scholarly journals Three-dimensional and real-scale modeling of flow regimes in dense snow avalanches

Landslides ◽  
2021 ◽  
Author(s):  
Xingyue Li ◽  
Betty Sovilla ◽  
Chenfanfu Jiang ◽  
Johan Gaume
Keyword(s):  
Three Dimensional ◽  
Economic Loss ◽  
Density Variation ◽  
Material Point ◽  
Snow Avalanche ◽  
Snow Avalanches ◽  
Computationally Efficient ◽  
Mountainous Regions ◽  
Depth Direction ◽  
Wide Range

AbstractSnow avalanches cause fatalities and economic loss worldwide and are one of the most dangerous gravitational hazards in mountainous regions. Various flow behaviors have been reported in snow avalanches, making them challenging to be thoroughly understood and mitigated. Existing popular numerical approaches for modeling snow avalanches predominantly adopt depth-averaged models, which are computationally efficient but fail to capture important features along the flow depth direction such as densification and granulation. This study applies a three-dimensional (3D) material point method (MPM) to explore snow avalanches in different regimes on a complex real terrain. Flow features of the snow avalanches from release to deposition are comprehensively characterized for identification of the different regimes. In particular, brittle and ductile fractures are identified in the different modeled avalanches shortly after their release. During the flow, the analysis of local snow density variation reveals that snow granulation requires an appropriate combination of snow fracture and compaction. In contrast, cohesionless granular flows and plug flows are mainly governed by expansion and compaction hardening, respectively. Distinct textures of avalanche deposits are characterized, including a smooth surface, rough surfaces with snow granules, as well as a surface showing compacting shear planes often reported in wet snow avalanche deposits. Finally, the MPM modeling is verified with a real snow avalanche that occurred at Vallée de la Sionne, Switzerland. The MPM framework has been proven as a promising numerical tool for exploring complex behavior of a wide range of snow avalanches in different regimes to better understand avalanche dynamics. In the future, this framework can be extended to study other types of gravitational mass movements such as rock/glacier avalanches and debris flows with implementation of modified constitutive laws.

scholarly journals Calculation of 3D Coordinates of a Point on the Basis of a Stereoscopic System

2018 ◽  
Vol 8 (1) ◽  
pp. 109-117
Author(s):  
R.R. Mussabayev ◽  
M.N. Kalimoldayev ◽  
Ye.N. Amirgaliyev ◽  
A.T. Tairova ◽  
T.R. Mussabayev
Keyword(s):  
Optical System ◽  
Three Dimensional ◽  
Material Point ◽  
Experimental Investigations ◽  
Unknown Parameters ◽  
Wide Range ◽  
Stereoscopic System ◽  
3D Scene ◽  
The Right ◽  
The Given

Abstract The solution of three-dimensional (3D) coordinate calculation task for a material point is considered. Two flat images (a stereopair) which correspond to the left and to the right viewpoints of a 3D scene are used for this purpose. The stereopair is obtained using two cameras with parallel optical axes. The analytical formulas for calculating 3D coordinates of a material point in the scene were obtained on the basis of analysis of the stereoscopic system optical and geometrical schemes. The detailed presentation of the algorithmic and hardware realization of the given method was discussed with the the practical. The practical module was recommended for the determination of the optical system unknown parameters. The series of experimental investigations were conducted for verification of theoretical results. During these experiments the minor inaccuracies were occurred by space distortions in the optical system and by it discrecity. While using the high quality stereoscopic system, the existing calculation inaccuracy enables to apply the given method for the wide range of practical tasks.

scholarly journals Use of a Two-Dimensional Simulation Model in the Thermal Analysis of a Multi-Board Electronic Module

1994 ◽  
Vol 116 (2) ◽  
pp. 126-133 ◽  
Author(s):  
C. Beckermann ◽  
T. F. Smith ◽  
B. Pospichal
Keyword(s):  
Heat Transfer ◽  
Simulation Model ◽  
Three Dimensional ◽  
Two Dimensional ◽  
Circuit Boards ◽  
Depth Direction ◽  
Wide Range ◽  
Local Board ◽  
Dimensional Simulation ◽  
Effective Component

A study is reported of heat transfer and air flow in an electronic module consisting of an array of narrowly spaced vertical circuit boards with highly-protruding components contained in a naturally vented chassis. A two-dimensional simulation model is developed that accounts for heat transfer by conduction, convection, and radiation, and sensitivity studies are performed. Experiments are conducted using a specially constructed test module. Comparisons with the experiments reveal the need to calibrate the model by selecting an effective component height that represents the drag properties of the actual three-dimensional component geometry. The need to account in the model for heat losses in the depth direction is also discussed. The importance of accurate thermophysical properties and of multi-dimensional radiation is shown. Good agreement with measured velocities and local board temperatures is obtained over a wide range of power levels, and it is concluded that the calibrated model is capable of representing the thermal behavior of the present module.

Three-dimensional material point method modeling of runout behavior of the Hongshiyan landslide

2019 ◽  
Vol 56 (9) ◽  
pp. 1318-1337 ◽  
Author(s):  
Xiaorong Xu ◽  
Feng Jin ◽  
Qicheng Sun ◽  
Kenichi Soga ◽  
Gordon G.D. Zhou
Keyword(s):  
Progressive Failure ◽  
Three Dimensional ◽  
Material Point Method ◽  
Numerical Approach ◽  
Flow Speed ◽  
Material Point ◽  
Point Method ◽  
Field Scale ◽  
Rate Dependent ◽  
Depth Direction

This study presents a field-scale simulation of the Hongshiyan landslide in China. It uses an advanced numerical approach (material point method (MPM)) and a constitutive model (the Drucker–Prager model + μ(I) rheological relation) for the three-dimensional (3D) simulation. The performance of the developed MPM model is validated with laboratory-scale experimental data on granular collapse before being applied to field-scale analyses. ArcGIS data are used to create a 3D MPM model of the soil body with complicated geometry. Although the developed model can describe the multiple phases of granular flow, it focuses on the runout behavior of the landslide in this work. The landslide is assumed to have occurred suddenly due to an earthquake, and global sudden failure rather than progressive failure is modeled. The MPM simulation results match reasonably well with the measured post-earthquake topography (e.g., deposit height of about 120 m and stretch length of about 900 m in the river) and landslide duration of about 1 min. The velocity of the sliding mass increases rapidly during flow, especially in the first 20 s. The velocity profiles along the depth direction at different locations of the sliding body exhibit an exponential distribution similar to that of a Bagnold-type profile, indicating that the sliding body is fully mobilized. The rate-dependent dissipation parameter β used in the model significantly influences the runout behavior (e.g., flow speed, velocity distribution, and deposit shape).

An Efficient CFD Model for Air/Particle Saltating Flows

2002 ◽  
Author(s):  
S. Ji ◽  
A. G. Gerber ◽  
A. C. M. Sousa
Keyword(s):  
Particle Concentration ◽  
Particle Surface ◽  
Three Dimensional ◽  
Phase System ◽  
Cfd Model ◽  
Computationally Efficient ◽  
Dynamics Model ◽  
Three Dimensional Flow ◽  
Two Phase ◽  
Wide Range

The study reports on the development of a computational-fluid-dynamics model is presented suitable for computationally efficient evaluation of particle transport along loose surfaces. These surfaces can be described within the context of an interaction with a two-phase air/particle mixture in a state of combined suspension and saltation. The results suggest an approach for approximating the two-phase system with coupling to a moving surface, along with the inclusion of impact and entrainment fluxes at the surface that is generally extendable to a wide range of particle/surface conditions. The model results are compared to available experimental data on particle concentration profiles along saltating surfaces, and applied to geometry involving complex three-dimensional flow to show the generality of the approach.

A Comprehensive Through-Flow Solver Method for Modern Turbomachinery Design

2015 ◽  
Author(s):  
Mark R. Anderson ◽  
Daryl L. Bonhaus
Keyword(s):  
High Speed ◽  
Three Dimensional ◽  
Optimization Techniques ◽  
Navier Stokes ◽  
Computationally Efficient ◽  
Dimensional Solution ◽  
Loss Model ◽  
Flow Solver ◽  
Through Flow ◽  
Wide Range

Through-flow solvers have historically played a very prominent role in the design and analysis of axial turbomachinery. While three-dimensional, Full Navier-Stokes (FNS) CFD is taking an increasing larger role, quasi-3D through-flow methods are still widely used. Automated optimization techniques that search over a wide design space, involving many possible variables, are particularly suitable for the computationally efficient through-flow solver. Pressure-based methods derived from CFD solution techniques have gradually replaced older streamline curvature methods, due to their ability to capture flow across a wide range of Mach numbers, particularly the transonic and supersonic regimes. The through-flow approach allows for the solution of the three-dimensional problem with the computational efficiency of a two-dimensional solution. Since the losses are explicitly calculated through empirically based models, the need for detailed grid resolution to capture tiny flow entities (such as wakes and boundary layers) is also greatly reduced. The combined savings can result in computational costs as much as two orders of magnitude lower than full 3D CFD methods. A state-of-the-art through-flow solver has several features that are crucial in the design process. One of these is the ability to run in both a design and an analysis mode. Also important, is the ability to generate solutions where critical components are solved using 3D FNS, while others are run using a through-flow method. Other desirable features in a through-flow solver are: an advanced equation of state, injection and extraction ability, the handling of arbitrary (non-axial) shapes, and a link to a capable geometry generation engine. Through-flow solvers represent a unique mix of higher order numerical methods (increasingly CFD-based) coupled with empirically derived models (generally meanline based). The combination of these two methods in one solver creates a particularly challenging programming problem. This paper details the techniques required to effectively generate through-flow solutions. Special attention is given to an improved off-design loss model for compressors, as well as a transonic loss model needed for high-speed compressor and turbine flows. Validation with recognized test data along with corresponding 3D FNS CFD results are presented.

Modeling of snow avalanche dynamics using open source software OpenFOAM

2021 ◽  
Author(s):  
Daria Romanova ◽  
Margarita Egiit
Keyword(s):  
Three Dimensional ◽  
Snow Avalanche ◽  
Machine Learning Techniques ◽  
Turbulent Regime ◽  
Snow Avalanches ◽  
Advantages And Disadvantages ◽  
Three Dimensional Modeling ◽  
The Neural Network ◽  
Learning Techniques ◽  
Protective Structures

<p>The work is devoted to the comparison of different approaches for modeling the dynamics of dense and powder snow avalanches. Various 3D and 2D approaches are considered. The accuracy of determining the avalanche run-out zone, the interaction of the flow with obstacles, the front speed, and various distributed parameters are evaluated. As objects for comparison, an experiment on the interaction of a slushflow with a combination of protective structures and a powder snow avalanche in the Khibiny mountains are modeled.</p><p> </p><p>Taking into account the advantages and disadvantages of various approaches based on basic solutions available in the OpenFOAM package, a specialized software avalancheFoam is being developed for three-dimensional modeling of the dynamics of snow avalanches, taking into account the complex turbulent regime and multiphase structure of the flow. Machine learning techniques are used to refine turbulent stresses. The neural network is trained on a dataset obtained from high-precision supercomputer simulation of the flow, and sets the form of additional refinement members of the mathematical model of less computational complexity. Various avalanche sites in the Khibiny mountains are modeled to validate the developed software.</p>

scholarly journals Snow avalanche friction relation based on extended kinetic theory

2016 ◽  
Author(s):  
Matthias Rauter ◽  
Jan-Thomas Fischer ◽  
Wolfgang Fellin ◽  
Andreas Kofler
Keyword(s):  
Kinetic Theory ◽  
Three Dimensional ◽  
Field Tests ◽  
Friction Model ◽  
Snow Avalanche ◽  
Snow Avalanches ◽  
Rheological Models ◽  
Physically Based Model ◽  
Physically Based

Abstract. Rheological models for granular materials play an important role in the numerical simulation of dry dense snow avalanches. This article describes the application of a physically based model from the field of kinetic theory to snow avalanche simulations. Those are usually based on depth-averaged two-dimensional models. Therefore a method to adapt the three-dimensional rheological model is presented. In a further step simulation results are compared to velocity and runout observations of avalanches, recorded from different field tests. As reference we utilize a classic phenomenological friction model, which is commonly applied for hazard estimation. The quantitative comparison is based on the combination of normalized residuals of different observation variables in order to take into account the quality of the simulations in various regards. It is demonstrated that the kinetic theory provides a physically based explanation for the structure of phenomenological friction relations and contributes improvements, in particular when different events and various observation variables are investigated.

scholarly journals Perspectives on Snow Avalanche Dynamics Research

Geosciences ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 57
Author(s):  
Kouichi Nishimura ◽  
Fabrizio Barpi ◽  
Dieter Issler
Keyword(s):  
Experimental Studies ◽  
Snow Avalanche ◽  
Particle Interactions ◽  
Snow Avalanches ◽  
Special Issue ◽  
Erosion And Deposition ◽  
Field Surveys ◽  
Wide Range ◽  
Avalanche Dynamics ◽  
Avalanche Flow

As an introduction for non-specialists to the Special Issue on snow avalanche dynamics, this paper first outlines how understanding the dynamics of snow avalanches can contribute to reducing risk for settlements and infrastructure. The main knowledge gaps in this field of research concern (i) the properties of the flow regimes and the transitions between them, and (ii) the dynamics of mass change due to erosion and deposition. These two aspects are intertwined and determine not only the reach of an avalanche, but also its velocity, course and impact pressure. Experimental studies described in this Special Issue comprise a wide range of scales from small rotating drums to real snow avalanches. In addition, several papers describe post-event field surveys of specific avalanches and analyze them using different methods and techniques, demonstrating how valuable qualitative insight can be gained in this way. The theoretical developments range from exploratory studies of fluid–particle interactions to a comprehensive review of half a century of avalanche flow modeling in Russia.

scholarly journals Detrainment and braking of snow avalanches interacting with forests

2021 ◽  
Author(s):  
Louis Védrine ◽  
Xingyue Li ◽  
Johan Gaume
Keyword(s):  
Large Strain ◽  
Soil Mechanics ◽  
Three Dimensional ◽  
Field Measurements ◽  
Material Point ◽  
Snow Avalanches ◽  
Reference Case ◽  
Forest Density ◽  
Snow Properties ◽  
Wet Snow

Abstract. Mountain forests provide natural protection against avalanches. They can both prevent avalanche formation in release zones and reduce avalanche mobility in runout areas. Although the braking effect of forests has been previously explored through global statistical analyses on documented avalanches, little is known about the mechanism of snow detrainment in forests for small and medium avalanches. In this study, we investigate the detrainment and braking of snow avalanches in forested terrain, by performing three-dimensional simulations using the Material Point Method (MPM) and a large strain elastoplastic snow constitutive model based on Critical State Soil Mechanics. First, the snow internal friction is evaluated using existing field measurements based on the detrainment mass, showing the feasibility of the numerical framework and offering a reference case for further exploration of different snow types. Then, we systematically investigate the influence of snow properties and forest parameters on avalanche characteristics. Our results suggest that, for both dry and wet avalanches, the detrainment mass decreases with the square of the avalanche front velocity before it reaches a plateau value. Furthermore, the detrainment mass significantly depends on snow properties. It can be as much as ten times larger for wet snow compared to dry snow. By examining the effect of forest configurations, it is found that forest density and tree diameter have cubic and square relations with the detrainment mass, respectively. The outcomes of this study may contribute to the development of improved formulations of avalanche–forest interaction models in popular operational simulation tools and thus improve hazard assessment for alpine geophysical mass flows in forested terrain.

scholarly journals Methods of snow avalanche nourishment assessment (on the example of three Tian Shan glaciers)

2019 ◽  
Vol 59 (4) ◽  
pp. 460-474
Author(s):  
A. S. Turchaninova ◽  
A. V. Lazarev ◽  
E. S. Marchenko ◽  
Yu. G. Seliverstov ◽  
S. A. Sokratov ◽  
...  
Keyword(s):  
Data Analysis ◽  
Snow Accumulation ◽  
Tien Shan ◽  
Data Availability ◽  
Snow Avalanche ◽  
Weather Data ◽  
Snow Avalanches ◽  
Mountain Glaciers ◽  
Mountainous Regions ◽  
Numerical Assessment

The contribution of snow avalanches to the seasonal snow accumulation on a glacier is among the least studied components of the glacier’s mass balance. The methods for the numerical assessment of avalanche accumulation are still under development, which is related to poor avalanche data availability and difficulties in obtaining such data on most of mountain glaciers. We propose a possible methodology for the numerical assessment of snow avalanche contribution to snow accumulation at mountain glaciers based on DEM and weather data analysis using GIS and numerical modeling of snow avalanches. The developed methodology consists of the following steps: terrain analysis; weather data analysis; snow avalanche volume assessment during an analyzed balance year; numerical simulation of snow avalanches using RAMMS; evaluation of snow avalanches contribution into a glacier accumulation. The proposed methodology was tested on three glaciers located in the Inner Tien Shan: Batysh Sook, № 354 and Karabatkak during the 2015/16 balance year. To evaluate snow avalanche contribution to the seasonal accumulation, we reconstructed avalanche release zones that were most probably active during the 2015/16 balance year and corresponding snow fracture height in each of these zones. The numerical simulations of most probable released snow avalanches during the winter period 2015/16 using avalanche dynamics software RAMMS were performed and compared with the field observations and UAV orthophoto image from July 2016. The outlines of avalanches deposits were realistically reproduced by RAMMS according to the results of field observation. The estimated share of snow avalanche contribution to the accumulation on the research glaciers during the 2015/16 balance year turned out to be: Batysh Sook – 7,4±2,5%; № 354 – 2,2±0,7%; Karabatkak – 10,8±3,6% of the total accumulation. The next step would be to test the proposed methodology based on the data and regional dependences from the Inner Tien Shan in other mountainous regions. This methodology is applicable in the regions where DEMs, regular meteorological observations as well as data on the regional avalanche formation factors are available.

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