scholarly journals Estimation of flow velocity for a debris flow via the two-phase fluid model

2014 ◽  
Vol 1 (1) ◽  
pp. 999-1021
Author(s):  
S. Guo ◽  
P. Xu ◽  
Z. Zheng ◽  
Y. Gao
Keyword(s):  
Debris Flow ◽  
Real World ◽  
Empirical Formula ◽  
Debris Flows ◽  
Fluid Model ◽  
Two Phase ◽  
Liquid Phases ◽  
Two Phases ◽  
Phase Fluid ◽  
Steady Velocity

Abstract. The two-phase fluid model is applied in this study to calculate the steady velocity of a debris flow along a channel bed. By using the momentum equations of the solid and liquid phases in the debris flow together with an empirical formula to describe the interaction between two phases, the steady velocities of the solid and liquid phases are obtained theoretically. The comparison of those velocities obtained by the proposed method with the observed velocities of two real-world debris flows shows that the proposed method can estimate accurately the velocity for a debris flow.

scholarly journals Estimation of flow velocity for a debris flow via the two-phase fluid model

2015 ◽  
Vol 22 (1) ◽  
pp. 109-116 ◽  
Author(s):  
S. Guo ◽  
P. Xu ◽  
Z. Zheng ◽  
Y. Gao
Keyword(s):  
Debris Flow ◽  
Real World ◽  
Empirical Formula ◽  
Debris Flows ◽  
Fluid Model ◽  
Two Phase ◽  
Liquid Phases ◽  
Two Phases ◽  
Phase Fluid ◽  
Steady Velocity

Abstract. The two-phase fluid model is applied in this study to calculate the steady velocity of a debris flow along a channel bed. By using the momentum equations of the solid and liquid phases in the debris flow together with an empirical formula to describe the interaction between two phases, the steady velocities of the solid and liquid phases are obtained theoretically. The comparison of those velocities obtained by the proposed method with the observed velocities of two real-world debris flows shows that the proposed method can estimate the velocity for a debris flow.

A two-fluid model for avalanche and debris flows

2005 ◽  
Vol 363 (1832) ◽  
pp. 1573-1601 ◽  
Author(s):  
E. Bruce Pitman ◽  
Long Le
Keyword(s):  
Debris Flows ◽  
Fluid Model ◽  
Solid Material ◽  
Fluid Inertia ◽  
Two Phase ◽  
Engineering Research ◽  
Mass Flows ◽  
Two Fluid Model ◽  
Two Fluid ◽  
Geophysical Mass Flows

Geophysical mass flows—debris flows, avalanches, landslides—can contain O (10 6 –10 10 ) m 3 or more of material, often a mixture of soil and rocks with a significant quantity of interstitial fluid. These flows can be tens of meters in depth and hundreds of meters in length. The range of scales and the rheology of this mixture presents significant modelling and computational challenges. This paper describes a depth-averaged ‘thin layer’ model of geophysical mass flows containing a mixture of solid material and fluid. The model is derived from a ‘two-phase’ or ‘two-fluid’ system of equations commonly used in engineering research. Phenomenological modelling and depth averaging combine to yield a tractable set of equations, a hyperbolic system that describes the motion of the two constituent phases. If the fluid inertia is small, a reduced model system that is easier to solve may be derived.

scholarly journals Tiny Bubbles

2009 ◽  
Vol 17 (1) ◽  
pp. 3-5
Author(s):  
Stephen W. Carmichael
Keyword(s):  
Lower Energy ◽  
Critical Role ◽  
Interfacial Area ◽  
Consumer Products ◽  
Phase System ◽  
Two Phase ◽  
Liquid Phases ◽  
Phase Systems ◽  
Two Phases

This is not an article about the song made famous by the late (great) Don Ho. This is about a breakthrough in the understanding of how micrometer-sized bubbles can be stabilized for long periods of time. This can influence the taste, smell, and consistency of consumer products including food and cosmetics.In two-phase systems, which can include air (as bubbles) suspended within a liquid, the structures of the dispersed (bubbles) and continuous (liquid) phases play a critical role in determining the properties of the material. There is also the function of time in that the microstructure of the dispersed phase continuously evolves toward a state of lower energy by minimizing the surface area between the two phases (referred to as the interfacial area). In the long term, this time evolution diminishes the usefulness of two-phase systems. Emilie Dressaire, Rodney Bee, David Bell, Alex Lips, and Howard Stone have devised a way to stabilize a two-phase system for time periods of a year or longer.

Reactor Safety Analysis Based on a Developed Two-Phase Compressible Flow Simulation

Volume 1 ◽  
2004 ◽  
Author(s):  
A. F. Nowakowski ◽  
B. V. Librovich ◽  
L. Lue
Keyword(s):  
Multiphase Flow ◽  
Compressible Flow ◽  
Fluid Model ◽  
Numerical Technique ◽  
Computational Simulation ◽  
Safety Analysis ◽  
State Equations ◽  
Pressure Relief ◽  
Two Phase ◽  
Two Phases

The direct numerical simulation of multiphase flow is a challenging research topic with various key applications. In the present work, a computational simulation of multi-phase compressible flow has been proposed for safety analysis of chemical reactors. The main objective of a pressure relief system is to prevent accidents occurring from over pressurisation of the reactor. We are particularly interested in understanding the phenomena associated with emergency pressure relief systems for batch-type reactors and storage vessels. Existence of multiphase flow is significantly influenced by the interface between the phases and the associated discontinuities across the phase. The approach, which builds on the method first introduced by Saurel and Abgrall [1], was developed for solving two-phase compressible flow problems. Each phase is separately described by conservation equations. The interactions between two phases appear in the basic equations as transfer terms across the interface. The equations are complemented by state equations for the two phases and by additional correlations for the right-hand side coupling terms. The method is able to deal with multiphase mixtures and interface problems between compressible fluids. The key difference compared to classical two-fluid model is the presence of separate pressures fields associated with phases and introduction of pressure and velocity relaxation procedures. The relaxation operators tackle the boundary conditions at the interface and consequently the model is valid for fluid mixtures, as well as for pure fluids. The numerical technique requires the system to be decomposed and involves a non-conservative hyperbolic solver, an instantaneous pressure relaxation procedure and source term operators. The solution is obtained by succession of integrators using a second-order accurate scheme. The ultimate goal of this research is to use the method for studying the venting problem in reactor systems after verifying its performance on a series of standardised test cases documented in the literature.

A two-phase fluid model of crystal settling under variable gravity

1999 ◽  
Author(s):  
A. Alexandrou ◽  
H. Shi ◽  
N. Gatsonis ◽  
A. Sacco, Jr.
Keyword(s):  
Fluid Model ◽  
Two Phase ◽  
Crystal Settling ◽  
Variable Gravity ◽  
Phase Fluid

A Theory of Electrophoresis of Emulsion Drops in Aqueous Two-Phase Polymer Systems

1981 ◽  
Vol 9 ◽  
Author(s):  
Samuel Levine
Keyword(s):  
Continuous Phase ◽  
Immiscible Liquid ◽  
Ion Distribution ◽  
Two Phase ◽  
Relaxation Effects ◽  
Liquid Phases ◽  
Increase With Increase ◽  
Aqueous Mixture ◽  
Idealised Model ◽  
Two Phases

ABSTRACTTwo immiscible liquid phases form when an aqueous mixture of the electrically neutral polymers dextran and polyethylene glycol are equilibrated at sufficient concentrations. Certain supporting electrolytes which contain sulphate, phosphate or citrate ions partition unequally between the phases, and in their presence, electrophoresis of a drop of one phase suspended in the other is observed, with large mobilities. These mobilities depend linearly on the radius of the drop and the direction of the drop's motion is reversed when the disperse phase and the continuous phase are interchanged. When those ions which produce electrophoresis are present the potential Implied by the direction of electrophoresis is opposite to the Donnan potential observed between the two phases. To explain these results, we postulate an electric dipole layer associated with a mixture of oriented polymer molecules at the surface of a drop. In addition, a potential difference between the interiors of the two phases results from the unequal ion distribution. For the idealised model of a surface layer of point dipoles the inner and outer diffuse layers carry net charges equal in magnitude but opposite in sign. The classical theory of electrophoresis due to Henry, Overbeek and Booth is adapted to the motion of an emulsion drop under an electric field when diffuse ionic layers are present inside and outside the drop. Relaxation effects are treated for the case where the two diffuse layer thicknesses are small compared with the drop radius. An expression is obtained for the electrophoretic mobility of a drop which depends linearly on radius and also shows an increase with increase in salt concentration. The theory presented here is related to the work of Levich.

Effect of Pressure on Two-Phase Modeling for Viscous Potential Flow

2013 ◽  
Author(s):  
Somayeh Ahmadi
Keyword(s):  
Potential Flow ◽  
Fluid Model ◽  
Computational Stability ◽  
Two Phase ◽  
Viscous Potential Flow ◽  
Pressure Correction ◽  
Effect Of Pressure ◽  
Correction Scheme ◽  
Two Fluid Model ◽  
Two Phases

In this study, the effect of pressure on the disturbed interface for two-phase stratified regime will be discussed. It is assumed that the two phases are in potential flow condition, a pressure correction algorithm for the two-fluid model is carefully implemented to minimize its effect on numerical stability. Numerical analysis is applied using the finite difference method. Actually pressure correction scheme is employed to solve the viscous potential flow model. It is designed to increase the computational stability when the flow is near the ill-posedness condition. The viscous potential flow theory fits the only pressure experimental data for air and water well.

A FRACTAL TWO-PHASE FLOW MODEL FOR THE FIBER MOTION IN A POLYMER FILLING PROCESS

Fractals ◽  
2020 ◽  
Vol 28 (05) ◽  
pp. 2050093 ◽  
Author(s):  
XUEJUAN LI ◽  
ZHI LIU ◽  
JI-HUAN HE
Keyword(s):  
Fiber Orientation ◽  
Fluid Model ◽  
Polymer Melt ◽  
Element Model ◽  
Filling Process ◽  
Governing Equations ◽  
Two Phase ◽  
Fiber Motion ◽  
Fractal Space ◽  
Phase Fluid

This paper suggests a fractal two-phase fluid model for the polymer melt filling process to deal effectively with the unsmooth front interface. An infinitesimal fluid element model in a fractal space is proposed to establish the governing equations according to the conservation laws in fluid mechanics, the fractal divergence and fractal Laplace operator are defined. The unsmooth interface is solved numerically, and fibers’ motion properties on the interface are also elucidated. Moreover, the distribution of fibers on the interface at different stages shows the fractal property of the fibers’ motion. However, the motion of fibers is affected by the flow of macroscopic polymer melt, and the fiber orientation in the interface shows a certain statistical regularity. Based on the characters of fiber orientation, the fractal interface can be used for the optimal design of the polymer melt filling process.

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