scholarly journals Towards a model for structured mass movements: the OpenLISEM Hazard model 2.0a

2020 ◽  
Author(s):  
Bastian van den Bout ◽  
Theo W. J. van Asch ◽  
Wei Hu ◽  
Chenxiao Tang ◽  
Olga Mavrouli ◽  
...  
Keyword(s):  
Dynamical Behavior ◽  
Mass Movement ◽  
Three Dimensional ◽  
Material Point ◽  
Mass Movements ◽  
Complex Flow ◽  
Flume Experiments ◽  
Stress Strain ◽  
Two Phase ◽  
Flow Equations

Abstract. Mass movements such as debris flows and landslide differ in behavior due to their material properties and internal forces. Models employ generalized multi-phase flow equations to adaptively describe these complex flow types. However, models commonly assume unstructured and fragmented flow after initiation of movement. In this work, existing work on two-phase mass movement equations are extended to include a full stress-strain relationship that allows for runout of (semi-) structured fluid-solid masses. The work provides both the three-dimensional equations and depth-averaged simplifications. The equations are implemented in a hybrid Material Point Method (MPM) which allows for efficient simulation of stress-strain relationships on discrete smooth particles. Using this framework, the developed model is compared to several flume experiments of clay blocks impacting fixed obstacles. Here, both final deposit patterns and fractures compare well to simulations. Additionally, numerical tests are performed to showcase the range of dynamical behavior produced by the model. Important processes such as fracturing, fragmentation and fluid release are captured by the model. While this provides an important step towards complete mass movement models, several new opportunities arise such as ground-water flow descriptions and application to fragmenting mass movements and block-slides.

scholarly journals Towards a model for structured mass movements: the OpenLISEM hazard model 2.0a

2021 ◽  
Vol 14 (4) ◽  
pp. 1841-1864
Author(s):  
Bastian van den Bout ◽  
Theo van Asch ◽  
Wei Hu ◽  
Chenxiao X. Tang ◽  
Olga Mavrouli ◽  
...  
Keyword(s):  
Mass Movement ◽  
Three Dimensional ◽  
Dynamical Behaviour ◽  
Material Point ◽  
Mass Movements ◽  
Complex Flow ◽  
Flume Experiments ◽  
Stress Strain ◽  
Two Phase ◽  
Flow Equations

Abstract. Mass movements such as debris flows and landslides differ in behaviour due to their material properties and internal forces. Models employ generalized multi-phase flow equations to adaptively describe these complex flow types. Such models commonly assume unstructured and fragmented flow, where internal cohesive strength is insignificant. In this work, existing work on two-phase mass movement equations are extended to include a full stress–strain relationship that allows for runout of (semi-)structured fluid–solid masses. The work provides both the three-dimensional equations and depth-averaged simplifications. The equations are implemented in a hybrid material point method (MPM), which allows for efficient simulation of stress–strain relationships on discrete smooth particles. Using this framework, the developed model is compared to several flume experiments of clay blocks impacting fixed obstacles. Here, both final deposit patterns and fractures compare well to simulations. Additionally, numerical tests are performed to showcase the range of dynamical behaviour produced by the model. Important processes such as fracturing, fragmentation and fluid release are captured by the model. While this provides an important step towards complete mass movement models, several new opportunities arise, such as application to fragmenting mass movements and block slides.

Research Analysis and Experiment Study on Flow Field of Hydrodynamic Coupling

2011 ◽  
Vol 418-420 ◽  
pp. 2006-2011
Author(s):  
Rui Zhang ◽  
Cheng Jian Sun ◽  
Yue Wang
Keyword(s):  
Flow Field ◽  
Cfd Simulation ◽  
Two Phase Flow ◽  
Three Dimensional ◽  
Internal Flow ◽  
Phase Flow ◽  
Complex Flow ◽  
Two Phase ◽  
Operation Conditions ◽  
Hydrodynamic Coupling

CFD simulation and PIV test technology provide effective solution for revealing the complex flow of hydrodynamic coupling’s internal flow field. Some articles reported that the combination of CFD simulation and PIV test can be used for analyzing the internal flow field of coupling, and such analysis focuses on one-phase flow. However, most internal flow field of coupling are gas-fluid two-phase flow under the real operation conditions. In order to reflect the gas-fluid two-phase flow of coupling objectively, CFD three-dimensional numerical simulation is conducted under two typical operation conditions. In addition, modern two-dimensional PIV technology is used to test the two-phase flow. This method of combining experiments and simulation presents the characteristics of the flow field when charging ratios are different.

Numerical Analysis of Erosive Wear on the Guide Vanes of a Francis Turbine

2015 ◽  
Vol 741 ◽  
pp. 531-535
Author(s):  
Hong Ming Zhang ◽  
Li Xiang Zhang
Keyword(s):  
Numerical Analysis ◽  
Volume Fraction ◽  
Three Dimensional ◽  
Erosive Wear ◽  
Francis Turbine ◽  
Two Phase ◽  
Guide Vanes ◽  
Flow Equations ◽  
Sand Erosion ◽  
Volume Method

The paper presents the numerical analysis of erosive wear on the guide vanes of a Francis turbine using CFD code. The 3-D turbulent particulate-liquid two-phase flow equations are employed in this study. The computing domain is discretized with a full three-dimensional mesh system of unstructured tetrahedral shapes. The finite volume method is used to solve the governing equations and the pressure-velocity coupling is handled via a Pressure Implicit with Splitting of Operators (PISO) procedure. Simulation results have shown that the volume fraction of sand at the top of the guide vanes is higher than others and the maximum of volume fraction of sand is at same location with the maximum of sand erosion rate density. The erosive wear is more serious at the top of the guide vanes.

Effects of Turbulence on the secondary breakup of droplets in diesel fuel sprays

2020 ◽  
pp. 095440702095858 ◽  
Author(s):  
Hassan Khaleghi ◽  
Hossein Farani Sani ◽  
Masoud Ahmadi ◽  
Faezeh Mohammadzadeh
Keyword(s):  
Three Dimensional ◽  
Droplet Size Distribution ◽  
Computer Code ◽  
Gas Pressure ◽  
Spray Parameters ◽  
Two Phase ◽  
Penetration Length ◽  
Modified Model ◽  
Flow Equations ◽  
Secondary Breakup

In this paper, the importance of turbulence effects on the procedure of droplet’s secondary breakup is studied. In the process of modeling the secondary breakup of a droplet, it is a common practice to presume that the droplet is moving in a laminar flow. However, it is evident that the critical Weber number is profoundly affected by the intensity of turbulence presented in the flow. As a result, the abovementioned supposition may lead to significant computational inaccuracy. This paper tends to perform a modification that considers the effects of turbulent flow on the secondary breakup of droplets. It is shown that the results obtained by the modified model are more precise and in a better agreement with experimental data. In this paper, spray behavior is predicted by a conventional breakup model and the one obtained by a modified model, which are both implemented in an in-house computer code. This CFD code accounts for engine simulation by solving the governing two-phase-flow equations using the Eulerian-Lagrangian approach in a three-dimensional coordinate system. To show the effects of turbulence, the changes in spray parameters such as droplet size distribution, spray tip penetration, and spray mean diameter, which is extracted from the two models are compared. Results have shown that the turbulence causes droplets to break in an earlier time, which leads to a higher rate of evaporation and lower penetration length. An interesting fact concluded in this paper is that the difference between the results of the two models decreases as the gas pressure is increased, which means the effects of turbulence become less important as the gas pressure increases.

Experiment and Numerical Simulation of Rotating Speed of Blade in Sandstone Wastewater of Rotational Flow Grit Chamber

2013 ◽  
Vol 368-370 ◽  
pp. 1868-1871
Author(s):  
Xue Fei Ao ◽  
Xiao Ling Wang ◽  
Zheng Yin Zhou ◽  
Jian Lang
Keyword(s):  
Numerical Simulation ◽  
Removal Efficiency ◽  
Three Dimensional ◽  
Rotational Flow ◽  
Complex Flow ◽  
Two Phase ◽  
Rotating Speed ◽  
Hydroelectric Project ◽  
Scale Experiment ◽  
Collision Force

The high-turbidity solid-liquid two-phase problem of the complex flow pattern is of greatest importance for the grit chamber with rotational flow. An Eulerian-Eulerian two-phase model for describing the collision force between particles in sandstone wastewater properly was developed. A bench scale experiment combining with a hydroelectric project was conducted. By analyzing the removal efficiency at different speeds of blade, the optimized rotating speed was obtained. Based on the optimized rotating speed, three-dimensional numerical simulation of the two-phase flow field was studied. The simulation results showed that when the number of blade is four, the optimum removal efficiency can be reached, which was found to be in reasonable agreement with the experimental data.

scholarly journals Gas–Liquid Two-Phase Flow Investigation of Side Channel Pump: An Application of MUSIG Model

Mathematics ◽  
2020 ◽  
Vol 8 (4) ◽  
pp. 624
Author(s):  
Fan Zhang ◽  
Ke Chen ◽  
Lufeng Zhu ◽  
Desmond Appiah ◽  
Bo Hu ◽  
...  
Keyword(s):  
Two Phase Flow ◽  
Phase Distribution ◽  
Suction Side ◽  
Outer Radius ◽  
Side Channel ◽  
Group Model ◽  
Phase Flow ◽  
Complex Flow ◽  
Two Phase ◽  
Flow Equations

This paper introduces a novel application of a multiphase flow model called the Multi-Size-Group model (MUSIG) to solve 3D complex flow equations in a side channel pump, in order to analyze the flow dynamics of the gas phase distribution and migration under different inlet gas volume fractions (IGVFs). Under different IGVF, the suction side is more likely to concentrate bubbles, especially near the inner radius of the impeller, while there is very little or no gas at the outer radius of the impeller. The diameter of bubbles in the impeller are similar and small for most regions even at IGVF = 6% due to the strong shear turbulence flow which eliminates large bubbles. Additionally, this method also can capture the coalescence and breakage evolution of bubbles. Once a mixture of fluid goes into the impeller from the inlet pipe, the large bubbles immediately break, which accounts for the reason why nearly all side channel pumps have the capacity to deliver gas–liquid two-phase flow. The results in this study provide a foundation and theoretical value for the optimal design of side channel pumps under gas–liquid two-phase conditions to increase their application.

Two-Phase Eulerian/Lagrangian Model for Nucleating Steam Flow

2002 ◽  
Vol 124 (2) ◽  
pp. 465-475 ◽  
Author(s):  
A. G. Gerber
Keyword(s):  
Three Dimensional ◽  
Low Pressure ◽  
Steam Flow ◽  
Nucleation Theory ◽  
Lagrangian Model ◽  
Classical Nucleation Theory ◽  
Navier Stokes ◽  
Steam Turbines ◽  
Complex Flow ◽  
Two Phase

This paper describes an Eulerian/Lagrangian two-phase model for nucleating steam based on classical nucleation theory. The model provides an approach for including spontaneous homogeneous nucleation within a full Navier-Stokes solution scheme where the interaction between the liquid and gas phases for a pure fluid is through appropriately modeled source terms. The method allows for the straightforward inclusion of droplet heat, mass, and momentum transfer models along with nucleation within complex flow systems as found, for example, in low pressure steam turbines. The present paper describes the solution method, emphasizing that the important features of nucleating steam flow are retained through comparison with well-established 1-D solutions for Laval nozzle flows. Results for a two-dimensional cascade blade and three-dimensional low pressure turbine stage are also described.

Numerical Investigation of Sediment-Laden Flow in a High-Head Francis Turbine Runner

2013 ◽  
Vol 860-863 ◽  
pp. 1542-1546
Author(s):  
Hong Ming Zhang ◽  
Li Xiang Zhang
Keyword(s):  
Erosion Rate ◽  
Volume Fraction ◽  
Three Dimensional ◽  
Suction Side ◽  
Francis Turbine ◽  
Two Phase ◽  
Flow Equations ◽  
Maximum Value ◽  
Sand Erosion ◽  
Turbine Runner

The 3-D turbulent particulate-liquid two-phase flow equations are employed in this study. The computing domain is discretized with a full three-dimensional mesh system of unstructured tetrahedral shapes. The finite volume method is used to solve the governing equations and the pressure-velocity coupling is handled via a Pressure Implicit with Splitting of Operators (PISO) procedure. Simulation results have shown that the sand erosion rate on pressure side is more than on the suction side of the blade. The maximum value of sand volume fraction and the maximum value of sand erosion rate are at same location.

Numerical Prediction of Sediment Erosion on Francis Turbine Blades

2013 ◽  
Vol 662 ◽  
pp. 643-647 ◽  
Author(s):  
Hong Ming Zhang ◽  
Li Xiang Zhang
Keyword(s):  
Turbine Blades ◽  
Three Dimensional ◽  
Suction Side ◽  
Numerical Prediction ◽  
Francis Turbine ◽  
Two Phase ◽  
Sediment Erosion ◽  
Flow Equations ◽  
Sand Erosion ◽  
Simulation Results

The paper presents the numerical prediction of sediment erosion on Francis turbine blades using CFD code. The 3-D turbulent particulate-liquid two-phase flow equations are employed in this study. The computing domain is discretized with a full three-dimensional mesh system of unstructured tetrahedral shapes. The finite volume method is used to solve the governing equations and the pressure-velocity coupling is handled via a Pressure Implicit with Splitting of Operators (PISO) procedure. Simulation results have shown that the sand erosion rate on pressure side is more than on the suction side of the blade. The numerical simulation results are consistent with the real situation.

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