scholarly journals Numerical investigation and application of 3D multi-phase non-Newtonian rheology model for debris flow

2021 ◽  
Author(s):  
Rui Li ◽  
Yuliang Teng
Keyword(s):  
Experimental Data ◽  
Debris Flow ◽  
Flow Model ◽  
Good Accuracy ◽  
Flow Simulation ◽  
Field Investigation ◽  
Plane Case ◽  
Improved Model ◽  
Multi Phase ◽  
Rheology Model

Abstract A 3D multiphase debris flow model – DebrisInterMixingFoam was studied. An improvement to include the VOF field updating in the iteration of updating the flow field variables was proposed. The improved model was first validated by a debris flow deposition on slope plane case. Then the model was applied to two benchmark debris flow cases and a real debris flow event. In all cases, the model results were favorably compared with the experimental data or field investigation data. As there were only two key parameters to be calibrated in DebrisInterMixingFoam, it was easy to be used to model debris flow. The numerical results showed that this model can achieve good accuracy for debris flow simulation after calibrations of these two key parameters.

A Dilatant, Two-Phase Debris Flow Model for Hazard Mitigation

2021 ◽  
Author(s):  
Guillaume Meyrat
Keyword(s):  
Debris Flow ◽  
Practical Problem ◽  
Flow Model ◽  
Flow Behavior ◽  
Test Site ◽  
Recent Analysis ◽  
Water Type ◽  
Two Phase ◽  
Flow Measurements ◽  
Multi Phase

<p>Guillaume Meyrat, Brian McArdell, Ksenyia Ivanova, Perry Bartelt</p><p>WSL Institute for Forest, Snow and Landscape Research, 8903 Birmensdorf, Switzerland</p><p> </p><p><strong>Keywords</strong>: Debris flows, multi-phase models, dilatancy, shear stress, density distribution</p><p> </p><p>To implement an accurate numerical tool to simulate debris flow hazard is a longstanding goal of natural hazard research and engineering. In Switzerland the application of numerical debris flow models has, however, been hampered by many practical and theoretical difficulties. One practical problem is to define realistic initial conditions for hazard scenarios that involve both the rocky (granular solid) and muddy (fluid) material. Still another practical problem is to model debris flow growth by entrainment [1]. These problems are compounded by theoretical uncertainties regarding the rheological behavior of multi-phase flows. Recent analysis of debris flow measurements at the Swiss Illgraben test-site [2] (shear and normal stresses, debris flow height) show that the shear force, and therefore the entire debris flow behavior, is largely influenced by the debris flow composition, i.e. the amount of solid particle and muddy fluid at any specific location within the debris flow body (front, tail, etc.). The debris flow composition is, in turn, determined by the initial and entrainment conditions for a specific event. As a consequence, we have concluded that the very first step to construct a robust numerical model is to accurately predict the space and time evolution of the solid/fluid flow composition for any set of initial and boundary conditions. To this aim, we have developed a two-phase dilatant debris flow model [3, 4, 5] that is based on the idea that the dispersion of solid material in fluid phase can change over time. The model is thus able to predict different flow compositions (rocky fronts, watery tails), using shallow-water type mass, momentum and energy conservation equations. This helps to predict when the solid phase deposits, and when muddy fluid washes and channel outbreaks in the runout zone can occur. The parameters controlling the evolution of debris flow density and saturation have been derived by direct comparison to the full-scale measurements performed at the Illgraben test site.</p><p> </p><p><strong>References</strong></p><p><strong> </strong></p><p> </p>

scholarly journals Gradation and Rheological Characteristics of Glacial Debris Flow along the Kangding–Linzhi Section of Sichuan–Tibet Railway

2020 ◽  
Vol 2020 ◽  
pp. 1-12
Author(s):  
Shuliang Liu ◽  
Jichun Zhang ◽  
Xie Cheng ◽  
Wubin Wang ◽  
Hongtao Jiang
Keyword(s):  
Experimental Data ◽  
Debris Flow ◽  
Fine Particles ◽  
Disaster Risk ◽  
Field Investigation ◽  
Practical Significance ◽  
Rheological Characteristics ◽  
Coarse Particles ◽  
Viscous Debris Flow ◽  
Movement Rules

To date, most research on the characteristics of glacial debris flow along the Sichuan–Tibet railway has focused on numerical simulations and remote sensing, resulting in a lack of direct experimental data from debris flow samples. Therefore, in the present study, a field investigation was conducted along the Sichuan–Tibet railway, and 55 samples of glacial debris flow deposits were systematically analyzed to determine their grading and rheological properties. This is the first systematic experimental study on glacial debris flow deposits. The results showed that the proportion of coarse particles was high and the proportion of fine particles was low in the glacial debris flow along the Sichuan–Tibet railway. The average gravel and sand contents were 37.8% and 58%, respectively, and the average contents of silt and clay were 3.7% and 0.47%, respectively. The average fractal dimension was 2.1507, which is much greater than that of viscous debris flow. Under the same gravity and shear rate, the stress of typical glacial debris flow was significantly less than that of viscous debris flow, whereas the variability of the stress was more significant. These findings will contribute to revealing the movement rules and disaster risk of glacier debris flow along the Sichuan–Tibet railway and have considerable theoretical and practical significance for ensuring safety during both its construction and later operation.

Influence of Flexible Side-Chains on the Breathing Phase Transition of Pillared Layer MOFs: A Force Field Investigation

2020 ◽  
Author(s):  
Julian Keupp ◽  
Johannes P. Dürholt ◽  
Rochus Schmid
Keyword(s):  
First Principles ◽  
Good Accuracy ◽  
Field Investigation ◽  
Square Lattice ◽  
Side Chain ◽  
Second Step ◽  
Side Chains ◽  
Dynamics Simulations ◽  
Complex Phenomena ◽  
Closed Pore

The prototypical pillared layer MOFs, formed by a square lattice of paddle-<br>wheel units and connected by dinitrogen pillars, can undergo a breathing phase<br>transition by a “wine-rack” type motion of the square lattice. We studied this not<br>yet fully understood behavior using an accurate first principles parameterized force<br>field (MOF-FF) for larger nanocrystallites on the example of Zn 2 (bdc) 2 (dabco) [bdc:<br>benzenedicarboxylate, dabco: (1,4-diazabicyclo[2.2.2]octane)] and found clear indi-<br>cations for an interface between a closed and an open pore phase traveling through<br>the system during the phase transformation [Adv. Theory Simul. 2019, 2, 11]. In<br>conventional simulations in small supercells this mechanism is prevented by periodic<br>boundary conditions (PBC), enforcing a synchronous transformation of the entire<br>crystal. Here, we extend this investigation to pillared layer MOFs with flexible<br>side-chains, attached to the linker. Such functionalized (fu-)MOFs are experimen-<br>tally known to have different properties with the side-chains acting as fixed guest<br>molecules. First, in order to extend the parameterization for such flexible groups,<br>1a new parametrization strategy for MOF-FF had to be developed, using a multi-<br>structure force based fit method. The resulting parametrization for a library of<br>fu-MOFs is then validated with respect to a set of reference systems and shows very<br>good accuracy. In the second step, a series of fu-MOFs with increasing side-chain<br>length is studied with respect to the influence of the side-chains on the breathing<br>behavior. For small supercells in PBC a systematic trend of the closed pore volume<br>with the chain length is observed. However, for a nanocrystallite model a distinct<br>interface between a closed and an open pore phase is visible only for the short chain<br>length, whereas for longer chains the interface broadens and a nearly concerted trans-<br>formation is observed. Only by molecular dynamics simulations using accurate force<br>fields such complex phenomena can be studied on a molecular level.

scholarly journals A two-phase shallow debris flow model with energy balance

2015 ◽  
Vol 49 (1) ◽  
pp. 101-140 ◽  
Author(s):  
F. Bouchut ◽  
E.D. Fernández-Nieto ◽  
A. Mangeney ◽  
G. Narbona-Reina
Keyword(s):  
Energy Balance ◽  
Debris Flow ◽  
Flow Model ◽  
Two Phase

Larger-Eddy Simulation of Velocity Fluctuation in a Mixing T-Junction

2012 ◽  
Vol 152-154 ◽  
pp. 1313-1318
Author(s):  
Tao Lu ◽  
Su Mei Liu ◽  
Ping Wang ◽  
Wei Yyu Zhu
Keyword(s):  
Experimental Data ◽  
Velocity Fluctuation ◽  
Flow Model ◽  
Numerical Results ◽  
Mean Square ◽  
Main Duct ◽  
Velocity Fluctuations ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Les Model

Velocity fluctuations in a mixing T-junction were simulated in FLUENT using large-eddy simulation (LES) turbulent flow model with sub-grid scale (SGS) Smagorinsky–Lilly (SL) model. The normalized mean and root mean square velocities are used to describe the time-averaged velocities and the velocities fluctuation intensities. Comparison of the numerical results with experimental data shows that the LES model is valid for predicting the flow of mixing in a T-junction junction. The numerical results reveal the velocity distributions and fluctuations are basically symmetrical and the fluctuation at the upstream of the downstream of the main duct is stronger than that at the downstream of the downstream of the main duct.

A Numerical Investigation on the Volute/Diffuser Interaction due to the Axial Distortion at Impeller Exit

2000 ◽  
Author(s):  
Fahua Gu ◽  
Abraham Engeda ◽  
Mike Cave ◽  
Jean-Luc Di Liberti
Keyword(s):  
Experimental Data ◽  
Numerical Simulation ◽  
Numerical Investigation ◽  
Steady Flow ◽  
Centrifugal Compressor ◽  
Vortex Structure ◽  
Flow Model ◽  
Single Stage ◽  
Mass Flows

Abstract A numerical simulation is performed on a single stage centrifugal compressor using the commercially available CFD software, CFX-TASCflow. The steady flow is obtained by circumferentially averaging the exit fluxes of the impeller. Three runs are made at design condition and off-design conditions. The predicted performance is in agreement with experimental data. The flow details inside the stationary components are investigated, resulting in a flow model describing the volute/diffuser interaction at design and off-design conditions. The recirculation and twin vortex structure are found to explain the volute loss increase at lower and higher mass flows, respectively.

Accurate Multi-Phase Flow Simulation in Faulted Reservoirs Using Mimetic Finite Difference Methods on Polyhedral Cells

2021 ◽  
Author(s):  
Rencheng Dong ◽  
Faruk O. Alpak ◽  
Mary F. Wheeler
Keyword(s):  
Hybrid Method ◽  
Corner Point ◽  
Flow Simulation ◽  
Phase Flow ◽  
Reference Solution ◽  
Pressure Equation ◽  
Discretization Methods ◽  
Multi Phase Flow ◽  
Polyhedral Cells ◽  
Multi Phase

Abstract Faulted reservoirs are commonly modeled by corner-point grids. Since the two-point flux approximation (TPFA) method is not consistent on non-orthogonal grids, multi-phase flow simulation using TPFA on corner-point grids may have significant discretization errors if grids are not K-orthogonal. To improve the simulation accuracy, we developed a novel method where the faults are modeled by polyhedral cells, and mimetic finite difference (MFD) methods are used to solve flow equations. We use a cut-cell approach to build the mesh for faulted reservoirs. A regular orthogonal grid is first constructed,and then fault planes are added by dividing cells at fault planes. Most cells remain orthogonal while irregular non-orthogonal polyhedral cells can be formed with multiple cell divisions. We investigated three spatial discretization methods for solving the pressure equation on general polyhedral grids, including the TPFA, MFD and TPFA-MFD hybrid methods. In the TPFA-MFD hybrid method, the MFD method is only applied to part of the domain while the TPFA method is applied to rest of the domain. We compared flux accuracy between TPFA and MFD methods by solving a single-phase flow problem. The reference solution is obtained on a rectangular grid while the same problem is solved by TPFA and MFD methods on a grid with distorted cells near a fault. Fluxes computed using TPFA exhibit larger errors in the vicinity of the fault while fluxes computed using MFD are still as accurate as the reference solution. We also compared saturation accuracy of two-phase (oil and water) flow in faulted reservoirs when the pressure equation is solved by different discretization methods. Compared with the reference saturation solution, saturation exhibits non-physical errors near the fault when pressure equation is solved by the TPFA method. Since the MFD method yields accurate fluxes over general polyhedral grids, the resulting saturation solutions match the reference saturation solutions with an enhanced accuracy when the pressure equation is solved by the MFD method. Based on the results of our simulation studies, the accuracy of the TPFA-MFD hybrid method is very close to the accuracy of the MFD method while the TPFA-MFD hybrid method is computationally cheaper than the MFD method.

scholarly journals 3-Dimensional modeling of 2014-Malin Landslide, Maharashtra using satellite-derived data: A quantitative approach to numerical simulation technique

2018 ◽  
Author(s):  
Shovan Lal Chattoraj ◽  
Prashant K. Champati ray ◽  
Sudhakar Pardeshi ◽  
Vikram Gupta ◽  
Yateesh Ketholia
Keyword(s):  
High Resolution ◽  
Debris Flow ◽  
Flow Simulation ◽  
Simulation Models ◽  
Quantitative Information ◽  
Simulation Technique ◽  
Maximum Height ◽  
Deccan Volcanic Province ◽  
South Indian ◽  
High Resolution Satellite Images

Abstract. Debris flows, a type of landslides, are not nowadays limited only to the periodic devastation of the geologically fragile Himalaya but also ubiquitous in weathered Deccan Volcanic Province of the cratonic south Indian peninsula. Comprehensive assessment of landslide hazard, pertinently, requires process-based modeling using simulation methods. Development of precipitation triggered debris flow simulation models of real events are still at a young stage in India, albeit, especially in tectonically less disturbed regions. A highly objective simulation technique has therefore been envisaged herein to model the debris flow run-out happened in Malin. This takes cues from a high- resolution DEM and other ancillary ground data including geotechnical and frictional parameters. The algorithm is based on Voellmy frictional (dry and turbulent frictional coefficients, μ and ξ respectively) parameters of debris flow with pre-defined release area identified on high-resolution satellite images like LISS-IV and Cartosat-1. The model provides critical quantitative information on flow 1) Velocity, 2) Height, 3) Momentum, and 4) Pressure along the entrainment path. The simulated velocity of about 16 m/s at mid-way the slide plummeted to 6.2 m/s at the base with intermittently increased and decreased values. The simulated maximum height was 3.9 m which gradually declined to 1.5 m near the bottom. The results can be beneficial in engineering intervention like the construction of check dams to digest the initial thrust of the flow and other remedial measures designed for vulnerable slope protection.

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