the level set method, which is suitable for free boundary problems. Finally, the characteristics of the variation of the interface between avalanche and snowcover under a similarity hypothesis is put forward. The model is validated through the comparison with some experimental data.
Cold Regions Science and Technology, 2013
(AAM) is copyrighted and published by Elsevier. It is posted here by agreement between Elsevier a... more (AAM) is copyrighted and published by Elsevier. It is posted here by agreement between Elsevier and the University of Turin. Changes resulting from the publishing process-such as editing, corrections, structural formatting, and other quality control mechanisms-may not be reflected in this version of the text. The definitive version of the text was subsequently published in COLD REGIONS SCIENCE AND TECHNOLOGY, 86, 2013, 10.1016/j.coldregions.2012.10.014. You may download, copy and otherwise use the AAM for non-commercial purposes provided that your license is limited by the following restrictions: (1) You may use this AAM for non-commercial purposes only under the terms of the CC-BY-NC-ND license. (2) The integrity of the work and identification of the author, copyright owner, and publisher must be preserved in any copy.
Applied Mechanics and Materials, 2011
The paper aims to analyse the e ects of topography and building position on themagnitude of press... more The paper aims to analyse the e ects of topography and building position on themagnitude of pressure exerted by snow avalanches against buildings, through a structural backanalysis and numerical uid-dynamics. Studying a real snow avalanche impact occurred in2008 which destroyed a village in Valsavarenche (Aosta Valley - IT), the attention is focused onthe avalanche ow deviation caused by the destructive interaction with a rst building, whichprotected part of a second building beyond it. By means of photographical and in situ survey,a detailed description of avalanche geometrical, dynamical and physical properties is outlined.A structural investigation, based both on debris arrangement and on measurements on theundamaged parts of buildings is also carried out.Thus, a back analysis is carried out in order to de ne collapse dynamics and to estimate theupper and the lower bound of impact pressure. Afterwards, numerical uid-dynamical analysesare performed to simulate di erent impact scen...
Avalanche risk management assumes an in-depth knowledge of the nivometeorological situation to wh... more Avalanche risk management assumes an in-depth knowledge of the nivometeorological situation to which tools for the definition of avalanche potential release can be associated. The application of the PRA tool, developed by the SLF, on 600 real cases in Aosta Valley showed the important role played by the wind direction in determining scenarios of avalanche detachment. On those basis a rapid method has been developed, using the 10m wind intensity and direction data provided by the Cosmoi2 predictive model. The wind direction input was calculated by averaging vectorially the wind directions over the 24h, weighted with the cube of the intensity. In order to validate this procedure, the data elaborated with our procedure were compared with 1) the data of 52 automatic stations and 2) the observations contained in the Models 1 A.I.NE.VA. Scenarios of possible snow eroded / loaded areas are realized according to the wind direction at both valley and single-basin scales. Daily, after 40 minu...