scholarly journals Modeling debris-flow runout patterns on two alpine fans with different dynamic simulation models

2015 ◽  
Vol 3 (2) ◽  
pp. 1397-1425 ◽  
Author(s):  
K. Schraml ◽  
B. Thomschitz ◽  
B. W. McArdell ◽  
C. Graf ◽  
R. Kaitna
Keyword(s):  
Numerical Simulation ◽  
Debris Flow ◽  
Initial Conditions ◽  
Mass Movement ◽  
Simulation Models ◽  
Realistic Model ◽  
Three Dimensions ◽  
Sensitivity Analyses ◽  
Model Parameters ◽  
Alpine Regions

Abstract. Predicting potential deposition areas of future debris-flow events is important for engineering hazard assessment in alpine regions. For this, numerical simulation models are commonly used tools. However, knowledge of appropriate model parameters is essential but often not available. In this study we use two numerical simulation models, RAMMS-DF (Rapid Mass Movement System – Debris Flow) and DAN3D (Dynamic Analysis of Landslides in Three Dimensions), to back-calculate two well-documented debris-flow events in Austria and to compare the range and sensitivity of input parameters for the Voellmy flow model. All simulations are based on the same digital elevation model with a 1 m resolution and similar initial conditions. Our results show that both simulation tools are capable of matching observed deposition patterns. The best fit parameter set of μ [–] and ξ [m s−2] range between 0.07–0.11 and 200–300 m s−2, respectively, for RAMMS-DF, and 0.07–0.08 and 300–400 m s−2, respectively, for DAN3D. Sensitivity analyses show a higher sensitivity of model parameters for the DAN3D model than for the RAMMS-DF model. This study shall contribute to the evaluation of realistic model parameters for simulation of debris-flows in steep mountain catchments and highlights the sensitivity of the models.

scholarly journals Modeling debris-flow runout patterns on two alpine fans with different dynamic simulation models

2015 ◽  
Vol 15 (7) ◽  
pp. 1483-1492 ◽  
Author(s):  
K. Schraml ◽  
B. Thomschitz ◽  
B. W. McArdell ◽  
C. Graf ◽  
R. Kaitna
Keyword(s):  
Numerical Simulation ◽  
Debris Flow ◽  
Mass Movement ◽  
Simulation Models ◽  
Realistic Model ◽  
Three Dimensions ◽  
Model Parameters ◽  
Alpine Regions ◽  
Digital Elevation ◽  
Higher Sensitivity

Abstract. Predicting potential deposition areas of future debris-flow events is important for engineering hazard assessment in alpine regions. To this end, numerical simulation models are commonly used tools. However, knowledge of appropriate model parameters is essential but often not available. In this study we use two numerical simulation models, RAMMS–DF (rapid mass movement system–debris-flow) and DAN3D (dynamic analysis of landslides in three dimensions), to back-calculate two well-documented debris-flow events in Austria and to compare the range and sensitivity of input parameters for the Voellmy flow model. All simulations are based on the same digital elevation models and similar boundary conditions. Our results show that observed deposition patterns are best matched with a parameter set of μ [–] and ξ [m s-2], ranging between 0.07 to 0.11 and 200 to 300 m s-2, respectively, for RAMMS–DF, and between 0.07 to 0.08 and 300 to 400 m s-2, respectively, for DAN3D. Sensitivity analysis shows a higher sensitivity of model parameters for the DAN3D model than for the RAMMS–DF model. This contributes to the evaluation of realistic model parameters for simulation of debris-flows in steep mountain catchments and highlights the sensitivity of the models.

Numerical Simulation of Thin-Film Photovoltaic Solar Cells

2011 ◽  
Author(s):  
Khairy Sayed ◽  
Mazen Abdel-Salam ◽  
Mahmoud Ahmed ◽  
Adel A. Ahmed
Keyword(s):  
Numerical Simulation ◽  
Solar Cells ◽  
Simulation Models ◽  
Three Dimensions ◽  
Photovoltaic Module ◽  
Test Bed ◽  
Governing Equations ◽  
Simulation Code ◽  
Current Voltage ◽  
Photovoltaic Solar Cells

The objective of this work is to develop a detailed numerical simulation of solar photovoltaic cells in one, two, and three-dimensions. Such kind of numerical simulation can be used as a flexible research tool for the design and analysis of solar cells. The developed in-house simulation code has the advantage of conducting modifications of the suggested configurations to include effects not covered by the commercial simulation models. In addition, this tool is to serve as a test-bed simulator for the development of solar cells modeling and to design new material models. The photovoltaic solar cells governing equations are Poisson’s equation, the hole and electron continuity equations. Poisson equation is generally used to get the voltages across the device. However, in the present work, it is used to obtain the value of the electrical charge. The governing equations along with the appropriate boundary conditions are solved numerically using a finite difference based method. The resulting system of coupled nonlinear equations is then solved using Newton method for nonlinear systems. The predicted results include illuminated current-voltage characteristic, and dark current-voltage characteristics of photovoltaic module. Comparisons between predicted results and corresponding measured values by manufacturer are conducted in order to validate the numerical simulation. A good agreement between predicted and measured results was prevailed.

Simplified simulation of rock avalanches and subsequent debris flows with a single thin-layer model. Application to the Prêcheur river (Martinique, Lesser Antilles)

2021 ◽  
Author(s):  
Marc Peruzzetto ◽  
Clara Levy ◽  
Yannick Thiery ◽  
Gilles Grandjean ◽  
Anne Mangeney ◽  
...  
Keyword(s):  
Debris Flow ◽  
Thin Layer ◽  
Debris Flows ◽  
Initial Conditions ◽  
Rock Avalanche ◽  
Numerical Code ◽  
Lesser Antilles ◽  
Rheological Parameters ◽  
Model Parameters ◽  
High Discharge

<p>This work focuses on the use of thin-layer models for simulating fast gravitational flows for hazard assessment. Such simulations are sometimes difficult to carry out because of the uncertainty on initial conditions and on simulation parameters. In this study, we aggregate various field data to constrain realistic initial conditions and to calibrate the model parameters. By using the SHALTOP numerical code, we choose a simple and empirical rheology to model the flow (no more than two parameters), but we model more finely the geometrical interactions between the flow and the topography. We can thus model both a rock avalanche, and the subsequent remobilization of the deposits as a high discharge debris flow.</p><p>Using the Prêcheur river catchment (Martinique, Lesser Antilles) as a case study, we focus on extreme events with a high potential to impact populations and infrastructures. We use geological and geomorphological data, topographic surveys, seismic recordings and granulometric analysis to define realistic simulation scenarios and determine the main characteristics of documented events. The latter are then reproduced to calibrate rheological parameters. With a single rheological parameter and the Coulomb rheology, we thus model the emplacement and main dynamic characteristics of a recent rock avalanche, as well as the travel duration and flooded area of a documented high discharge debris flow. Then, in a forward prediction simulation, we model a possible 1.9x10<sup>6 </sup>m<sup>3</sup> rock avalanche, and the instantaneous remobilization of the resulting deposits as a high-discharge debris flow. We show that successive collapses allow to better reproduce the dynamics of the rock avalanche, but do not change the geometry of the final deposits, and thus do not influence the initial conditions of the subsequent debris flow simulation. A progressive remobilization of the materials slows down the debris flow and limits overflow, in comparison to instantaneous release. However, we show that high discharge debris flows, such as the one considered for model calibration, are better reproduced with an instantaneous initiation. The range of travel times measured for other significant debris flows in the Pr\^echeur river is consistent with our simulation results, with various rheological parameters and the Coulomb or Voellmy rheology.</p>

Simulation of Tethered Underwater Kites Moving in Three Dimensions for Power Generation

2017 ◽  
Author(s):  
Amirmahdi Ghasemi ◽  
David J. Olinger ◽  
Gretar Tryggvason
Keyword(s):  
Numerical Simulation ◽  
Power Generation ◽  
Stokes Equations ◽  
Simulation Models ◽  
Three Dimensions ◽  
Ocean Current ◽  
Design Parameters ◽  
Immersed Boundary ◽  
Computational Domain ◽  
Flow Equations

In this paper, a numerical simulation of tether undersea kites (TUSK) used for power generation is undertaken. The effect of varying key design parameters in these systems is studied. TUSK systems consist of a rigid-winged kite, or glider, moving in an ocean current. One proposed TUSK concept uses a tethered kite which is connected by a flexible tether to a support structure with a generator on a surface buoy. The numerical simulation models the flow field in a three-dimensional domain near the rigid undersea kite wing by solving the full Navier-Stokes equations. A moving computational domain method is used to reduce the computational run times. A second-order corrector-predictor method, along with Open Multi-Processing (OpenMP), is employed to solve the flow equations. In order to track the rigid kite, which is a rectangular planform wing with a NACA 0021 airfoil, an immersed boundary method is used. The tension force in the elastic tether is modeled by a simple Hooke’s law, and the effect of tether damping is added. PID control methods are used to adjust the kite pitch, roll and yaw angles during power (tether reel-out) and retraction (reel-in) phases to obtain the desired kite trajectories. During the reel-out phase the kite moves in successive cross-current motions in a figure-8 pattern, the tether length increases and power is generated. During reel-in the kite motion is along the tether, and kite hydrodynamic forces are reduced so that net positive power is produced. The effects of different key design parameters in TUSK systems, such as the ratio of tether to current velocity, and tether retraction velocity, are then further studied. System power output, kite trajectories, and vorticity flow fields for the kite are also determined.

scholarly journals Numerical Simulation on the Dynamic Characteristics of a Tremendous Debris Flow in Sichuan, China

Processes ◽  
2018 ◽  
Vol 6 (8) ◽  
pp. 109 ◽  
Author(s):  
Yulong Chen ◽  
Zhenfeng Qiu ◽  
Bo Li ◽  
Zongji Yang
Keyword(s):  
Numerical Simulation ◽  
Debris Flow ◽  
Construction Projects ◽  
Initial Conditions ◽  
Geometry Model ◽  
Finite Element Software ◽  
Flow Geometry ◽  
Computational Fluid Dynamics Cfd ◽  
Volume Method ◽  
Velocity Pressure

The mega debris flow that occurred on 13 August 2010 in Zoumaling Valley in Mianzhu County, China has done great damage to the local inhabitants, as well as to the re-construction projects in the quake-hit areas. Moreover, it is of high possibility that a secondary disaster would reappear and result in worse consequences. In order to maximize risk reduction of this problem, the local government planned to construct seven debris-resisting barriers across each ditch for mitigation of debris flow hazards in the future. In this paper, the numerical simulation fields of flow velocity, pressure, and mud depth of the Zoumaling debris flow had been computed by using finite volume method software based on computational fluid dynamics (CFD). The Bingham fluid was chosen as the constitutive model of this debris flow. The debris flow geometry model was a 3D model. The initial conditions, boundary conditions, control equations, and parameters were determined and adjusted by the actual conditions and analyses. The flow field data obtained from numerical simulations were substituted into the finite element software ANSYS. Then the calculations of fluid-solid coupling action between the flow and dam had been done. All these results of simulations and analyses could be the guide and suggestion for the design and construction of prevention engineering of Zoumaling debris flow.

scholarly journals Debris Flow Modelling Using RAMMS Model in the Alpine Environment With Focus on the Model Parameters and Main Characteristics

2021 ◽  
Vol 8 ◽  
Author(s):  
Matjaž Mikoš ◽  
Nejc Bezak
Keyword(s):  
Debris Flow ◽  
Debris Flows ◽  
Mass Movement ◽  
Friction Model ◽  
Economic Damage ◽  
Model Parameters ◽  
Comprehensive Overview ◽  
Alpine Environment ◽  
Flow Modelling ◽  
Parameter Ranges

Debris flows are among the natural hazards that can occur in mountainous areas and endanger people’s lives and cause large economic damage. Debris flow modelling is needed in multiple applications such as design of protection measures or preparation of debris flow risk maps. Many models are available that can be used for debris flow modelling. The Rapid Mass Movement Simulation (RAMMS) model with its debris flow module, (i.e. RAMMS-DF) is one of the most commonly used ones. This review provides a comprehensive overview of past debris flow modelling applications in an alpine environment with their main characteristics, including study location, debris flow magnitude, simulation resolution, and Voellmy-fluid friction model parameter ranges, (i.e. μ and ξ). A short overview of each study is provided. Based on the review conducted, it is clear that RAMMS parameter ranges are relatively wide. Furthermore, model calibration using debris-flow post-event survey field data is the essential step that should be done before applying the model. However, an overview of the parameters can help to limit the parameter ranges. Particularly when considering the similarity between relevant case studies conducted in similar environments. This is especially relevant should the model be applied for estimating debris-flow hazard for potential future events. This model has been used mostly in Europe, (i.e. Alpine region) for modelling small and extremely large debris flows.

Development of Numerical Simulation Method for Relocation Behavior of Molten Debris in Nuclear Reactors: 1 — Preliminary Analysis of Relocation of Molten Debris to Lower Plenum

2013 ◽  
Author(s):  
Susumu Yamashita ◽  
Hiroyuki Yoshida ◽  
Kazuyuki Takase
Keyword(s):  
Numerical Simulation ◽  
Solid Phase ◽  
Initial Conditions ◽  
Three Dimensional ◽  
Simulation Models ◽  
Simulation Method ◽  
Melting Behavior ◽  
Hydraulic Simulation ◽  
Numerical Simulation Method ◽  
Two Phases

We developed the numerical simulation method for predicting the melting core behavior including solidification and relocation based on the three-dimensional multi-phase thermal-hydraulic simulation models. In this code, each of gas, liquid and solid phase are treated individually, and interface between two phases are simulated directly. In this paper, the developed code was applied to numerical simulations of the melting behavior of the simulated fuel assemblies and reactor structures. In the simulation, complicated structures in the BWR lower plenum was simply modeled. A decay heat in molten or solidified debris was also considered. Moreover, several different initial conditions were used to check performance of this code and to evaluate adequacy of the present numerical method. From the present numerical results, it was confirmed that relocation of molten debris in the BWR lower plenum can be simulated by the currently developed code including effects of melting and solidification of debris.

The role of the phase shift of fine particles on debris flow behavior: an numerical simulation for a debris flow in Illgraben, Switzerland

2021 ◽  
Vol 58 (1) ◽  
pp. 23-34
Author(s):  
Taro Uchida ◽  
Yuki Nishiguchi ◽  
Brian W. McArdell ◽  
Yoshifumi Satofuka
Keyword(s):  
Numerical Simulation ◽  
Phase Shift ◽  
Debris Flow ◽  
Simulation Model ◽  
Debris Flows ◽  
Flow Behavior ◽  
Flow Characteristics ◽  
Simulation Models ◽  
Fine Sediment ◽  
Physically Based

Physically based numerical simulation models have been developed to predict hazard area relating to debris flows. Since fine sediments are expected to behave as a part of the fluid rather than solid phase in stony debris flows, several models have recently included this process of the phase shift from solid to fluid in the context of fine sediment. However, models have not been fully tested regarding the ability to reproduce a variety of debris flow characteristics. We therefore tested (i) applicability of a numerical simulation model for describing debris flow characteristics and (ii) the effect of phase shift of fine sediment on debris flow behaviors. Herein we applied a numerical simulation model to a well-documented dataset from the Illgraben debris flow observation station in Switzerland. Based on the stony debris flow concept, we physically modeled effects of the phase shift of sediment on transport capacity and flow resistance. We successfully reproduced the observed bulk density, erosion and deposition patterns, front velocity, and erosion rate, although we had to tune the ratio of fine sediment that behaves as a fluid. Considering the effects of the phase shift of sediments, we conclude that physically based numerical simulation models can describe a variety of debris flow behaviors.

Evoluzione della copertura vegetale in aree alpestri del Canton Ticino nel periodo 1971–2001 | Evolution of Vegetation Cover in the Alpine Regions of Canton Tessin: 1971–2001

2004 ◽  
Vol 155 (7) ◽  
pp. 284-289 ◽  
Author(s):  
Pietro Stanga ◽  
Niklaus Zbinden
Keyword(s):  
Initial Conditions ◽  
Ground Cover ◽  
Climatic Conditions ◽  
Human Pressure ◽  
Aerial Photos ◽  
Alpine Regions ◽  
Subsequent Decrease ◽  
Site Fertility ◽  
Strong Expansion ◽  
Evolution Of Vegetation

The retrospective study based on aerial photos (1971–2001) of the Canton Tessin made it possible to measure and analyze the evolution of the vegetation of eleven Alpine zones. The analysis shows a strong expansion of the arborescent vegetation and, at the same time, a decrease in other forms of ground cover (bush, shrub, meadow and unproductive spaces). Analysis of the data gives rise to the conjecture that the strong evolutionary dynamism evidenced by the areas under investigation is a result of the vast clearings carried out in past centuries to create pastures. Following the subsequent decrease in human pressure, nature today is attempting to rebalance the level of the biomass. These processes manifest themselves in different ways and with various intensity, depending on the interaction of numerous factors (e.g. climatic conditions, site fertility, initial conditions, evolution of anthropological pressure, etc.).

scholarly journals Optimal Investment and Proportional Reinsurance in a Regime-Switching Market Model under Forward Preferences

Mathematics ◽  
2021 ◽  
Vol 9 (14) ◽  
pp. 1610
Author(s):  
Katia Colaneri ◽  
Alessandra Cretarola ◽  
Benedetta Salterini
Keyword(s):  
Stock Prices ◽  
Regime Switching ◽  
Common Factor ◽  
Optimal Investment ◽  
Investment Strategy ◽  
Market Model ◽  
Sensitivity Analyses ◽  
Model Parameters ◽  
Insurance Company ◽  
Optimal Investment Strategy

In this paper, we study the optimal investment and reinsurance problem of an insurance company whose investment preferences are described via a forward dynamic exponential utility in a regime-switching market model. Financial and actuarial frameworks are dependent since stock prices and insurance claims vary according to a common factor given by a continuous time finite state Markov chain. We construct the value function and we prove that it is a forward dynamic utility. Then, we characterize the optimal investment strategy and the optimal proportional level of reinsurance. We also perform numerical experiments and provide sensitivity analyses with respect to some model parameters.

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